Floriculture Greenhouse Update

Greenhouse tomatoes are usually scheduled to come into production when field tomatoes are not available. In Northern sections of the country, such as New England, the field production season occurs late in the summer and is short in duration. As a result, greenhouse tomato growers in New England, find they can market greenhouse tomatoes through most of the summer and still get a good price. The time interval between sowing a crop and harvesting ripe fruit will vary with the season since the rate of seedling and fruit development are affected by temperature. Light during seedling development will also affect the timing of initial flowering. Under ideal conditions, high light and warm temperatures, it will take about eight (8) weeks from seeding until the first flowers open and another eight (8) weeks from flowering until first harvest. Seedlings are generally transplanted into the production greenhouse 2-3 weeks before flowering. During less than ideal conditions the period from seed to harvest will be longer than 16 weeks. Use the schedules listed below as a general guide. Remember the actual time required will vary between cultivars and with the light and temperature conditions in your greenhouse.

Crop season, Development stage, Time interval, Weeks from seed

Early Spring Seed: Oct 25-Nov 25 Transplant: Jan 1-Jan 15, Weeks from seed: 9-10 Harvest: April 1-July, Weeks from seed: 22-23Late spring Seed: Dec 15-Jan 15 Transplant: Feb 1-March 1, Weeks from seed: 6-7 Harvest: May 1-July, Weeks from seed: 19-20Fall Seed: June: 15-July 15Transplant: July 20-Aug 15, Weeks from seed: 5 Harvest: Oct 1-Dec, Weeks from seed: 16

Richard McAvoyPlant Science Department, University of Connecticut

Links to presentations and handouts from Greenhouse and High Tunnel Tomato Conference held November 2009.

Fall mums will exhibit signs of wilting during extended periods of 90 plus degree temperatures. The solution may not be as easy as turning on the irrigation.Fall mums wilt when the soil is dry, but wilting will also occur in hot weather which may cause plants to be stressed, or if the roots are damage from a root disease such as Pythium, even if the soil is saturated with water. When the roots stop functioning normally the plants will show signs of stress by wilting.

Keep in mind fall mums can survive excess amounts of fertilizer and resulting soluble salts when temperatures are normal and soil moisture is maintained. Problems occur when the growing medium is dry and the salts become more concentrated, resulting in root damage. The plants will react first by wilting and than collapsing.

Take precautions to avoid overwater garden mums especially during periods of hot weather like this week.  Lift the pots and check the roots periodically. If the pots feel heavy and the soil is saturated, do not irrigate, even if it is hot. However, do not allow plants to dry to wilt prior to watering.

If plants are wilting on a regular basis and excess amounts of fertilizer have been used, the roots maybe damaged and root disease will occur. Check the plant roots, especially with slower growing varieties. The roots tell a lot about a plants health, often before the top growth shows symptoms.

Paul Lopes, Tina SmithUniversity of Massachusetts Extension

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Fall mums will exhibit signs of wilting during extended periods of 90 plus degree temperatures. The solution may not be as easy as turning on the irrigation.

Fall mums wilt when the soil is dry, but wilting will also occur in hot weather when the soil is saturated with water, and/or if the roots are damage from a root disease such as pythium. When the roots stop functioning normally the plants will show signs of stress.

Keep in mind fall mums can survive excess amounts of fertilizer and resulting soluble salts when temperatures are normal and soil moisture is maintained. Problems occur when the growing medium is dry and the salts become more concentrated, resulting in root damage. The plants will react first by wilting and than collapsing.

Take precautions to avoid overwater garden mums especially during periods of hot weather like this week.  Lift the pots and check the roots periodically. If the pots feel heavy and the soil is saturated, do not irrigate, even if it is hot. However, do not allow plants to dry to wilt prior to watering. If plants are allowed to wilt on a regular basis when controlled release fertilizer is used, the roots may burn and root disease will occur. Check the plant roots, especially slower growing varieties. The roots tell a lot about plant health, many times before the top growth shows symptoms.

Viburnum leaf beetles are becoming active in nurseries and retail garden centers. See information and photos: Viburnum Leaf Beetle UMass and Cornell

High temperature is one of the most important factors to control in the retail yard. Shading and air movement are ways to help keep temperatures cooler for plants in the retail setting. The use of 50% shade of the midday sunlight will reduce light to appropriate levels. See the fact sheet Caring for plants in retail settings: 

Two-spotted spider mites are showing up on Ipomoea. See message and photos on managing mites.

Spittlebugs: The white foam from spittlebugs can be seen now on many perennials as the spittlebugs move in from grassy areas. Most of the damage is cosmetic only and does not harm the plant. If the infestation is small, either handpick the spittle masses with a gloved hand or use a forceful jet of water to dislodge the nymphs. For more information and photo see this previous message.

Plant nutrition: Bedding plants in retail yards may be showing signs of lack of feed. With the recent prolonged high temperatures and frequent watering, fertilizer may have leached out. If new growth is yellowing and roots are healthy, fertilize with 200 ppm of a complete fertilizer such as 20-10-20 at every watering. Bedding plants usually recover easily because they are quickly purchased, and are planted out in the garden, fertilized and have room to grow.

Hanging baskets and patio pots are a different story. Plants in hanging baskets and planters will stay in those containers throughout the summer. The small volume of soil in a container is the only available source of nutrients for the plant compared to the much larger volume of soil available to the plants in a garden. Frequent watering causes much of the fertilizer to be leached out. If hanging baskets and planters are not fertilized in the retail sales area, or if controlled-release fertilizer was not used, all the fertilizer will leach out by the time the consumer buys the plants. The plants will quickly decline in quality once the customer takes the basket home. There are solutions. One is to fertilize baskets and planters in the retail sales area, on a weekly basis, using 400 ppm N, or using 200 ppm N at every watering. Another solution is to top-dress the basket or planter with a controlled- release fertilizer using 3-5 grams of N of a shorter term, 4-6 month material or use tablets according to directions. Retailers should communicate with their wholesale growers to make sure controlled-release fertilizer has not already been applied prior to shipping before fertilizing plants.

Tomato plants: Monitor for late blight and bacterial canker. See message.

Garden Mums should be planted as soon as possible upon arrival. See the message  about early season care including fertilizing and crown buds.

Tina Smith, University of MassachusettsLeanne Pundt, University of ConnecticutPaul Lopes, University of Massachusetts

Mum cuttings are arriving at some growers. Begin the season by reviewing your fertilizer program and teaching new employees to recognize Chrysanthemum white rust symptoms.

Mums are heavy feeders during the first few weeks. Growers use a variety of ways to fertilize mums. Some growers use 100% water soluble fertilizer through a drip system, some use 100% controlled-release fertilizer and some use a combination of water soluble and controlled-release. Regardless of the program you use, start plants off right and prevent premature buds by:

Using moistened soil when potting up plants, then water-in freshly planted cuttings with a fertilizer solution. Many growers are successfully using 200 to 300 ppm of 20-20-20 immediately after planting. The cuttings establish faster and grow more rapidly.

Do not stress the young plants during their first 4 to 5 weeks of growth, and especially during the first 10 days of the crop or plants will develop buds prematurely and plants will be short. Keep plants moist, well fertilized and properly spaced.

Also check plant roots regularly to monitor plant health.

To encourage soft growth that branches freely, many growers use 250-300 ppm 20-20-20 or a fertilizer that is at least 60% ammonical nitrogen as a constant feed during the first 2-3 weeks for all fertilizer programs. Then, growers using 100% water soluble fertilizer throughout the season, switch to 200-250 ppm 20-10-20 constant feed for 3-4 applications and then rotate to a calcium nitrate based fertilizer such as 15-0-15 for 1 application, then repeat. The 20-10-20 contains less ammonical nitrogen. Once plants start to show color, fertilizer is reduced to 100 ppm constant feed.

If using controlled-release fertilizer, keep in mind that the rate of release is affected by its formulation (rate of release), soil temperature and frequency of irrigation. Most formulations release at temperatures of 70°F or above, therefore during cool temperatures, fertilizer is going to be slow to release. We often have cool temperatures in June when plants need the most fertilizer. This is the reason liquid feed becomes important, to get plants growing and create vegetative growth.

Garden mums initiate flower buds easily and develop rapidly if plants are stressed in any way. If terminal flower buds are observed when cuttings arrive, plants should still perform satisfactorily. When cuttings with terminal flower buds are planted, they should be pinched hard (allow 4-5 leaves to remain) when they are turgid (4-5 days after planting). This will force out lower breaks which tend to be more vegetative. If both terminal and lateral buds have developed when cuttings arrive, it is best not to plant them, as they most likely will not perform satisfactorily.

Tina Smith, University of Massachusetts

For more information see:

Fact Sheet: Garden Mums for Fall Sales. University of MassachusettsFact Sheet 2008: Chrysanthemum White Rust. University of Massachusetts.Grolink: Belgian Mum Cultural Information Fact Sheet. Garden Mums from Cell Paks. Griffin Greenhouse Supply Company.

‘Tis the season for extreme temperatures. Monitor the weather forecast and avoid moving cold tolerant annuals and herbaceous perennials outdoors if a hard frost (colder than 28°F) is predicted at any point within at least three nights of when plants would be put outside. Avoid placing plants in low-lying areas because frost will more likely settle in these areas. Be prepared to cover plants if temperatures go below 28°F.

While herbaceous perennials and cool tolerant annuals, can be displayed or grown outdoors, they need to be acclimated or hardened off first. Cool tolerant crops include pansy, annual phlox, alyssum, osteospermum, nemesia, calibrachoa, verbena, diascia, bidens, antirrhinum (snapdragon), mimulus, lobelia and petunias.

Begin with just a few plants and experiment with cultivars, making adjustments as needed. Some varieties of the same type of plant have varying degrees of cold hardiness. Learning which plants perform best will take some experimenting.

Plants will adapt best to cooler temperatures when they have been started at optimum growing temperatures and have a well-established root system. Once plants get to their desired size, lower the greenhouse temperatures to 45° - 55°F for at least a week to acclimate them for outdoors.

Botryis blight and lack of fertilizer are two common problems which occur with outdoor growing. To prevent Botrytis, water plants in the morning and let the foliage dry before night. Plants growing outdoors may require less water and less frequent irrigation and this means that plants are fertilized less often. Although plants are being grown cool, it is important to continue to fertilize plants and maintain proper fertility. Pay particular attention during rainy periods, (like this weekend) and monitor plants for both Botrytis and nutrient leaching.

Cool media temperatures also increase the risk of root rots caused by Pythium, Rhizoctonia and Thielaviopsis. Regularly monitor roots for disease and apply fungicides early. Fungicides work more slowly in cool media. It may take longer to see results of an application or an application may be less effective.

Without some sort of protection, you are always taking a chance when growing outdoors in early spring and occasionally plants will get damaged. By choosing cool tolerant plants, acclimating plants, closely watching weather forecasts and providing extra protection when needed, you will minimize the risk, grow higher quality plants and provide an extra turn in production.

Fact Sheet: Moving Cool Tolerant Plants Outdoors: Risks and Benefits Link to: Proven Winner outdoor growing guidelines

Tina Smith, UMass ExtensionLeanne Pundt, UConn Extension

While some growers clean and re-use pots, trays and flats and it is important to do it properly. Plant pathogens such as Pythium, Rhizoctonia and Thielaviopsis can survive in root debris or soil particles on greenhouse surfaces. If the previous crop had a disease problem, then avoid re-using those containers. It is also a good idea to avoid planting crops that are prone to Thielaviopsis problems, like pansies, in containers that have been previously used.

All containers should be washed thoroughly to remove soil particles and plant debris before being treated with a greenhouse disinfectant, even if there was no evidence of disease in the crop. Debris and organic matter can protect pathogen spores from coming in contact with the disinfectant solution.

There are several products available for disinfecting surfaces including quaternary ammonium products (Greenshield®, Physan 20™, Triathlon®), and hydrogen dioxide (ZeroTol®, OxiDate®). Follow label directions for these products - labels indicate that pots must be soaked for at least 10 minutes in these products to be fully effective. A 10 percent solution of household chlorine bleach (one part bleach to 9 parts of water) may be used for pots and flats, but the solution has a shorter activity period than other disinfectants, losing half its strength in 2 hours. Chlorine bleach is also phytotoxic to some plants, and must be used in a well-ventilated area to protect workers

Fact Sheet: Cleaning and Disinfecting the Greenhouse

New England Greenhouse Floriculture Guide (ordering information)

Tina Smith, UMass Extension

 

 

It is best to clean greenhouses as they become empty rather than to wait until just prior to the spring growing season. Cleaning early will eliminate over-wintering sites for pests and reduce populations for the next crop cycle. Greenhouse pests will overwinter in weeds and protected areas in unheated greenhouse, especially if the winter is unseasonably warm. Remove leftover plants and debris and clean the floor of soil, organic matter and weeds. Clean areas around furnaces and along side walls where small weeds are usually found. Use weed barriers, repair tears in worn weed barriers and do not use stone on top. Stone will trap soil and moisture and create an ideal environment for weeds, diseases, insects and algae. It is also a good time to correct any drainage problems and low spots in greenhouses.

Next, disinfect the growing and plant handling areas, and irrigation system. There are several different types of disinfectants that are currently used in the greenhouse for plant pathogen and algae control including quaternary ammonium compounds (Green-Shield®, Physan 20®, and Triathlon®), hydrogen dioxide (ZeroTol®, Oxidate®), chlorine dioxide (Selectrocide), hydrogen peroxide plus peroxyacetic acid (ScaniDate) and sodium carbonate peroxydrate (Green Clean Pro®, TerraCyte®). All these products have different properties, so read and follow label directions. Chlorine bleach may be used for pots or flats, but is not approved for application to walls, benches or flooring. Alcohol is flammable and therefore not used as a general disinfectant. However, it is useful as a dip or swipe treatment to disinfect propagation tools. If possible, disinfectants should be used on a routine basis both as part of a pre-crop clean-up program and during the cropping cycle.

Organic growers have limited options for disinfectants. Oxidate® is the only material mentioned above that is currently listed by the Organic Material Review Institutes (OMRI), see www.omri.org. Ethyl or isopropyl alcohol is also allowed under the organic standards. Organic growers should always check with their certifying organization before using any material new in their farming practices.

Fact Sheet: Cleaning and Disinfecting the Greenhouse 

2009-2010 New England Greenhouse Floriculture Guide (ordering information)

Tina Smith, UMass Extension

 

Many growers are reporting that mums are shorter and are flowering earlier this season. Cool temperatures,cloudy and rainy weather have been the norm this summer. Take advantage of sunny days to fertilize plants.

Premature budding Chrysanthemum flower buds initiate easily and develop rapidly, especially if plants are stressed in any way. Lack of adequate fertilizer and cool nights are causes for premature budding. When grown outdoors, we are relying on natural daylength and temperature to control the timing of the crop. Chrysanthemums are short-day plants. Both flower initiation and development of the flower buds occur more rapidly under short days than in long days. However, temperature has a greater influence than daylength on flowering of garden mums. With several cool nights in a row, garden mums can initiate many buds prematurely which results in early flowering of plants.

Short plants. Again, short plants are a result of plants setting bud too early. In chrysanthemums, flower bud initiation marks the end of vegetative growth. Garden mums initiate leaves rapidly. Cool weather early in the growing season will reduce the number of leaves formed on each shoot, thereby, resulting in plants with fewer nodes and shorter plants. Another reason for smaller, harder plants may be due to lack of nutrients. Frequent rain made it difficult to keep plants fertilized. As a result, nutrients were leached and plants stopped growing.

How growers responded. Some growers pinched buds off of plants (in July) and fertilized more often with higher rates (350 ppm) to allow plants to grow larger and flower later. This may not work for very early and early flowering varieties that are programmed to flower early.

Some growers left buds on plants and fertilized with up to 400 ppm nitrogen of 20-10-20. Some growers even included ammonium forms of nitrogen (20-20-20) in their fertilizer program. The theory being that vegetative growth would by-pass the budded growth. In some cases this has worked while for most it resulted in uneven plants with short, budded or flowering plants surrounded by some tall growth, but not enough to fill out the plant, creating two-tiered plants. Growers also reported that the plant’s response has varied according to the variety.

At this time, mums should receive constant feed of 300 ppm nitrogen from fertilizers like 20-10-20 to promote vegetative growth. Reapply up to 400 ppm after each rain to keep sufficient nutrient levels. Note that root health should be monitored.  Diseased roots will not take up fertilizer.

Final note: Some growers have asked about using Fascination [a cocktail of two plant hormones, gibberellic acid (GA4+7) and benzyladenine (BA) in equalproportions] to increase plant height. Fascination increases height by stretching the distance between the leaves. Trials using Fascination on poinsettias have shown that it will stretch soft tissue about an inch per application. Response is quick, within one week of application you will know how much additional growth the treatment produced.  Application can be repeated as needed but results are best when shoot growth is still soft and several of the upper internodes have not yet expanded. Once stems harden they will be less responsive to treatment and late treatments may just cause the flower buds to stretch above the foliage. Trials using Fascination on garden mums has been minimal at this time but preliminary results show increased stem length with a 10ppm spray application. 

For more information (and photo) of Fascination on mums: GroLink July Newsletter

Tina Smith, University of Massachusetts Rich McAvoy, University of Connecticut

Plants on display in your garden center or farm stand require regular, gentle watering to maintain high quality. Watering should be completed during the daylight hours, to allow plants to dry before dark. The drying will help prevent foliar diseases. If plants are to be watered by hand, be sure to furnish sufficient time and personnel to water thoroughly. Anything less, and plant quality will decline rapidly.

Place hanging baskets in areas beside the aisles, not over aisles where water and fertilizer will drip onto customers and create a hazard.

Keep plants and surrounding areas in order and clean even during the busiest times. Removing dead and injured plants and spent flowers are essential at least twice a day even during the busy season. Customers get turned off when plants look bad and high ethylene concentrations from decaying plant tissue will causes premature loss of foliage and flowers. A skilled employee isn’t necessary for these jobs, but a competent one is. Employees should carry pruning shears and wear work aprons with large pockets where they can keep dead flowers and debris from plants in the sales area until they can find a waste can.

Plants in hanging baskets and planters will stay in those containers throughout the summer and will need to be fertilized in a retail operation. Depending on the plants, options include fertilizing on a weekly basis, using 400 ppm N or 200 ppm N at every watering or topdressing with a controlled- release fertilizer according to directions. Retailers should communicate with their wholesale growers to make sure controlled-release fertilizer has not already been applied prior to shipping.

Potted plants and bedding plants left over after the busy weekend will also need fertilizing, especially if they have been irrigated and spot watered with only plain water for several days. Inspect the root health and if healthy, fertilize, using 200 ppm N. Poor root health may indicate a need for a fungicide application.

Fact Sheet: Caring for Plants in the Retail Setting

Paul Lopes, University of Massachusetts Tina Smith, University of Massachusetts

 

Cool, cloudy or rainy weather creates an ideal environment for Botrytis infections during production in a full greenhouse.

Once Botrytis develops, it cannot be effectively controlled with fungicides alone. The key to suppressing Botrytis is to keep the plant canopy dry especially from dusk until dawn. This can be accomplished by managing the greenhouse environment. Ventilation allows the exchange of moist greenhouse air with drier air from outdoors. Heating is necessary to bring outdoor air up to optimum growing temperature, and also increases the capacity of the air to carry moisture, thus avoiding condensation. Neither practice alone is as efficient as both combined.

The method and time it takes for heating and venting will vary according to the heating and ventilation system in the greenhouse. To vent the humid air in greenhouses with vents, the heat should be turned on and the vents crack open an inch or so. When doing this the warmed air will hold more moisture (RH), escape from the greenhouse through the vents and be replaced with outside air of lower RH. This natural rising of the air will result in a greenhouse of lower relative humidity.

In houses with fans, the fans should be activated and operated for a few minutes and than the heater turned on to bring the air temperature up. The fans should then be shut off. A clock could be set to activate the fans. A relay may be needed to lock out the furnace or boiler until the fans shut off so that both the fans and heating system do not operate at the same time and flue gases are not drawn into the greenhouse.

The venting and heating cycle should be done two or three times per hour during the evening after the sun goes down and early in the morning at sunrise. The time it takes to exchange one volume of air depends on several factors including whether or not fans are used and, the size of the fans and vents. For some greenhouses it may take as little as 2-3 minutes air exchange. For greenhouses using natural ventilation, it may take 30 minutes or longer. Heating and venting can be effective even if it is cool and raining outside. Air at 50°F and 100% RH (raining) contains only half as much moisture as the greenhouse air at 70°F and 95% RH.

For more information Reducing Humidity in the Greenhouse New England Recommendation Guide

Tina Smith, University of Massachusetts Leanne Pundt, University of Connecticut

 

Welcome to the New England Greenhouse Update

Welcome to the New England Greenhouse Update for commercial growers of greenhouse crops and flowers. University Extension Specialists contribute information to this website from current observations at greenhouses in Massachusetts, Connecticut and Rhode Island.

Your observations and experiences are welcome. Please contact Tina, Leanne or Paul to have information posted on our website.

The University of Massachusetts and University of Connecticut Extension Floriculture Programs support the greenhouse industry with researched based information on environmentally safe production practices. Educational activities include newsletters, publications, workshops, conferences, training programs, diagnostic services and research.

For more information see the University of Massachusetts Extension Floriculture Program website and the University of Connecticut Integrated Pest Management website.

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Click here to view the Greenhouse Update. This section is updated with timely information to help keep you informed.

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The weekend weather forecast calls for sunny days with temperatures in the mid to high 80’s following this week of cool, cloudy weather. As a result, there is a strong possibility, your spring crops will experience summer temperatures in a greenhouse with little or no shading in place. Even one or two days of bright sunshine with temperatures in the high 80’s can stress bedding plants and hangers with rooting systems that are not fully developed. Delicate foliage of shade plants such as impatiens will be susceptible to sunburn.

Be sure your greenhouses are well ventilated and the crops are irrigated to avoid wilting and undue stress on the crops. Shade cloth may be needed over areas containing shade plants.

Photo: Impatiens showing stress

Sunscald on Basil

Tina Smith, Paul Lopes, University of Massachusetts

Growers can free up greenhouse space, by safely moving cool tolerant plants outdoors early. This space can be then be refilled with another crop. In addition to saving growing space, plants grown at cool temperatures “harden off” or acclimate allowing retailers to display plants safely outdoors earlier providing a greater selection of plants for early spring sales.

How well plants finish outdoors depends on the genetic cold tolerance of the plants, the air movement around plants, how well plants are acclimated and how well the plants are maintained, once outdoors. Tropical and subtropical warm crops such as alternanthera, angelonia, New Guinea impatiens, lantana, vinca, celosia, cleome, coleus, cosmos, gomphrena, ipomoea, melampodium, portulaca, sunflowers, zinnias, tomatoes, peppers and squash plants are naturally sensitive to cool temperatures and are not a good choice for early spring outdoor yards.

Herbaceous perennials and cool tolerant annuals, however, can be grown outdoors, but need to be acclimated or hardened off first. Cool tolerant crops to try include pansy, annual phlox, alyssum, osteospermum, nemesia, calibrachoa, verbena, diascia, bidens, antirrhinum (snapdragon), mimulus, lobelia and petunias.

Begin with just a few plants for outside production and experiment with cultivars, making adjustments as needed. Some varieties of the same type of plant have varying degrees of cold hardiness. Learning which plants perform best will take some experimenting.

Plants will adapt best to cooler temperatures when they have been started at optimum growing tempertures and have a well-established root system. Once plants get to their desired size, lower the greenhouse temperatures to 45° - 55°F for at least a week to acclimate them for outdoors.

Monitor the weather forecast and avoid moving plants outdoors if a hard frost (colder than 28°F) is predicted at any point within at least three nights of when plants would be put outside. Avoid placing plants in low-lying areas because frost will more likely settle in these areas.

Botryis blight and lack of fertilizer are two common problems which occur with outdoor growing. To prevent Botrytis, water plants in the morning and let the foliage dry before night. Plants growing outdoors may require less water and less frequent irrigation and this means that plants are fertilized less often. Although plants are being grown cool, it is important to continue to fertilize plants and maintain proper fertility. Pay particular attention during rainy periods and monitor plants for both Botrytis and nutrient leaching.

Cool media temperatures also increase the risk of root rots caused by Pythium, Rhizoctonia and Thielaviopsis. Regularly monitor roots for disease and apply fungicides early. Fungicides will work more slowly in cool media. It may take longer to see results of an application or an application may be less effective.

Be prepared to cover plants if temperatures go below 28°F. An over-wintering thermo blanket such as polyethylene or polypropylene foam can be used for this purpose.

Fact Sheet: Moving Cool Tolerant Plants Outdoors: Risks and Benefits Link to: Proven Winner outdoor growing guidelines

Tina Smith, UMass

Allow newly arrived pre-finished plants to recover from shipping stress and to initiate active root growth (about 1-2 weeks) prior to transplanting into the final-sized pot. Hydrangea blooms are formed on the previous year's growth, so the flowers are already in place in the dormant buds. The ideal starting temperature for hydrangeas is a 60 to 62°F soil temperature supplied with bottom heat, while maintaining slightly cooler air temperatures (about 58°F). This allows root activity prior to bud opening on the shoots. Grow plants slightly on the "dry side" prior to transplanting to prevent root rot and to encourage root development. Avoid fertilizing until root activity has occurred.

One of the main problems with hydrangeas is poor root establishment which leads to water stress during late stages of forcing. To prevent this, several sources recommend slitting the root ball to form an X, when transplanting, opening the sections and placing in direct contact with the growing media in the pot.

To ensure clear pink or blue inflorescences, order cultivars programmed for the desired color and continue the color program throughout forcing. Fertilization practices during the previous summer growth phase influences coloration during forcing, and changing the color program during the forcing phase can result in shades of mauve tones.

Whether a hydrangea (excluding white cultivars) develops a pink or blue inflorescence is dependent on the presence and availability of aluminum. The absence of aluminum assures pink flowers; high availability of aluminum leads to blue flowers. By regulating aluminum, flower color can be controlled.

Pink Flowers Avoid supplying aluminum to plants and use fertilizers that do not contain aluminum. Use relatively high levels of phosphorus in the fertilizer program. Phosphorus antagonizes aluminum uptake and helps assure pink flowers. Rotating mono-ammonium phosphate (11-53-00) into the feed program will help raise phosphorus levels and help prevent aluminum uptake. An example feed program would be continuous feeding using 150 ppm nitrogen from 20-10-20 (10 oz/100 gal) rotated with 100 ppm nitrogen from 11-53-00 (18 oz/100 gal) every third feeding.

Try to maintain a substrate solution pH of 6.0 to 6.2; aluminum becomes more available at lower pH's. Be careful not to allow the pH to rise much above 6.4, or iron deficiency chlorosis will become a problem. Supply low to moderate levels of potassium. High levels of potassium tend to increase bluing of hydrangeas.

Blue Flowers Although dormant plants purchased as blues will have received aluminum sulfate prior to shipment, aluminum must also be supplied during the forcing period. Start drenching with aluminum sulfate immediately after transplanting. Apply 8 fl oz of drench per 6 inch pot using 10 lb aluminum sulfate per 100 gallons of water. Drenches should be applied to moist substrates only as drenching dry soil will result in damaged roots. Make applications at 10 to 14 day intervals. About 10 days after each application, measure the pH of the substrate. If the pH is higher than 5.6, another application of aluminum sulfate should be made. Continue this procedure throughout forcing. The aluminum sulfate not only supplies aluminum, it also maintains a low (5.2 to 5.5) pH in the substrate solution, desirable during forcing of blue hydrangeas. Use a phosphorus-free substrate for transplanting and use a fertilizer lacking phosphorus. Apply high levels of potassium for increased bluing. For example, apply 150 -200 ppm 21-0-0 nitrogen and 300 - 350  ppm 13-0-44 potassium at each irrigation.

Terminate fertilizer when flower buds begin to show color to increase the postharvest life of the flowers.

For more information

Commercial Hydrangea Forcing (PDF)by Douglas A. Bailey, North Carolina State University.

FloriCAST (short video) on fertilizing florist hydrangeas by Kimberly Williams, Kansas State University

Tina Smith, University of Massachusetts

An injector setting of 1:100 means that 1 gallon of fertilizer concentrate makes 100 gallons of final solution. It does not mean that the injector is delivering 100 parts per million (ppm) nitrogen. Many injectors have a dual settings, in percent and ratio. A 1 percent setting is the same as a 1:100 ratio, a 2 percent setting is the same as a 1:50 ratio and a 0.5 percent setting is the same as a 1:200 ratio. To make the appropriate concentrate for a specific injector setting, determine the amount of fertilizer to dissolve per gallon of water. This can be done by using a chart or calculating it yourself.  Note that fertilizer should be measured by weight for mixing, not volume. Also, fertilizer solution color is not a reliable gauge for fertilizer concentration.

For an easy to use table on injector ratios, ppm Nitrogen and fertilizer calculations see: Injector Ratio Table (PDF)

To learn more about how to calculate fertilizer ppm for greenhouse crops see: Fertilizer Calculation Fact Sheet

Fertilizer injectors should be checked periodically to be sure they are operating accurately.  This can be done by testing the electrical conductivity (EC) of the fertilizer solution. To check a fertilizer solution, use a good conductivity meter or send a sample to your State University soil test laboratory.

Procedure to check the EC of a fertilizer solution:

1. Let plain water (no fertilizer) run a little, then collect water in a clean bucket. Take a sample of the plain water from the bucket. Check the EC of the untreated water supply.
2. Mix up your fertilizer as you normally do and run it through the injector and hose. Let it run a little to be sure you get an accurate sample. Take a sample of the fertilizer-injected water from the end of the hose and use your meter or soil test laboratory to check the EC of the sample.
3. Subract the EC value of the untreated water from the EC value of the fertilizer water.
4. Compare the results to an EC chart from the fertilizer manufacturer or fertilizer bag. The chart will correlate the EC measurement with the ppm Nitrogen so you can determine if your injector and mixing procedure is accurate.

Soil Testing Laboratories

University of Massachusetts Soil and Tissue Testing Laboratory University of Connecticut Soil Nutrient Analysis Laboratory

Tina Smith, University of Massachusetts

It is time to prepare perennial plants for overwintering. Top growth has died back on many perennials while on others, it will remain over the winter. Prepare plants for overwintering by cutting back dead growth and removing dying debris to prevent Botrytis infection.

Next, irrigate if needed, but allow any foliage to dry prior to covering to prevent Botrytis. Check soil moisture periodically and water if needed, but avoid over-watering plants throughout the winter. If plants are kept too wet, root rot diseases will occur.

The final step prior to covering plants is to provide some type of rodent control. Many growers use commercially available baits while others have reported that human hair or cut up deodorant soap works.

Soil temperatures should be in a range of 30 to 34º F for most perennials. Soil temperatures that are cooler than 30º F may kill some sensitive species. Use a soil thermometer to verify that growing media are in this range.

The key to overwintering containerized perennials is to avoid wide fluctuations in temperature. When plants are allowed to freeze and then thaw, there is a greater risk for plant loss.

There are two basic concepts growers use to overwinter perennials. Plants are either maintained below freezing or above freezing temperatures.

Heated greenhouses with roll-up sides are one option that works well for many growers. To use this method, perennial houses are heated to 50°F until all of the plants are well rooted, then the temperature is slowly decreased to 35°F so the plants will vernalize and flower in the spring. The roll-up sides are useful in the spring to regulate temperature and prevent plants from growing too quickly. Massachusetts has six hardiness zones representing a wide range of temperatures. As a result, growers here use many different methods for overwintering herbaceous perennials in containers ranging from grouping plants and covering them with overwintering fabric to using heated greenhouses.To learn about various methods see the following fact sheets:

Overwintering Containerized Perennials Preventing Rodent Damage to Overwintering Perennials

Leonard Perry, University of Vermont, has some good information and an on-line slide show on overwintering perennials based on his research. Perry's Perennial Pages

Tina Smith, University of Massachusetts

Rich McAvoy, University of Connecticut provided a good article on scheduling the 2009 Easter Lily crop. Below is a little information from the article. To see the entire article including energy saving options for growing Easter Lilies see: High Oil, Tough Choices - Scheduling The 2009 Easter Lily Crop. Tina Smith, University of Massachusetts

With record high energy prices lily growers will be looking for ways to reduce oil consumption or cut production costs. Tighter crop spacing, increased double cropping and lower forcing temperatures are the steps most growers resort to first. Last year some growers added an extra layer of plastic film, suspended above the truss, to provide some extra insulation. Any reduction in light, from overhead structures or baskets, will affect lily development. Every time you add an extra layer of plastic film, you reduce light transmission by as much as 10%. If the film collects condensation and dust, light transmission is further reduced, and of course more overhead baskets reduce light even more.  Easter lilies are a high light crop. The best quality lilies grow under maximum light conditions. As light is reduced, stem stretch and the incidence of lower leaf yellowing increases. If increased overhead shading is combined with tighter spacing, the incidence of stem stretch and leaf yellowing will increase even more.

In 2009 Easter falls on April 12, this is mid-date Easter that will allow plenty of time for forcing (see the 2009 Easter lily schedule (PDF) for details).  This is good news since you can grow cool for most of the schedule and still bring the crop in on time.

The normal Easter lily schedule for pot-cooled bulbs takes a total of 23 weeks. This includes 3-weeks in the pot at 60-62°F to stimulate root development, 6-weeks of bulb cooling at 40-45°F and then 14-weeks of greenhouse forcing at 60-65°F or higher as needed. For case-cooled bulbs the process is still 23 weeks but this includes 6-weeks bulb cooling at 40-45°F and then 17-weeks of greenhouse forcing.

This season start bulb programming by November 2 (23 weeks before Easter).  However, bulb programming must begin as soon as bulbs arrive and they may arrive early (24-25 weeks before Easter).

Many growers (who are growing their garden mums in outdoor fields) may have a few greenhouses empty between crops. If so, it's a good time to do a thorough clean up, including removing existing weeds (either hand pulling isolated weeds) or using a post emergence herbicide such as glyphosate that can be used in an empty greenhouse between crops as well as outside greenhouses.  However, both of these measures do not prevent reseeding of weeds. So, repair any tears in the weed block fabric or replace if needed. 

For more information see: Managing Weeds In and Around Greenhouses

Leanne Pundt University of Connecticut

Many growers will be potting up garden mums and it's a good time to revisit your fertilizer program. Mums are heavy feeders during the first few weeks. After flowers are formed, nutrient demand diminishes. Your fertilizer program and fertilizer selection should be based on irrigation water quality, so have your irrigation water tested if it hasn't been done and conduct regular soil tests to monitor soil fertility.

There are several ways to fertilize mums. Some growers use 100% water soluble fertilizer through a drip system, some use 100% controlled-release fertilizer and some use a combination of water soluble and controlled-release. To start plants off right and prevent premature buds:

Use moistened soil when potting up plants, then water-in freshly planted cuttings with a fertilizer solution containing 200 to 300 ppm of 20-20-20 immediately after planting. The cuttings will establish faster and grow more rapidly.

Do not stress the young plants during their first 4 to 5 weeks of growth, especially during the first 10 days of the crop. Keep plants moist, well fertilized and properly spaced.

Check plant roots regularly to monitor plant health.

To encourage soft growth that branches freely, use 250-300 ppm 20-20-20 or a fertilizer that is at least 60% ammonical nitrogen as a constant feed during the first 2-3 weeks for all fertilizer programs. If using controlled-release fertilizer, keep in mind that its rate of release is affected by its formulation (rate of release), soil temperature and frequency of irrigation. Most formulations release at temperatures of 70°F or above, therefore during cold temperatures of late spring/early summer temperatures, fertilizer is going to be slow to release, when plants need the most fertilizer. This is why liquid feedings become important, to get plants moving and create vegetative growth. Liquid feeds of at least 60% ammonia forms of nitrogen, combined with no water stress, are important to minimize premature budding!

Examples of Fertilizer Programs for Garden Mums

100% Water Soluble Fertilizer Using Drip Irrigation After plants are established using 20-20-20 the first few weeks, switch to 200-250 ppm of 20-10-20 constant feed for 3-4 applications and then rotate to a calcium nitrate based fertilizer such as 15-0-15 for 1 application, then repeat. Once plants start to show color, reduce to 100 ppm constant feed.

Combination of Water Soluble Fertilizer and Low Rate of Controlled Release Fertilizer Use 250 ppm of 20-20-20 at time of planting and constant feed for first two weeks  then change to 20-10-20, 300 ppm once per week and use clear water from first color until sale.

More information is available from:

Yoder 

Garden Mums from Cell Packs (PDF)

Tina Smith, University of Massachusetts

Whether spring plants are being moved outdoors to free up greenhouse space or displayed in outdoor retail yards, there are a few precautions to take at this time of year when temperatures can quickly dip from 80° to 25°.

Begin by choosing cool tolerant plants such as pansies, osteospermum, snapdragon, argyranthemum, petunias, verbena, bidens, calibrachoa, diascia, nemesia, annual phlox, alyssum and lobelia. Tropical and subtropical warm crops such as alternanthera, angelonia, New Guinea impatiens, lantana, vinca, celosia, cleome, coleus, cosmos, gomphrena, ipomoea, melampodium, portulaca, sunflowers, zinnias and many vegetables are naturally sensitive to cool temperatures and are not a good choice for early spring outdoor yards.

All plants, subjected to cold temperatures, should be acclimated or hardened off first. If taken directly from a warm greenhouse and not hardened off, even perennials and cool tolerant annuals will be injured by low temperatures.

To acclimate plants, lower the greenhouse temperatures to 45° – 55°F for several days or move plants to a cold frame for added protection. Monitor the weather forecast. As a guideline, avoid moving plants outdoors if a hard frost (colder than 28°F) is predicted at any point within at least three nights of when plants would be put outside and avoid moving plants on windy days. Use a minimum recording thermometers to monitor outdoor yards.

During mild weather, move the plants outdoors, and provide adequate space for good air movement. Avoid placing plants in low-lying areas where frost will more likely settle. Cold, dense air flows by gravity to the lowest areas where it collects.

Be prepared to cover plants with over-wintering thermo blanket such as polyethylene or polypropylene foam or move plants indoors if temperatures are expected to go below 28°F.

Without some sort of protection, you are always taking a chance when growing outdoors in early spring and occasionally plants will get damaged. By choosing cool tolerant plants, acclimating plants, closely watching weather forecasts and providing extra protection when needed, you can minimize risk, grow higher quality plants and provide an extra turn in production.

Tina Smith, University of Massachusetts

For more information see:

Moving Cool Tolerant Plants Outdoors: Risks and Benefits

Seasonal Outdoor Growing (by Four Star Greenhouse, Carleton, Michigan)

Root rots, foliar diseases and under-fed plants from over-watering and tall leggy growth from low light are common problems that occur during prolonged cloudy, rainy weather.

During prolonged cloudy, rainy weather, let plants run on the dry side and spot water areas as needed to prevent over-watering. Usually plants on the edges of benches or those in the path of air movement will dry first and may need to be spot watered more often than the rest of the crop. When some plants get spot watered and are irrigated more frequently than the general crop, their fertilizer program needs to be adjusted to account for the extra leaching they receive. They may need to be "spot fertilized" as well.

If media remains wet, plants are more prone to root rot. At least once a week, randomly select plants to inspect roots to monitor the health of the crop. If roots do not look healthy, conduct a soil test for soluble salts and test roots for disease, either by sending samples to a lab or by using on-site test kits.

To prevent foliar diseases like Botryis, (see message) always water in the morning to reduce the length of time the leaves stay wet after irrigating. Avoid watering late in the day or when water will sit on leaf surfaces for long periods of time. Reduce humidity by heating and venting several times in the evening and in the morning. For details, see the factsheet, Reducing Humidity in the Greenhouse. In addition to heating and venting, use circulating fans (horizontal air flow) to continuously move the air throughout the greenhouse. These fans should be shut off when exhaust or vents are being used. Horizontal air flow will mix cool and warm air, minimizing temperature differentials and cold spots where condensation can occur on plant surfaces. For more information see: Horizontal Air Flow

If pesticides are needed, read precautions for treatments during prolonged cloudy weather. Some products such as horticulture oil may cause phytotoxicity if it remains wet on the foliage and does not dry rapidly.

High temperatures and low light conditions increase stem elongation or stretch. Water soluble plant growth regulators such as B-Nine and Cycocel are best applied during cloudy weather to maximize chemical uptake. With transplants in small containers (flats & 4" pots) materials such as B-Nine and Cycocel can be sprayed at weekly intervals. Apply the first spray as soon as new growth is evident. Use a rate at the low end of the recommended range for that species. Repeat at 7-14 day intervals as needed. For more information on using plant growth regulators see articles from March and April 2007 on Plant Growth Regulators. (Articles from search are displayed in reverse chronological order.)

Tina Smith, University of Massachusetts with input from Leanne Pundt, University of Connecticut

How a mix is handled can affect the air and water content of the mix. Compaction is an important factor to consider for plant root health when handling growing media. Air space that results in good drainage can be cut in half or even eliminated by compaction. To minimize compaction, containers, cell packs and plug trays should be lightly filled and the excess brushed away. The media should not be packed down, tamped down, or the filled pots tapped down on the bench several times, and the pots and trays should not be stacked directly over one another.

Another consideration is the moisture content of the mix prior filling containers. When water is added to dry components such as peat, they hydrate and swell. This swelling helps to create more aeration by preventing the particles from nesting within one another. This is especially important in plug production. Water should be added to the mix before it is placed into the container. It is best to moisten, then mix and then allowed to set overnight prior to use. If that is not possible, waiting at least a couple of hours after adding the water will help the hydration process.

How much water to add to the mix? For peat-based mixes for large containers and bedding plant cell pak production use 1 water:1 dry substrate ratio (50% moisture content). Plug mixes should have 2 water:1 dry substrate ratio (67% moisture content). The rule of thumb is, the smaller the cell, the more water to add prior to planting.

For more information see: "Greenhouse Substrates and Fertilization (PDF)", by Douglas A. Bailey, William C. Fonteno, and Paul V. Nelson Dept. of Horticultural Science, NCSU

Tina Smith, University of Massachusetts

Pre-Season Cleanup

Hopefully, your greenhouses are now thoroughly cleaned so there is no leftover debris, organic material, weeds and "pet plants" that may serve as a source of pests and diseases plus thoroughly disinfested in preparation for the upcoming growing season.

Inspecting incoming plants

Inspect incoming plants for key insects, diseases, weeds and cultural problems. Inspect the entire plant  - leaves, stems and roots for signs of pest activity and for general health. Roots should be white with vigorous growth - brown, decayed roots are evidence of root rot disease or root death due to other causes such as overwatering or high salt levels. If at all possible, do not accept plant shipments with serious insects or diseases with wide host ranges, and are difficult to treat. For example, incoming plants may be infested with resistant insects, mites or Botrytis spores that will be more difficult to treat. Do not accept plant material infected with incurable diseases, such as viruses, bacterial leaf spot diseases, or foliar nematodes. If you need confirmation, isolate a few plants showing symptoms and send them to a diagnostic laboratory. If you find isolated evidence of some insect activity, for example, aphids, and decide to keep the shipment, identify an isolated, quarantine area in which to keep the plants. Treat immediately and hold the plants in this area until you are sure that they are healthy, salable and free of pest problems. Ask workers to enter this quarantine area at the end of the day to avoid moving pest problems throughout your operation.

For more information:

Cleaning and Disinfecting the Greenhouse

IPM Scouting and Decision Making

Leanne Pundt Extension Educator University of Connecticut

A frequently asked question (FAQ) is "Can I use unvented heaters in the greenhouse, either for back-up or as a primary heat source?

An unvented heater is one that is designed without a flue connection so that the heat and products of combustion are exhausted into the greenhouse. Dumping these flue gases into the greenhouse may improve the overall efficiency rating as compared to a conventional heater but the pollutants and added moisture from combustion may put your plants in jeopardy.

Unvented heaters can be fired with natural gas, propane or kerosene. These fuels are advertised as clean-burning. This is generally true if the burner is clean and has been adjusted to top efficiency. A heater that has been serviced in the fall will probably not be at peak efficiency as spring approaches. Inefficient combustion can emit unwanted and harmful pollutants into the greenhouse that can affect the plants and the people working with them.

Care should taken if you install unvented heaters. Be sure to have an adequate makeup air supply and provide frequent maintenance. Use indicator plants near heaters or commercially available indicator tubes to warn of excess levels of pollutants.

For more information about the fuels, the combustion process and their pollutants see the fact sheet:

Problems With Using Unvented Greenhouse Heaters

John Bartok, Extension Professor Emeritus, UConn

Pesticide phytotoxicity can often be distinguished from pest problems by the pattern and timing of symptom development. Although the damage may take up to several days or more to occur, pesticide damage symptoms often occur all at once and often have a regular distribution on the crop. Symptoms caused by pathogens usually develop over an extended period of time in random or grouped patterns. Pesticide phytotoxicity can be expressed by a number of different symptoms, including leaf speckling, cupping and twisting and other leaf distortions or even plant death. Pesticides with hormone-type activity such as the insect growth regulator Distance and herbicides containing 2,4-D tend to produce leaf cupping and twisting. Other pesticides that have caused twisted growth include Judo applied to dracaena plugs and Botanigard ES applied to tomato plants.

Phytotoxicity can also be caused by the solvents in a formulation (EC formulation vs WP), impurities in spray water, using a higher rate of pesticide than is listed on the label, tank-mixing or inadequately mixing the spray solution. Environmental conditions such the temperature, humidity, and light can also influence phytotoxicity. High temperatures can speed up pesticide degradation and volatilization, but may also result in increased phytotoxicity for some products. Plants that are stressed are more susceptible to pesticide injury.

At this time of year, poinsettias will become more sensitive to spray injury as bracts turn color. Pesticide applications to poinsettia bracts are risky since there are so many variables. Differences in cultivars, culture and environmental conditions may increase or decrease bract sensitivity to pesticides. If you are inexperienced with a particular pesticide, always test a small portion of your crop before treating your entire crop.

To prevent injury due to pesticides, be sure to follow label directions exactly. See the company's website to read any technical bulletins about the product or call the company's technical representative before using a product for the first time.

If minor phytotoxicity is suspected from foliar applications of an insecticide, miticide or fungicide, watch the new growth as it emerges. Plants will often grow out of one-time spray damage. As plants grow, the damage will remain on the oldest leaves and the new growth will appear healthy.

Articles: Dilemma of Tank-mixing by Raymond Cloyd Whiteflies on Poinsettias - Late Season Control

Photos of Pesticide Phytotoxicity: Judo injury on dracaena plugs and ivy geraniums (See technical bulletin for list of crops for which Judo should not be used) Distance injury on poinsettia BotaniGard injury on tomato plants 2 Herbicide injury on tomato and geranium

Tina Smith, University of Massachusetts