Chrysanthemums - Early flowering and short plants
Tuesday, 04 August 2009 11:39
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
