Using Plant Growth Regulators to Hold Finished Plants
Wednesday, 25 April 2007 11:39
Growers sometimes need to hold plants in check once they reach or approach the final size. This is especially true when weather conditions dictate that plants be held longer than anticipated. Under these circumstances, a spray or drench application of one of the more root-active compounds (A-Rest, Bonzi, Sumagic, Topflor) can do the trick. The danger here is that an overdose can have a long residual effect and if over done the plants may not perform in the garden for the consumer. For a proper hold, select a concentration in the upper half of the normal recommended range for that crop. You can even go 50% higher than the rate recommended for slowing growth during the grow-out stage. For instance, the normal spray rate for A-Rest on Ageratum in flats during grow-out is 10-15ppm, but a rate of 15-26ppm is recommended to hold this crop. The same principle would apply for the other PGR compounds. Note, I would not recommend Cycocel for this purpose since the spray rates required would be so high that phytotoxic injury would be likely to occur.
If you don't have experience with using PGRs to put a hold on growth, start with the high end of the normal recommended rate. You can always do a second treatment if the first is not enough. A proper hold rate should give enough control to hold a mature plant under hot weather for 2-3 weeks but low enough that the plant will recover and grow for the consumer. Spray treatments carry less of a risk of overdose than drench treatment, especially when the root-active PGRs are used.
Photos:
Plant Growth Regulator Overdose, 2
2011-2012 New England Floriculture Guide
Fact Sheet:
Growth Regulators for Bedding Plants
Rich McAvoy
