Heat Delay
When exposed to prolonged periods of excessively hot summer temperatures, some pot mums may fail to flower on their projected flower date. This delay in flowering is termed heat delay. Other symptoms of heat delay or heat stress may be expressed through the development of bract tissue in flowers or malformed flowers.
Several steps can be taken to minimize heat delay in pot mums:
- First and foremost is the selection and use of heat-tolerant varieties. (Consult variety listings in this brochure, the Yoder Pot Mum Variety Guide or your local sales representative.)
- Reduce air and plant temperatures as much as possible once short days begin and until bud color is visible.
- Light intensity should not be reduced below 5,000 to 6,000 footcandles or plant quality may suffer.
- If possible, ventilate underneath and through the black cloth.
- Pull the black cloth as late in the day or evening as possible to allow excess heat to ventilate from the greenhouse.
- Extend the black cloth application from 12 hours upwards to 15 hours per day. Example: Pull black cloth at 7 p.m. and uncover at 10 a.m.
- Open the black cloth for ventilation after night falls and close again before sunrise if automatic systems are available.