Production areas with black fiber cloth were hot, hot, hot this week. Garden mums, flowering cabbage and kale may exhibit signs of wilting during extended periods of 90 plus degree temperatures. The solution may not be as easy as turning on the irrigation. Plants 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 the plants will show signs of stress by wilting.
Garden 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.
Signs of poor root health are blackened or rotted roots or lack of roots. Diseased roots will not take up fertilizer.
Tina Smith, UMass Extension