Why does my zucchini plants wilt in the sun?

Question

The instructions state to plant zucchini in full sun, but my plants wilt in the heat. Also, can anyone tell me why the leaves on some of the plants turn grey? I live in Northridge, Ca where it does reach temps in the 100's.

Answer 1

You are not watering enough.  Water every day and do NOT use a sprinkler.  You will burn the leaves.  Use a soaker.

Answer 2

They are too hot.  That is the plants way of protecting itself from the sun/heat.  Make sure that you give them plenty of water.  Don't water them during the day as water on the leaves will cause burns.  The gray is powdery mildew.  It usually doesn't hurt the plants, especially late in the season.  

Answer 3

The 100 degree heat is a little excessive but what can you do. The large leaf structure dictates that it is a water hog. water may not actually stop the wilting in the heat that you endure. it is kinda natural that big leaf plants will wilt during the heat of the day - no real worries. water as they require - not necessarily to stop the wilting. If they are still wilted in the cool of the morning than they are drying out - so water.

The grey leaves is a fungus. Kinda like powdery mildew that is common on Crape Myrtles. It is caused by the leaves staying wet for long periods ( overnight ) or high humidity. To prevent this as much as one can water only the grnd ( not overhead) and in the morning so it will dry the leaves in the heat of the day.

You may be watering to much to stop the wilting and hence have started the " fungus " , grey leaves you have now.

Answer 4

Wilting occurs when the roots cannot take send up enough water fast enough to keep the leaves turgid.   Bright sunny and windy, high heat all contribute to wilting. Also damage to the stem from bruising or borer damage ,   If they are only wilted in the heat of the day and perk back up when it cools off at night, this is normal.  

Agreed, the "greyness" is likely to be powdery mildew.   This occurs when the humidity is high or if you are getting the leaves wet in the evening with your watering program.  wet dark conditions encourage this condition.