Heat

Normally, when the daily mean temperature is higher than 35℃, many plants would suffer ill effects. There are some signs that you could use to identify whether plant is under heat stress. Some of these signs are as follows:

• • Wilting: This is the same as drought stress, the heat stress also causes the plant to wilt. The main difference between heat wilting and drought wilting is that in heat wilting regardless how much moisture in the soil, the plant still wilts.

  • Leaf dropping. Some plants will drop significant numbers of leaves when they are exposed to heat stress.

  • Stop flowering and fruiting. Some plants may stop flowering in hot weather, many Solanaceae family plants such as tomato and sweet pepper fall into this category. They may drop their flower without developing fruit or may not flower until the weather gets cooler.

  • Bolting. Instead of non-flowering, cool weather vegetables like broccoli, cabbage and spinach may start to flower when the weather becomes too hot. The heat signals the end of their life span and culminate in flowering and seed production. There’s not much you could do to stop the bolting, the only thing you could do is to harvest and use the plants before the flavor is ruined by the bolting process.

  • Blossom end rot. Tomato, pepper, cucumber and squash may exhibit black spots on their bottom in hot weather. The end rot disease is caused by calcium deficiency. Since the calcium deficiency is often caused by inconsistent soil moisture, the high temperature and drought plays an important role in this disease.

  • Sunburn. This usually happens to newly transplanted plants when they get sudden sun and heat exposure which is more intense than they used to in the nursery house. The leave tips would become dry and brown because of the heat.