Tips for Heat Stress in the Garden by Vicky Spelman

Heat stress in cucurbita moschata
Photo:  iStock

Whew... it is hot in our area (Denver Metro).  Are you seeing heat stress in your plants?  Different plants can have different reactions.  Here are a few signs to look for and some tips to manage it. 

• Most plants will grow best in temperatures that range from 59º to 86ºF. When temperatures are consistently above 90ºF for long periods, plant growth is slowed down.  Some may start to show signs of stress.  

• Many plants will survive temperatures above 104ºF – but the type of plant, drought and wind will be factors of how the plant manages heat stress.

Signs of heat stress:  Leaf rolling and cupping, wilting, dry leaf edges, blossom and fruit drop, bolting, sunscald (blossom end rot can become more of a problem when sunscald is present).  

Bleached area on fruit surface is caused by sunburn
Photo: Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org

Sunscald on leaf
Photo:  Daren Mueller, Iowa State University, Bugwood.org

Some things you can do:

• Mulching will help conserve moisture

• Consider using a shade cloth (or other ways to shade)

• Moving containers to a shady area

• Weeding to reduce water competition 

• Waiting to plant or transplant until cooler temperatures arrive

• Waiting to prune trees and shrubs

• Waiting for cooler temperatures/period to fertilize

This was condensed from an excellent article (and more photos) by Oregon State University: https://extension.oregonstate.edu/gardening/flowers-shrubs-trees/heat-wave-garden-how-identify-prevent-heat-stress-plants?