How Hot Is Too Hot For Plants

Caring for plants during a heat wave.

Tips

1. Before extreme heat arrives
   • Water deeply during the cool part of the day to hydrate plants.
   • Spray leaves in early morning to remove pests and dust. The leaves will dry off quickly as the day proceeds, reducing the chance of excessive fungal and bacterial growth.
   • Trim young, tender growth if you think the plant will have trouble maintaining hydration.
2. It is so hot out there!
   • • Shield young plants with screen, shade cloth, or white sheet.
     • If your plant is stressed, check the soil to make sure it is dry and then water deeply. If soil is moist, more water will not help. Most plants shut down during extreme heat, so if it is over 100 degrees, it may be best to wait to water even if your plant is stressed. 
     • Mist leaves with a spray nozzle to cool down plant and reduce transpiration.
3. Post Apocalypse
   • Once it has cooled down, water plants deeply.
   • Do not remove wilted leaves just yet. They will serve as sun shield if another heat wave is on the way.
   • If plants that exhibit summer dormancy have lost most or all of their leaves, allow them to continue into dormancy by not watering. Extra water now could pull them out of dormancy. These stressed plants may then expend a lot of energy growing a new set of leaves only to be faced with the likelihood of more heat and no natural rainfall. If they do not emerge from dormancy, they will be susceptible to fungal pathogens that grow in moist, hot soil.