Stressing Out In This Heat?

Grape vine leaves sunburned on the surfaces that were angled perfectly to get too-intense sun rays.

Burned edges.

Burned individual leaves.

Sunscalded Silver Dollar plant rootings.

Succulent leaves "melted" in the heat.

At least 2 branches are still green. Don't prune back anything until you see what's really dead in a month or two when new growth emerges. You'll probably be surprised at how much original foliage is still viable.

Fig tree sprouting new growth after all of its original foliage "fried" and drooped. I soaked the entire rootball when I found the container on its side and thoroughly dried out.

The beans are still happy. We'll see if they hold onto their blossoms to set the fruit.

Purple People Eater Angel Trumpet loves the heat, but it's protected from the late afternoon blasting sun.

     Hot weather has finally arrived, and plants as well as people are suffering.  Neither of us had a chance to acclimate, so we’re all feeling the brunt of the heat.  While mid-80 degree temperatures may feel slightly warm but still comfortable to people, vegetables like tomatoes and peppers and eggplants (they’re in the same family) can’t complete the pollination process then.  And, in the low-90s, beans stop producing blossoms altogether. 
 
How do I know that my plants are having a hard time during the heatspell? 

• Plant growth slows because chemical activity slows during high air and soil temperatures.
• Foliage may droop and look dull instead of glossy, especially early in the morning which indicates that they haven’t recuperated overnight. 
• Leaves may roll and cup to reduce the amount of evaporation and direct sunlight.
• Leaf edges may dry
• Foliage may be sunscalded on the side of the fruit most exposed to the sun, looking like dead and discolored blotches.
• Plants stop flowering.
• Plants drop buds and flowers, especially after an extended period of high temperatures, and on peppers, squash and cucumbers. Production will resume after the heat wave is over.

 
Watering in the early evening

• Water deeply as soon as possible to keep plant entire root zones thoroughly hydrated.
• Sprinkle foliage after the sun no longer is directly shining on the plants, both on the undersides as well as on the tops of the foliage.  Evening is when the stomates on the undersides of the leaves open up, allowing more absorption of moisture.  Even though air temperatures are still high, evening breezes will help dry the water on the foliage so that diseases don’t become a problem since you’re doing this only the once to recuperate the plant.  

    
Shading
Protecting plants from the intense heat in the late afternoon can be accomplished several ways.

• Shade cloth or cheesecloth covering the tops of the plants, or on the south and west sides will lessen the effect of the direct sun.  The material must be porous, however, to enable sufficient air circulation for the merest breeze to help move the hot air.  Old window screens or nursery trays allow air to pass through them.
• Fencing or other sturdy item with sheeting can be placed to the south and west sides of the plant to block the direct sun during that late-afternoon period.  Keep it away from touching the plant, however, so that it doesn’t block any breezes. 

 
Mulch

• Add more mulch on top of soil surfaces that have been well watered.  You want to insulate moist soil so roots can be further cooled and protected.  Mulch reduces temperature changes and evaporation.

 
If the heat spell continues

• Keep the soil moist but not wet throughout the entire root zone so that both moisture and air will always be sufficiently available when the plant roots need them.
• Keep shading devices installed.
• Don’t plant or transplant.  These activities are stressful enough for plants, without the additional heat stress issues.
• Don’t apply any chemicals for plant disease and insect issues, even soap or neem oil, when air temperatures are above 80 degrees.
• Do get rid of weeds, many of which do well during temperature extremes  and certainly do compete with garden plants for water and nutrients.

 
After the heat spell retreats

• Don’t prune or fertilize, as these activities stress the plant even more.
• Instead, allow plants to rebalance themselves in relief from the intense heat for several weeks.
• After a month or so, when you see that new growth has emerged and perhaps blossoming has resumed (once the air temperature is again consistently below about 85 degrees), then you can gently trim dead foliage without fear that you’ll stress the plant even more.
• Resume planting and transplanting.

 
For garden tasks, see August.
 
For other major-topic blogs for this time of year, see Homepage.