August 22, 2021
Our June heat wave hit just after the summer solstice, precisely when the days are the longest of the year. Double whammy! Record high temperatures in June beat our plants to the max. Ouch! We all witnessed the most obvious punishment, sun scald.
What’s a plant to do? The stomata pores of plant leaves open to welcome carbon dioxide, the start of photosynthesis. At the same time, when those pores are open, water vapor exits the plant (leaf transpiration). When it’s hot, dry and breezy, that loss of water can be deadly for the plant.
During the three-day period June 26-28, 2021, daytime high temperature averaged 102.5F (normal is 71), daytime low humidity was 26% (normal is 50), and average wind speed was 5.6 mph (normal is 3.3).
The plants strategized by opening those stomatal pores during the cooler mornings, and then button up in the afternoon!
What’s a gardener to do? I am sure you watered like mad. I chose to drape my veggies with shade cloth, to reduce temperature and, to some extent, reduce wind. If plants could walk, I think they would hightail it to shade during those June afternoons.
Well, here we are in August. Due to zero precipitation and additional periods of high temperatures, the soil around all our garden beds and tree guilds is dry. I looked at 2019 and 2020 August photos of the orchard; some green grass is evident. Today I noted, brown, brown, brown, except for plants with long tap roots. In fact, you can slide on the grass!
This lingering hot dry situation this summer brings us back to leaf transpiration and plant water loss. Water has to move up from the soil, to the root hairs, and up the xylem (tiny vertical pipe) to get to the leaf. Leaf transpiration is the main force that pulls the water up this path.
So, what’s a gardener to do now? Remember 2015 when we had a drought? Many City trees died, but not until 2016. Prepare for next year!
Now is the time to take good care of your perennial plants, especially those that are still forming fruit. Ideas are extra watering, providing shade, and heavy mulching. You might also avoid heavy pruning.
Come Take a tour of the orchard to see all the different water conservation techniques we use.
Water Plant and Soil Relation under Stress Situations
Filipović , Adrijana
September 16th 2020
Transport of Water and Solutes in Plants
Botany Professor blog, Water Potential Explained, 05/07/2015
From mountain forests to city parks, trees are stressed and dying
Mapes , Lynda V. August 6, 2016 Seattle Times
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