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Understanding Water vs. Plant Behavior

“I have to water my plants — they’re drooping!” Oh, how I wish I had a dime for every time I heard that… You might find me in Provence nibbling cheese and sipping wine.

The truth of the matter is all plants droop in the afternoon, regardless of the moisture in the soil. During hot months, the process of moving water from the soil and roots to the leaves – known as evapotranspiration – simply cannot keep up late in the day and so the leaves droop. This does not mean the plant will die, and it certainly does not mean you have to water!

Years ago, I visited a well-meaning and very water-conscious homeowner who wondered why her periwinkles were always dying. She watered them every day at 5:30 p.m., when they started to droop. Unaware that certain varieties of periwinkles will grow in between cracks of concrete, she was killing hers with kind ignorance.

Whether they’re begonias, roses, pentas, daisies, geraniums or even impatiens, if they’re planted in the ground, you will kill or severely damage them if you water every day.

The general rule is to water deeply and infrequently for all plants, whether grass or trees. This may mean once a week or once a month. If a plant is severely wilted in the early morning between regularly scheduled irrigation, it requires either additional irrigation or the soil is so wet that the plant’s roots are rotted.

Remember that native and adapted plants may require water two to three times a month in the absence of rain. Container grown plants may need it two to three times a week. In both cases, over-watering kills. Check the soil or container with the best moisture meter in the world: your finger.

Mark Peterson
Mark Peterson
Mark A. Peterson is a conservation project coordinator for San Antonio Water System. With over 30 years of experience as an urban forester and arborist, Mark is probably the only person you know who actually prunes trees for fun. When not expounding on the benefits of trees and limited lawns, you’re likely to find him hiking San Antonio’s wilderness parks or expounding on the virtues of geography and history to his friends.
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