Monday, June 22, 2015

Water Stress in Plants

Wilting, browning of the tips of leaves, yellowing leaves, these symptoms are all signs of water stress. Water stress comes in two forms which can easily be mistaken for the other, drought and too much water. If you treat for the wrong one, odds are you will finish off your already stressed plant.

The first picture in this post is of a young walnut tree that I have in my backyard. At first glance would you say the browning of the leaf margins and somewhat yellowed leaves are due to drought or over watering? Often times when you notice a plant with water stress symptoms, you need to do some detective work to figure out the answer correctly.

I can tell you that I first noticed the browning tips of this tree towards the end of May, 2015 and that May, 2015 was the wettest year on record in the DFW area. I'll also let you know that while the picture of the mallards was taken in June, my backyard had more standing water in it for much of the latter half of May, including the area just north of and sometimes including where the walnut tree is planted.

By now I'm thinking that you have guessed that the browning on the leaves is due to too much water. The soils became saturated with our record rains for a prolonged period and the roots were not able to breathe properly. Luckily we did have almost two weeks without rain that allowed the soils to drain, allowing the tree to recover. You can see there is new, healthy looking darker green growth above the browned, water stressed leaves.

The moral of this post is to stop and think before your grab the watering can or hose when you see a wilted, yellowed or browning plant. Evaluate what has happened to the plant recently. Check the soil moisture a few inches down (whether in a pot or in the ground). Water if dry, otherwise do what you can to help the soil drain and dry out a bit. Some plants are more tolerant of wet feet than others. I've found live oaks to be very tolerant of standing water for prolonged periods of time, whereas desert willow needs good drainage all the time in order to thrive.

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