Question of the Week – Number 1 May 20, 2021 – Wilted, but Wet

Oakleaf hydrangea is wilting after just 30 minutes of exposure to sunlight, even though it’s just been through a week’s worth of rain.

“Why are my oakleaf hydrangea and tomato plants wilted, even though it’s been raining and their soil is wet?

At first pass, this seems highly improbable. But when I explain why it happens it will make all the sense.

1. These plants use a great deal of water to sustain all their verdant new growth in the spring.

2. When they encounter several days of cool, cloudy weather, and especially when rain is involved, that growth becomes what horticulturists call “soft,” or succulent.

3. When the sun comes out and hits that tender new growth, it’s like human flesh that’s exposed to intense sunlight for the first time in the spring – the leaves overheat quickly. They call for more water as a means of keeping their cells fully hydrated.

4. When they can’t pump the water through quickly enough, the plant tissues wilt.

5. Usually this all passes once the plant moves into shade or when nighttime arrives. Generally it’s not as pronounced after another day or two.

Continued Below

Those who live in areas that have seen consecutive days of cool, cloudy weather this week are likely to see this happening to large- and floppy-leafed plants in the next several days.

Don’t despair. And, whatever you do, don’t water them if their soil is already wet!

Note: Plants that have been consistently too wet because of poor drainage may also be wilted. The difference will be that they won’t recover overnight. The way you can tell if it’s poor drainage is to dig a 12-inch-deep “post hole” beside an affected plant and see if it fills with water oozing out of the soil within 12 to 18 hours. That will tell you that the water table is near the soil surface, and that the water is crowding oxygen out of the root zone.

Posted by Neil Sperry
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