Bottoms-up watering may revive heat stressed plants (Seattletimes)

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Bottoms-up watering may revive heat stressed plants

Yard Smart: Horticulturist Maureen Gilmer offers tips on how to get water to the roots of container plants.

By MAUREEN GILMER

Scripps Howard News Service

In August, the once beautifully potted plants sit listlessly on porches, patios, balconies and roof gardens. Greens, herbs, flowers and perennials all seem to give up on life this time of year no matter what we do.

Nine times out of 10, the cause is simply dry roots. Note: I have not said “lack of water” because even in the summertime, plants get watered plenty. The problem is that the water doesn’t go to where it’s needed in the plants.

Look closely at your potted plants to see how the soil shrinks when it begins to dry out. This leaves a gap between the edges of the soil and the pot wall. The water that you apply seeps through that gap and out through the bottom. How much of the water do you actually think gets absorbed into the potting soil or roots?

Slide the plant out of the pot and you will find that the roots are concentrated in a thin but dense layer around the outside of the soil mass known as the root ball. The roots have created this mass around the soil because that’s the only place water can be found, however briefly that may be. This may have been fine in the cool days of late spring, but come late summer with the heat, it’s simply not enough moisture to maintain healthy, beautiful plants.

The best way to revive these plants is to encourage them with a payoff of moisture deep within the dry root ball. Once accomplished, the roots will moisten and grow, where it is dark, cool and wet. So how do you get the root ball thoroughly moistened?

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Published by

Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.