Saving a garden in relentless heat

As of today Tucson has suffered under daily high temperatures over 105F (44.5C) for 39 straight days. And the TV weather lady tells us these conditions will keep on going. No monsoon rain relief in sight in this part of the Sonoran desert. A friend in Las Vegas tells me it is as bad up there in the Mojave desert.

While this persistent heat is awful for humans, we can take shelter in air conditioning. Plants in the garden, however, cannot. So, what to do to help your plants survive this–or any other–extended period of heat?

The first thing that may come to mind is to increase watering the garden. Sadly, deep watering plants may or may not help. With day-after-day of temperatures of 90-100F+, some plants, particularly non-desert plants, cannot absorb water faster than it is evaporating through the plant’s leaves. Death by dehydration results.

Here, however, are 3 ways to help your plants survive until Fall.

Shade Cloth is a quick remedy

Shade cloth is a fast solution for plants that appear to be suffering from heat exhaustion. You can buy it today, hang it up over vulnerable plants or borders in your garden and the protection starts immediately even if you have to just tack it up in a temporary make-shift way. Shade cloth comes in variety of weights and with UV protection.

Double pot to cool roots

For the plants that are in pots the heat and afternoon sunlight can be especially brutal. Placing pots where they will be in shade for most of the day is a recommended, but that may not be enough. Again, the problem is death by dehydration–water evaporating too rapidly through the leaves and from the potting soil. Compounding that problem is that terra cotta and metal pots heat up and can “cook” the roots.

However, one way to help your potted plants survive on the patio in summer is to set each pot in a second, larger container. Then put an insulating layer of dried moss or coarse organic mulch between the two pots. This will keep the inner pot cooler and protect plant roots from sizzling heat. You may want to try to keep the insulating layer damp–but beware of soaking it because the water could pool inside the outer pot and soak up into the inner one. You could end up drowning the plants from the bottom.

Consider using one of the newer plastic pots as your outer pot. They are far more attractive than they used to be and conduct far less heat than terra cotta pots. The insulation may also be helpful in winter, if you live in an area where it freezes in winter.

Controversial polymers

Polymers, those water-retaining gel crystals, are frequently used in flower pots to help cut down on watering and retain water in the soil for the plants’ use. This isn’t an instant solution, but polymers can help over a longer term–like all those hot days ahead of us here in the Sonoran and Mojave deserts.

Recently, however, we heard a gardener advocate using water-retaining polymers in flower beds and in the soil around trees.  It sounded like a good idea — particularly in a climate where water evaporates out of the soil so rapidly.

But a little online research revealed a preliminary study which indicates that polymers may break down in our native soils into chemical components which may not be all that good for plants and people. So while polymers may be a great solution for flowering ornamental plants in pots, stick with adding organic amendments, such as crushed pecan hulls or finely ground wood chips, to your garden’s natural soil to increase its water-retaining ability. Moreover, organic amendments add nutrients to the soil, which polymers don’t. If you would like to review the research yourself, to go Google and search for: “Polymers Gardening.”

And if the heat kills most of your plants–which is happening in many gardens here in Tucson now–you can replant in late September or early October.

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