Should You Cut Back Heat-Damaged Plants in September? A North Texas Guide

DFW summer heat damages garden and plants, how to recover for fall.

It’s been a brutal summer here in the DFW area. Soaring temps coupled with zero rain really did a number on our gardens, mine included.

If your plants are brown, leggy or partially bare after months of intense heat, it can be tempting to just cut everything back. But pruning a stressed plant at the wrong time can make recovery more difficult.

Here’s how to decide what to cut back, what to leave alone, and how to help your garden recover for fall.

How to tell whether a plant is dead or heat-stressed

Brown leaves do not necessarily mean a plant is dead. Before removing it, inspect the stems and the base of the plant.

Gently scratch a small section of stem with your fingernail. Green tissue beneath the surface indicates that the stem is still alive. You may also find healthy buds or new growth near the base, even when the upper portion looks completely dead.

If the stems are brown and brittle all the way to the ground and the crown shows no signs of life, the plant may not have survived.

When in doubt, give perennials and shrubs more time. Their roots may still be alive even if their foliage looks terrible.

What you can cut back now

Remove dead, broken or diseased growth from any plant. This improves its appearance and makes it easier to monitor for new growth. If you kept your tomatoes in the ground through summer, cut them back by one-half to two-thirds to encourage fall production and remove heat-damaged and disease-damaged foliage.

Leggy annuals and many herbaceous perennials can also receive a light trim. Remove spent flowers and reduce excessive growth by approximately one-third, making each cut just above a healthy leaf or bud.

July is typically the best time of year for cutting back perennials in North Texas, but our record-breaking heat this summer means plants are in need of a little extra TLC as we move into fall.

Avoid cutting plants nearly to the ground unless you know the plant responds well to that treatment. A moderate trim is usually enough to encourage fresh fall growth without placing additional strain on the roots.

This week I am trimming back my Salvia ‘Mystic Spires Blue’ by one-third to one-half and cutting my Echinacea purpurea down to basal foliage. I also plan to cut back my Crossvine to encourage a fall bloom once things cool off.

What you should leave alone

Do not prune trees, shrubs or other woody plants simply because their foliage looks scorched. They may need their remaining leaves to continue producing energy and recover from summer.

Spring-flowering shrubs should also be left alone because they may already be developing next year’s flower buds. Pruning them in the fall could reduce spring blooms. (These shrubs should only be pruned after spring bloom.)

Severely wilted plants should be stabilized before they are pruned. Correct the watering problem first, then wait to see which portions recover.

Sprinklers can take care of your lawn, shrubs, trees and other permanent plantings, but annuals, vegetables and container plants require daily watering by hand in order to supply enough water during this period of drought.

How to help plants recover for fall

After removing damaged growth, water deeply. Every time you water, your goal should be to deliver enough water so that the soil six inches below the surface is moistened. This is how to ensure that the plant roots are actually getting water. Frequent, shallow waterings never reach the roots.

Maintain a two- to three-inch layer of mulch, keeping it away from stems and plant crowns. Mulch moderates soil temperature and slows moisture loss while plants recover. Shredded hardwood is the mulch we recommend because it forms a dense mat that retains moisture and smothers weeds.

Despite the generic advice you might find online, don’t stop fertilizing your plants. With all this extra watering, nutrients are leeching out of the soil faster than normal. Be sure to use organic fertilizers only because chemical and synthetic fertilizers are often too strong for heat-stressed plants.

Our gardens will bounce back once the fall rains arrive and temperatures begin to fall. Just do your best to keep permanent plantings alive until then.

Need more help?

Not sure which plants to cut back, remove, or give more time? Students enrolled in The Dallas Garden School can post photos and questions in our private community and receive personalized help through Ask Callie.

Enrollment also includes our complete library of North Texas gardening classes, upcoming live classes and step-by-step seasonal guidance. Join The Dallas Garden School and get the support you need to help your garden recover and prepare for fall.

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Callie Works-Leary
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