Should You Harvest Your Veggies Before a Heat Wave? Gardening Pros Weigh In

Extremely hot weather is tough, even on mature vegetable plants that are at or close to the harvest stage. When temperatures remain above 90°F for two or more consecutive days, even heat-loving crops like tomatoes may show signs of heat stress, which can affect the quality of the fruit. 

Read on to find out which veggies you should pick promptly when a heat wave is in the forecast, which veggies are better left on the plants, and how to give your garden the best possible care in sweltering hot weather.

When and What to Harvest Before a Heat Wave

It’s better to harvest certain crops before a heat wave because the intense weather can leave your homegrown ingredients tasting worse for wear.

Crops Prone to Bolting

Pick any crops that tend to bolt under heat stress. Bolting is premature flowering in warm or hot weather. It mostly occurs in cool-season vegetables such as broccoli, cauliflower, lettuce, and spinach, but also in herbs such as cilantro and basil.

Cut the herbs back to prevent the development of flower buds.

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Tomatoes

Extreme heat may cause tomatoes to develop sunscald, crack, ripen more slowly, or not at all. Harvest any tomatoes that have started to change color and let them ripen indoors at temperatures between 70 and 75°F. They should have the same flavor as vine-ripened tomatoes.

Melons and Cantaloupes

Melons are prone to getting sunburn and becoming overripe. Once they easily pull away from the vine, they are ready to be picked. Cantaloupe-style melons have been bred to ripen off the vine; just let them ripen on the kitchen counter.

When and What to Harvest After a Heat Wave

Some crops are more tolerant and resistant to heat stress, and can be left on the vine until after the heat wave has passed.

Heat-Tolerant Plants

Crops that tolerate hot weather well should be left on the vine until after the heat wave; this include peppers and okra.

Peppers may drop their blossoms in temperatures above 90°F—and heat tends to slow down fruit growth—but you don’t need to rush to pick them before a heat wave once the fruit is fully developed.

Undersized Crops

Cucumbers and zucchini should be picked when they are slightly immature, but if the fruit is still tiny, it’s better to leave it on the plant and wait. If you keep these plants well-watered during a heat wave, it won’t take more than a couple of days for the fruit to reach a harvestable size. 

Crops That Don’t Ripen Off the Plant

Unlike melons and cantaloupes, watermelons do not ripen after picking, so if they don’t show the typical signs of ripeness—like brown tendrils and changing rind color on the bottom—leave them on the plant and wait.

The same applies to eggplant, which can be picked when slightly underripe but not when immature.

6 Tips for Managing a Veggie Garden Through a Heat Wave

It’s important to help support your garden through a heat wave; here are six things you can do to keep your plants and crops thriving.

Water

Keeping your plants well-watered is the single most important thing to do during a heat wave.

Water slowly and deeply enough to saturate the entire root zone. Tailor your watering to the type of vegetable; some vegetables, such as lettuce, have shallow roots, and root vegetables like carrots have long taproots.

Water preferably in the morning and, if needed, again in the evening. Wilted plants should be watered immediately.

Mulch

Add a layer of organic mulch around the base of the plants to conserve soil moisture and suppress weeds.

Provide Shade

The ideal way to provide permanent protection for heat-sensitive veggie plants is to install a shade cloth or shade fabric. It blocks a percentage of the sun’s rays and reduces heat stress.

In a pinch, you can use a beach umbrella instead, but keep in mind it deprives the plant of direct sunlight. so you should only set it up during the hot afternoon hours.

Keep Your Garden Free of Weeds

Weeds thrive even when other plants languish. They compete with your vegetables for water, nutrients, and space.

Garden beds that are free of weeds are much better prepared for a heat wave than those overgrown with weeds, which also make harvesting cumbersome.

Back Off Any Fertilizer and Chemicals

During periods of intense heat, don’t use any fertilizer; you don’t want to encourage new growth in a plant that is mobilizing all its reserves to survive.

If you detect pests or diseases on a plant, treating it with any products—conventional or organic—may cause damage in hot weather. Check the product label for specific details.

Don’t Overprune

Resist the urge to remove foliage that looks unsightly, as it still does its job of shading the remaining plant, including the fruit. Overpruning may cause sunscald.