14 Ways to Protect Your Vegetable Garden During a Heat Wave

1. Grow Heat-Tolerant Crops

Some vegetables are better suited to hot weather than others.

Cold-tolerant crops such as lettuce, radishes, carrots, beets, and brassicas are more likely to bolt during summer. It is generally better to grow these crops in spring and autumn and use heat-tolerant vegetables during summer.

Good summer choices include tomatoes, peppers, eggplants, sweet potatoes, okra, squash, pumpkins, cucumbers, and melons.

For heat-sensitive crops, succession planting can keep garden beds productive even when earlier plants begin to bolt.

Heat-resistant cultivars can also perform better in hot weather. Examples include 'Red Fire' and 'Jericho' lettuce, 'Rattlesnake' pole beans, 'Jade' green beans, and heat-resistant tomatoes such as 'Heat-Master' and 'Solar Fire'.

2. Wait to Plant

Avoid planting seeds or transplanting seedlings during the hottest periods of summer, even when growing heat-tolerant crops.

Young plants require more water and attention during extreme heat, and some seeds may fail to germinate when temperatures become too high.

3. Know the Signs of Heat Stress

Most vegetables can tolerate some heat, but extreme temperatures can cause plant stress.

Warning signs include:

Dropping leaves
Dropping flowers
Premature fruit drop
Wilted leaves
Drooping stems
Blossom end rot
Bitter or bolted plants
Hollow fruit, such as cucumbers

These symptoms can indicate heat stress or insufficient water.

4. Add Compost

Mix compost into garden soil or potting mix before planting.

Compost provides additional nutrients and helps soil retain moisture, reducing water loss during hot weather.

5. Apply Mulch

Apply a 2- to 4-inch layer of natural mulch around plants.

Mulch helps retain soil moisture and keeps plant roots cooler during summer.

Light-colored mulch, such as straw, can reflect sunlight and further reduce the risk of overheating roots.

Remove weeds regularly because weeds grow vigorously during summer and compete with vegetables for water, nutrients, and space.

6. Water Correctly

Proper watering is essential for preventing heat and water stress.

Check the soil before watering and water when the top 1 to 2 inches of soil feel dry. During extreme heat, container plants may need to be watered multiple times per day.

Slow, deep watering is preferable to frequent shallow watering. Use drip irrigation or direct water toward the plant roots rather than wetting the leaves and fruit.

Early morning or early evening is generally the best time to water. Watering during the hottest part of the day increases evaporation and can result in greater water loss.

7. Let Plants Breathe

If plants are growing under row covers, grow tunnels, or cold frames, open or remove the coverings during hot weather.

Enclosed coverings can create a greenhouse effect, causing plants to overheat and wilt.

8. Avoid Fertilizing

Avoid fertilizing during extreme heat.

Plants become less effective at absorbing fertilizer as temperatures rise, and fertilizing during heat waves can increase the risk of fertilizer burn and additional plant stress.

9. Don't Prune

Avoid pruning vegetables during periods of extreme heat.

Pruning can increase plant stress. Wait until temperatures become cooler before pruning plants such as tomatoes.

10. Move Vermicomposters

If you use an outdoor worm composting bin, move it to a shady location before temperatures become extreme.

Composting worms are sensitive to heat and may not survive if their containers become too hot.

11. Harvest Often

Regular harvesting is especially important during extreme heat.

Harvesting ripe fruit, such as tomatoes, helps plants conserve energy and reduce water loss.

Pests can also become more active during hot weather, so frequent harvesting can help protect crops from damage.

12. Install Shade Cloth

Shade cloth can be placed over gardens and containers before a heat wave to provide shade and reduce water loss.

Shade cloth that blocks about 30% of sunlight is suitable for many plants. Heat-sensitive crops such as lettuce may benefit from 50% to 70% shade.

Remove the shade cloth after the heat wave has passed.

In climates that regularly experience extreme heat, consider placing the vegetable garden where it receives some afternoon shade.

13. Provide Water for Wildlife

Birds and other wildlife may eat tomatoes and other fruits during hot weather while searching for sources of moisture.

A birdbath near the garden can provide fresh water and may reduce pressure on crops.

Hummingbird feeders can provide additional water sources for hummingbirds. A shallow, wet area of bare soil can also serve as a simple puddling area for butterflies.