Gardening in Extreme Heat: What to Do During a Heatwave
Gardening during a heatwave requires quick thinking and a few adjustments to your normal routine. Heatwaves are tough on all of us, and they’re just as hard on our gardens.
In the record-breaking summer of 2024, Phoenix experienced 113 days with temperatures over 100°F (38°C), with 70 of those days reaching 110°F (43°C) or higher. That kind of heat can quickly overwhelm even a well-established garden.
Gardening in extreme heat isn’t easy, but with the right strategies, your plants can pull through. In this post, I’ll walk you through what to do (and what not to do) during a heatwave. A free printable PDF is also available at the top of this post.
What we will cover:
- Why Heatwaves Are So Hard on Plants
- The Best Defense Starts Before the Heat
- What to Do During a Heatwave
- What NOT to Do During a Heatwave
- FAQs about Gardening During a Heatwave
- Summary: What to Do and What Not to Do
- After the Heatwave: Evaluate & Plan Ahead
- Additional high-heat gardening resources:
Why Heatwaves Are So Hard on Plants
When it gets this hot, plants shut down normal functions just to survive. It can be discouraging to walk outside and see everything wilted. Gardening during a heatwave isn’t easy.
Normally, they release water vapor through their leaves to stay cool. This is called transpiration. But in extreme heat, they stop that process to conserve moisture. That means:
- No cooling
- No growing
- No photosynthesis
Most plants start to suffer when leaf temperatures reach 115°F (46°C). Some heat-loving plants can handle it, but many crops, especially cool-season ones, cannot.
An extreme heatwave separates warm-loving crops from those that thrive in heat. Typical warm-season crops like squash, tomatoes, cucumbers, and green beans may struggle during high heat. If the heatwave is temporary, these guidelines may help the warm-season crops survive until temperatures moderate.
The Best Defense Starts Before the Heat
Just like people prepare for emergencies in advance, your garden needs a strong foundation before the hottest days hit. That includes:
- Planting at the right time so roots are well-established
- Watering deeply to encourage roots to grow down into cooler soil
- Using healthy, well-draining soil
- Choosing heat-tolerant plants
- Placing plants in locations with appropriate sunlight exposure.
Smart Plant Selection for Heatwave Survival: Heat-loving crops include okra, amaranth, sesame, basil, cowpeas, roselle hibiscus, and sweet potatoes. Learn more about these heat-loving crops in this blog post. Focus on plants known for heatwave survival.
If you’ve done these things, your garden already has a better chance. But if you haven’t, don’t give up. There are still steps you can take when extreme heat hits.
What to Do During a Heatwave
1. Watering Plants in Extreme Heat
One of the most important tasks during a heatwave is proper watering.
Check the soil each morning. If it’s still hydrated, hold off on watering. If the soil is dry, soak deeply so water reaches the root zone. This helps plants stay hydrated throughout the day and encourages deep root growth
Young trees and shrubs also need deep, slow watering at the drip line where the roots are growing.
Overwatering during heat stress can cause root issues. A wilted plant may not need water, check the soil first!
Learn more about the best way to water raised beds in this blog post. Learn more watering principles in this blog post.
2. Use Mulch to Protect Garden from Heat
Apply a 3 to 4 inch layer of mulch to garden beds before summer heat arrives.
Mulch helps protect your garden by covering the soil surface, reducing evaporation, and keeping the root zone cooler. This helps moisture stay where roots need it and prevents extreme temperature swings that can stress plants.
Mulch is not just for vegetable beds. Trees, shrubs, and native plants also benefit from improved moisture retention and more stable soil temperatures.
Learn more about the best types of mulch for hot climates in this article.
If you would like to learn more about the principles of successful desert gardening, my guide, “Desert Gardening: How to Grow Vegetables in a Hot, Dry Climate,” may be helpful.
3. Provide Shade to Protect Plants from Summer Heat
Shade can make a big difference in how plants handle high temperatures. It lowers leaf temperatures and helps prevent sunburn and heat stress. Even a few hours of protection from the intense afternoon sun can be enough to help plants survive. Young trees especially benefit from extra protection while they are getting established.
You don’t need fancy materials. Use what you have:
- 50% white shade cloth is ideal because it filters sunlight while still allowing plants to grow
- Old sheets, patio umbrellas, or even temporary canopies work in a pinch
- During a heatwave, adding extra shade can help plants pull through
In my garden, I like to plant sunflowers on the west side of raised beds to create natural afternoon shade.
Shade structures don’t have to be permanent. A simple setup using hoops, clips, or repurposed materials can make a difference.
Other Shade Resources:
- Why Add Shade to Your Garden in Summer
- Which Vegetables Need Shade (and Which Thrive in Full Sun)
- How to Create Garden Shade for Heat Protection
4. Support Containers During a Heatwave
- Use ollas or watering spikes to deliver steady moisture
- Group containers together to create a humid microclimate
- Move pots to the north side of walls or into shaded areas
Consider adding ollas to containers to provide a moisture reserve from which the roots can draw. I use the ollas from Growoya
5. Garden Triage: Focus on What Can Survive
Even if you do everything right, it may still not be enough. That is when it helps to look at the bigger picture. Gardening in 110°F weather requires tough decisions.
Think of it like garden triage. You don’t have to save everything. Focus your efforts on:
- Established perennials
- Fruit trees
- Truly heat-tolerant crops like okra, basil, sweet potatoes, and amaranth
After the brutally hot summer of 2020, someone at one of my fall gardening classes asked,
“If you had known how hot this summer would be, what would you have done differently?”
My answer was simple. I would have leaned more into heat-loving cover crops and stressed less about keeping everything alive. That question helped me realize that letting a space rest isn’t a sign of giving up. Sometimes, planting a cover crop and letting that area go for the season is the smartest move.
What NOT to Do During a Heatwave
These are common mistakes that can cause more harm than good during extreme heat.
Don’t prune
Leaves shade stems and fruit. Removing them can expose plants to sunscald, similar to frost damage. Damaged leaves protect the plant from worse injury.
Don’t fertilize
Fertilizer encourages new growth, and that tender new growth is especially vulnerable to heat damage. Wait until temperatures cool and plants begin growing again.
Don’t plant new crops
Seedlings and transplants have very little chance of surviving a heatwave. Delay planting until the weather stabilizes.
Don’t expect perfect harvests
Many plants stop flowering or drop blossoms during extreme heat as a survival response. This is normal. Once it cools down, they will likely begin producing again.
Don’t forget trees and shrubs
Give deep, slow water at the drip line and mulch well. Shade young trees when possible to reduce heat stress as they establish.
FAQs about Gardening During a Heatwave
What is the best time to water during a heatwave?
Early in the morning. This reduces evaporation and helps plants start the day fully hydrated.
Can I mist my plants?
Yes, especially in dry climates. Mist in the late afternoon, but allow time for leaves to dry before dark.
How can I tell if I’m overwatering?
Check the soil 1-2 inches down. If it’s still moist, wait. Wilting does not always mean the soil is dry.
What plants survive heat waves best?
Okra, sweet potatoes, basil, amaranth, roselle hibiscus, and many native or desert-adapted perennials.
Is it too late to help my plants?
If they are still alive, it is not too late. Prioritize shade, water, and mulch.
Why are my plants wilting even though I watered them?
They may be suffering from heat stress, not water stress. If they perk up overnight, it means they are adjusting to the heat. Always check the soil before watering.
Should I cover all my plants with shade cloth?
Not necessarily, but even heat-loving plants benefit from protection during extreme conditions. Afternoon shade is most helpful.
How do I know if I’m overwatering?
Feel the soil an inch or two deep. If it’s moist, do not water. Roots need both water and air. Too much water can drown the roots.
Summary: What to Do and What Not to Do
What to Do
- Water deeply in the early morning
- Check the soil before watering wilted plants
- Apply 3–4 inches of mulch
- Add afternoon shade using cloth or structures
- Group and shade containers
- Use ollas or watering spikes
- Mist leaves in the afternoon
- Focus on heat-tolerant plants
- Let areas rest with cover crops
What NOT to Do
- Don’t expect perfect harvests
- Don’t prune
- Don’t fertilize
- Don’t plant during extreme heat
- Don’t overwater wilted plants without checking the soil
After the Heatwave: Evaluate & Plan Ahead
Although it may feel endless, heat waves don’t last forever. Once temperatures return to normal, take a few minutes to assess how your garden handled the stress.
- Which plants thrived, and which struggled?
- Which parts of your yard or garden received too much sun or heat?
- Did your shade strategies and watering techniques work well?
Use what you learn to plan for next time.
Additional high-heat gardening resources:
- 10 Ways to Help Your Garden Survive Summer
- Adding Shade Cloth to a Hot Summer Garden
- 10 Ways to Prepare Your Hot-Climate Garden for Summer
- 10 Flowers that Love Hot Summers – and How to Grow Them
- Summer Gardening in Arizona
- Summer Gardening in a Hot Climate (Playlist on YouTube)
- Elevated Garden Bed Tips for Hot Climates
Here in southern New Mexico we are currently experiencing a heat wave. 104 yesterday, 6/05. 106 predicted today, 6/6.. Forecast says it will go back into the upper 90’s by Monday, 6/10. My question is WHEN can I fertilize tomatoes and peppers in CONTAINERS? Is upper 90’s considered “over the heat wave”? Last summer we had 100 plus temperatures every day from the third week of June until the first part of August when it cooled down to upper 90’s, but we still had 100 plus temperatures several days of August going into the second week of September.
One suggestion given me was try fertilizing at night when the temperatures will be cooler for a while. (Our night temperatures have been in 60’s and probably will occasionally be in the 70’s during the summer.) Another suggestion given me was just use half strength fertilizer.
I use organic Neptune’s Harvest Tomato & Veg 2-4-2. I also put organic granular fertilizer in the potting mix when I transplanted. Is using the granular counted as “not fertilizing”?
I suppose the bottom line is if I wait until the temperatures drop into the lower 90’s or so I probably won’t be fertilizing until September. This has been confusing for me.
Thank you,
Sharon White
Good questions. The NPK numbers on that fertilizer are very, they are less likely to burn that way. I would use a half-dose as needed.