Before going into how to protect your garden from a heatwave, how about we talk about the definition of a “heatwave”.  According to the National Weather Service, a heatwave is “a period of unusually hot weather that typically lasts two or more days.” In my opinion, there can even be “heatwaves” in Winter because sometimes we get hotter than usual temperatures that Winter/Cool season crops can’t withstand. Essentially, whenever the temperatures will be hotter than unusual in relation to the season we are growing in (either Summer or Winter), I prepare my garden for a heatwave.

What is Your Garden Zone?

To give you some perspective, our county has frequently hit temperatures anywhere from 100-112 degrees F in the Summer during heatwaves. On these insanely hot days I like to take extra steps to protect my garden from a heatwave. To start, I’d like to draw your attention to gardening zones. For the most part, I garden according to my garden zone (10b), so most of the plants I grow are well accustomed to heat and the intricacies of our climate.  My first piece of advice is to know your garden zone, so that you can spend less time trying to save your plants and more time growing things that are used to your climate.

You can look up your gardening zone HERE and read about how I use that information to plan a garden. 

Despite aiming to grow plants that are well-suited to Southern California, every gardening zone will occasionally be hit with extreme temperatures….that’s where these tips come in handy!

1) Shade your garden

My favorite wat to protect my garden from a heatwave is to create shade! It’s time to construct some temporary shade for your garden. You can get creative and use whatever you have available—tarps, old sheets, drop cloths, or shade cloth. For the last few years, we have kept mesh tarps from Harbor Freight in our garage. Not only have they come in handy during heatwaves, but I’ve used them to protect my seedlings and even to cover our apricot tree to keep birds away. Honestly, I love keeping versatile items like this in my gardening toolkit! Update: I finally invested in row cover fabric for my cool season garden! This Summer I plan to use my DIY hoops and cover fabric to help shade the garden on hot days. You can view the full DIY row cover tutorial HERE.

No matter what type of covering you are using, it’s important to avoid creating a hot greenhouse environment that can become an “oven” for your plants. Avoid this by making sure there is airflow between the plants and your cover, and not enclosing the plants on all sides. NOTE: when using row covers for hot days, this can be accomplished by clipping up the edges of your fabric and creating only a cover above the vegetables like in the photo below.

Many cloths/coverings on the market come with a rating for how much sun it blocks out—the black mesh tarps we have block out 60-70%, while this top seller on Amazon blocks out 40%. You can decide what would work best for your garden. I use the shade cloths only on exceptionally hot days, so I go with the 60-70% block capability for such rare circumstances. If you were to use shade mesh for the whole Summer season (semi-permanently) then I would select one that blocks out only 40%.

Lastly, there are many ways to mount/install shade cloth to protect your garden from a heatwave, but in a pinch I’ve even used old tomato cages placed in the garden and draped the shade cloth over them. 

Do I need to shade & protect everything?

Nope.  My landscaping (which is now mostly native plants anyway), doesn’t need any protection. Like I said before, I really try and select plants that are drought tolerant, heat loving, and meant for my climate. Many mature or large plants won’t need special attention. For example, I have a whole bed of large tomatoes and squash which are summer veggies to begin with. They are so large that they kind of shade each other and already have a well-established root system to survive hot days. I basically aim to provide some shade to small, growing veggies (ones that aren’t fully grown, vegetables that might be “out of season” technically—like lettuce and radishes—or some of my more delicate herbs. I have seen my basil perform better when I give it some shade on the hottest days. My peppers even tend to do best with some shade. Get to know your garden, and over time you’ll know 😉

Related Article: 10 Heat-Loving Vegetables & Flowers to Grow From Seed

2) Water deeply before a heatwave

If you know about the heatwave beforehand (anyone else check the weather every day? haha), prep your garden by watering deeply at least once before the hottest day.

Water deeply, early in the morning, on the hottest day.

Early morning watering is generally best, as it allows the plant to prepare to battle the heat all day. 

3) Check Your Irrigation

Have you ever come home one day to find all your plants wilted? I have. It was because my irrigation broke! It’s smart to check your irrigation periodically to make sure everything is running properly. In order to protect my garden from a heatwave, I’ll try and turn on my irrigation periodically and check that all tubes are dripping, heads aren’t clogged, and that the timer is set properly. 

Are you curious about my irrigation setup and system? I wrote a full breakdown of the different ways we water the garden in: Watering & Irrigation Basics ~ Insights From Our Garden

In the photo below you can see our Garden Grid irrigation in one of our raised beds (LINK code: freckledcali10 for $10 off $100 or more) So far, I’ve found this to be an extremely dependable system and also helps you layout your crops efficiently. I talk more about this idea of “square foot” gardening in Tips for Creating a Garden Crop Plan & Layout.

4) Mulch

Mulch is basically a layer of organic material that you would spread over the surface of the soil in your garden. In my experience, mulch is one of the top things you can apply to the garden to protect your plants from a heatwave. 

All my favorite mulching tips and details are outlined in Let’s Talk Mulch! Mulching a Backyard Vegetable Garden.

Quick mulch ideas:

“Chop and drop” is one way to mulch your garden. For example, when clearing out plants, I sometimes will leave the foliage and stalks to cover the ground in the garden.

Dead leaves are also a good mulch material.

Wood chip mulch can also be purchased from a local landscape company or obtained from local tree trimmers, but sometimes wood chip mulch can attract earwigs and roly polies and cause more problems than it is worth.

Some gardeners use compost as mulch. The additional layer of decomposed materials can act as protection for the soil.

In my garden, I often plant things closer together than recommended. This is one thing I have learned over the years. When you plant your plants closer together, they grow closely and essentially mulch each other! Closely planted beds have perpetual shade on the soil, and lose a lot less water.

5) Prep your container plants

Truthfully, containers, pots, and hanging baskets are the most high maintenance in a garden because they often don’t retain water well and dry out fast.  While I do have potted plants, I find them to be the hardest to maintain during a hot Summer. In order to protect your container garden during a heatwave, water your container garden thoroughly before, during, and after a heat wave. If possible, move them into a shady area for the hottest days. Mobility is one of the advantages of container gardening for sure!

6) Do Not Prune or Fertilize

Sometimes the best way to protect your garden from a heatwave is to know what NOT to do. You might remember from my Growing Tomatoes FAQs that, in hotter climates, leaving the leaves on your tomatoes can actually protect them from sun-scald. Additionally, this works for a lot of plants in the garden as well. If you are expecting some intense heat and sun, wait to do any pruning. Let your plants shade themselves.

Pruning and fertilizing are both actions that stimulate growth—this means tender, fragile, green growth will appear. This new growth will suffer in the intense heat, so I recommend not pruning or fertilizing before or during a heatwave.

7) Pull plants that will bolt & harvest

This step is optional, but I wanted to note that there are some plants that won’t make it through the heat. Vegetables such as lettuces, radishes, napa cabbage, spinach, and other tender crops will most likely bolt and become bitter in the heat. If you would like to harvest them for eating, it’s often a good idea to do this before the heat hits. Again, this is optional. Sometimes I like to leave them in and see what happens. Bolting plants eventually put off flowers that the bees love and sometimes you can save seed as well. You should also plan to pick flowers or do a harvest when things are in their prime.

I hope these simple tips will help you feel prepared for Summer gardening. Growing in heat can indeed be challenging, but it is possible when you choose the right crops to grow and know how to protect your garden from a heatwave. If you need help selecting some vegetables and flowers that can tolerate heat, I encourage you to check out my list of Heat Loving Plants to Grow From Seed. Happy gardening!

Do you grow in hot summers? What are some of your favorite tips for Summer growing?⇓