Gardening in Extreme Heat

Gardening in extreme heat is a common issue for Zones 9 and 10 growers. In fact, extreme heat can be common in many areas of the southern United States from June through late fall. For gardeners in Southern California specifically, extreme heat can plague us from summer solstice until late October or even into November.

With global warming continuing to cause rises in temperatures, more and more people gardening in urban spaces, and the longer and more intense heat periods we are experiencing, knowing how to garden in extreme heat is a key skill you need throughout the growing season.

Here are our favorite tips when gardening in extreme heat to make your gardening experience much more successful.

Gardening in Extreme Heat: Soil is Your Savior

The better your soil, the more crops you can grow during extreme heat events or a particularly hot summer. If you invest time and money in your soil, your soil will hold more moisture for longer periods, have a more robust microbiology, and help to repair plants after extreme heat stress. Soil that can handle extreme heat has these characteristics — it holds onto moisture for a maximum amount of time between waterings, is alive and teaming with microbes, and has a healthy supply of plant food to help plants grow and repair damaged cells after extreme heat.

Compost is, by far, the most important component of good soil when gardening in extreme heat. It can hold up to 40x more moisture than regular soil! It will take longer to dry out between waterings, which is essential. Compost with a high capacity to hold water must be biologically rich. In other words, it must be alive and teeming with microbiology like mycelium, bacteria, and all the parts of a healthy soil food web. Each component of the soil food web holds onto moisture, giving your compost and soil more moisture-holding capacity. To make that happen in your backyard garden, you will want to use compost from your own compost heap as it tends to be the most microbiologically rich. However, it is unlikely that you will make enough compost in your home garden for your needs, so supplement with buying compost or getting it from your local municipal program. If you are unsure that your soil is bursting with microbiology (store-bought products are usually not), use compost/worm tea and worm castings to inoculate your soil with the healthy bacteria you need to keep your plants alive during summer heat stress.

Gardening in Extreme Heat: Protecting Your Plants from Extreme UV Rays

We have all shielded ourselves from the sun’s powerful UV rays and can do the same for our plants. Granted, slathering on sunscreen is not practical for plants! But you can give your plants sunscreen by hanging shade cloth, similar to us wearing protective clothing. Shade cloth is a woven fabric that deflects a portion of sunlight from your plants. It is not the same as a shade sail or awning sold at nurseries and big box stores. You will only find high-quality shade cloth made for growing agricultural products from companies that have it custom-made. Our shade cloth is designed for growing fruits, vegetables, and flowers in extreme heat. It blocks out 40% of the UV light and can be easily hung over crops and removed when the weather cools. The advantages of using shade cloth are numerous.

• Reduces the harshness of the UV light without blocking out all sunlight
• Reduces evaporation through plant cells
• Reduces evaporation of moisture in the soil
• Prevents sun scald

If you have not invested in shade cloth for your summer garden, it is one of our favorite tools that gets used every single year. We have tons of videos on our YouTube channel about shade cloth. Check this one out:

Gardening in Extreme Heat: Reducing or Blocking Plants from Hot, Drying Winds

The sun and extreme heat is only one part of what makes gardening so hard during hot spells. Hot drying winds like the Santa Anas are the other factor plaguing Southern California growers. These winds come from the east and suck moisture from plants at a very high rate. They often dry out the soil and plants quicker than you can keep up with watering. To reduce the amount of water evaporation from your plants and the soil, block drying winds from encountering your plants. To do so, stack haybales around your plants or set up a similar wind block to stop the dry, hot air from hitting your plants. We learned this awesome tip from a fabulous read, Growing Vegetables in Drought, Desert & Dry Times. Although it may seem silly or impractical, the idea is simple. If you can reduce the amount of hot air hitting your plants by blocking the prevailing winds, you can reduce the amount of evaporation your plants will experience. Blocking and lessening the impact allows plants to grow through extreme heat with more energy, moisture, and the ability to bounce back.

Other ways to block the hot, drying sun include:

• Moving pots to another garden area.
• Setting up wind blocks with plywood.
• Using regular awning cloth or tarps to stop the drying winds.

Gardening in Extreme Heat: Mulch, Mulch, Mulch

Mulch is something that we talk about A LOT. That’s because, in the garden, it holds magical powers. It helps reduce the amount of moisture that comes out of the soil, protects the soil’s surface, creates a home for microbiology to thrive, keeps weeds at bay, and reduces soil temperature. That’s only a few of the benefits. When gardening in extreme heat, you should cover every inch of exposed soil with 6–12″ of mulch. This mulch will help accomplish all the above benefits and also break down to become compost. Check out our YouTube page for all our videos on the benefits of mulching and the kind of mulch we use.

Gardening in Extreme Heat: Grow the Right Varieties and Crops

Even if you employ all these tips in your garden but are growing the wrong plants that can’t hang with the heat, you will not be successful. Remember that during the warm season, you will only want to grow warm-season crops like:

• Beans
• Corn
• Cucumbers
• Eggplant
• Melon
• Okra
• Peppers
• Pumpkins
• Squash
• Tomatillos
• Tomatoes

Shop all our summer seeds here.

These crops enjoy warm weather and longer days of sunlight. They will be affected by extreme heat but not to the extent that year-round crops will be, such as:

• Greens/lettuces
• Root crops (beets, carrots, radishes)

Although it is possible to grow these year-round, these crops prefer mild weather and will not be able to grow well during extreme heat events.

Lastly, shop for “drought tolerant” or “heat tolerant” varieties if your summers are very hot, and you know that you will have a chunk of summer days with weather above 100 degrees. These are varieties that do well in above-average temperatures. Make sure you utilize all of the tips we gave you above to provide these varieties with the best chance!