5 Gardening Tips For A Heat Wave

Mid-summer means there is a threat for heat waves in many climates. From Texas all the way to our garden here in New England, heat waves can hit pretty much anywhere.

High temps can cause stress on most plants. Anything above 90°F, and your plants will start to suffer. It also becomes a chore to water the garden much more frequently (who wants to spend hours watering every week?). So, in this article I’ll share five essential tips for your garden during a heat wave.

Potted plant in heat wave

How Hot Is Too Hot For The Garden?

Most summer vegetables like temperatures between 70-90°F. Temperatures above 90°F are considered excessive for most plants and will lead to signs of stress.

Signs of heat stress:

  • Flower drop
  • Drooping leaves
  • Excessive water usage
  • Sun scald

I live in New England where the summertime temperatures are typically in the 70s and 80s. But, we usually get at least 1 or 2 heat waves where temperatures go into the mid-90s and above for several days.

So, whether you live in a naturally hot climate (such as Arizona or Texas), or you’re expecting a heatwaves, these tips will help your garden get through.

1. Water Deeply and Slowly

When it is hot, plants use more water. All plants “transpire” water through their leaves. This is basically the equivalent of sweating out extra water to stay cool. As a result, you may need to water daily to keep your plants hydrated.

One of the best ways to lower your need to water is to water deep and slow. Many beginner gardeners make the mistake of watering quickly and heavily with a watering can or hose. This causes a surface-level watering that does not penetrate deeply underground.

Always water slowly and for a longer period of time. This ensures that the water doesn’t run like a river away from your garden. Instead, you want it to stay near the root system and travel deep underground.

Shallow watering leads to a shallow root system. Deep watering leads to a deeper, larger root system. A deep root system is able to access water deeper underground, and is more resilient in a heat wave. The result is much less frequent watering.

Deep watering root system graphic
Deep, slow watering leads to a larger, deeper root system.

If you are able to water deeply, you won’t need to water as much! Before you water, check the soil to see if there are signs of moisture a few inches down. If it is still moist, hold off on watering and let your plants use the available water in the soil, first.

Try drip irrigation

If you have a huge garden, it may be worth it to install drip irrigation. These plastic tubes are laid out around the garden, and holes in the tubes deliver water right at the base of the plants. The best part is that all you have to do is turn on the hose and wait.

The initial cost and setup is one downside, which can be a bit tedious. Once installed, the system will water everything at once, so you won’t be able to selectively water with the drip irrigation. You also need to have access to a water spigot to deliver the water. However, once installed, drip irrigation makes watering super easy.

Drip irrigation is especially great if you live in an arid climate that doesn’t get much rainfall. Or, if you’re growing in containers, you can save a lot of time watering each day. I don’t currently use drip irrigation since our garden isn’t too large. But as we add more raised beds, I’m considering it more every year. It definitely saves a lot of time!

2. Mulch Plants

Mulching your garden is another way to protect your plants from hot weather. Having a nice thick layer of straw, dried leaves, or wood chips helps insulate the soil. This barrier leads to less water evaporation, and prevents the soil from changing temperatures drastically.

Straw mulch around garlic

Essentially, when it gets really hot, the mulch keeps the soil cool (which is what plants like). If the soil gets overly hot, more water is evaporated, and the plants become more stressed.

My favorite reason for mulching is that it saves time weeding (who wants to pull weeds in 90° heat?!). So, adding a natural mulch around your plants will benefit you in a number of ways, especially during a heat wave.

3. Shade Vulnerable Plants

Shade cloth is essential if you live in a very hot climate. If your summer temperatures are consistently over 90°F, it might be worth installing a retractable shade covering. There are many ways to achieve this, from simple to complex.

Shade can cool your plants off by several degrees. This can be enough to prevent flower drop and reduce sun scald on tomatoes and peppers. If you’re growing heat-sensitive crops like leafy greens, it can also prevent bolting.

Shade cloth in garden during heat wave
White shade cloth (50%) from Bootstrap Farmer.

In my garden, I use shade cloth during heat waves over peppers, tomatoes and any other fruiting plants. This gives me peace of mind that the plants won’t drop their fruits during the hot weather, and will continue to produce. It is also great to use during the hardening off period to avoid leaf scorch.

To apply shade cloth, I drape it over our low tunnels. This is great for shorter plants, but may not be tall enough for everything that needs shading. For taller plants, you can either drape it directly over the plants, or ideally suspend it several feet above the garden using T-posts or poles.

There are also different types of shade cloth, anywhere from 30% to 90%. The hotter your climate, the higher percentage to use. If you’re unsure, I recommend starting with 50% shade cloth.

Alternative: Use Kaolin Clay

If shade cloth isn’t for you, there is another little-known method of cooling off plants. Kaolin clay is a natural white clay that is used to deter beetles from chewing on plant leaves. But it also cools off plants by making the leaves white, which reflects more of the heat from the sun.

Kaolin clay on cucumber seedling
Kaolin clay sprayed on young cucumber seedling.

One great example of using Kaolin clay this way is for my rocoto peppers. These peppers come from a cooler climate, and do not tolerate heat well at all. So, I spray my rocotos with Kaolin clay before a heat wave to keep the plants happy.

The only drawback of Kaolin clay is that it can be a bit ugly after spraying the plants. I don’t usually spray it on flowers or other ornamentals for this reason.

4. Try Self-Watering Containers

If you love growing in containers, then self-watering containers can save you a lot of time watering. These pots essentially provide water from the bottom rather than the top. The soil wicks up the water from a container below, hydrating the soil for longer.

You can easily make your own self watering container, or you can find them online. We grew a huge pepper plant in a 17 gallon self-watering pot. The plants required almost no watering, other than topping off the bottom container about once a week or so (even in a heat wave!). Learn how to make one here.

Transplanting pepper into self-watering container
Homemade self-watering container.

5. Be Prepared

No garden will thrive without you to help it along! Even when it gets super hot, we have to brave the heat and get into the garden anyway. Tomatoes and cucumbers won’t prune themselves, so when you do go outside, be prepared.

Tips for gardening in high heat:

  • Garden in the morning or evening. Morning and evening are the best times to get into the garden. Plan your gardening time to take advantage of the cooler temperatures.
  • Drink water and take breaks. If you’ve got a lot to do, make sure to take breaks to catch your breath and drink more water. Staying hydrated can be a challenge when you’re dripping in sweat.
  • Wear a hat. I like to wear a big, doofy gardening hat whenever the sun is shining. This portable shade source can keep you going longer, and prevent sunburn on your face and head.
  • Wait, if you can. Not everything needs to get done today. Believe me, I know it’s easy to get carried away with gardening tasks. But if you find yourself in the garden in intense heat, take care of the essentials only. The rest can wait.

I hope you find this article useful when you’re gardening in the summer heat! Hot temperatures can make it a challenge in the garden. These tips have helped me save time and get bigger yields in the end.

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