10 ways to protect your plants in a heatwave

Consider containers and hanging baskets

We asked Janet Manning, RHS Garden Water Scientist, for her advice on protecting plants in containers in hot weather. She told us “When temperatures soar, we head into the shade. Plants can’t do that. But why not rearrange your pots in the shade for a few days until the heat passes? You’ll be amazed the reduction in water used and less stress for the plants. I gave up with hanging baskets years ago – I think it’s really time they went out of fashion. But if you really want to keep them, it’s got to be self-watering ones only so that you are keeping the root zone more evenly moist all the time.”

Watering techniques

Water plants less often, but more deeply, so that the water reaches plant roots and make sure plants are watered before a drought, rather than letting the soil get bone-dry before watering and subjecting plants to extremes. Mulch around plants to retain as much moisture in the soil as possible. Apply mulch after rainfall or watering, so that there's already moisture in the soil.

• How to be water-wise

Lawn care

In extreme heat and long periods without rain, lawns can turn brown. Don’t worry that the grass has died – it’s resilient and as soon as the rain returns, the grass will bounce back and you’ll have your lush green lawn again. For longer-term care, Janet suggests getting a hollow tine aerator and “aerating the lawn in the autumn and spring to de-compact the soil and let the rain penetrate.”

Create shade

One of the best ways to protect plants in hot weather is to create shade using garden fabric, cloches, or temporary covers. Janet’s advice is to “Pop up a sun shade, put washing on the line, throw a net curtain over them, push plants together in containers and shade the root zone with plenty of mulch.” But she also emphasises that “the environment and wildlife suffers in heatwaves and droughts too, and we shouldn’t be trading one for the other. The answer to that has to be re-using water, collected rain, sinks baths and shower water can all be used on our plants and it means no extra water is taken from our precious rivers to keep our plants alive.”

“And don’t keep soils saturated, in this heat, you just end up with roasted root soup! Roots need oxygen as much as water and at higher temperatures the oxygen is used up in the root zone more quickly. Saturating the soil with water just displaces even more air and roots are more at risk of waterlogging in a heatwave.”

5 long-term actions for future-proofing your garden

We’re seeing far more extreme weather conditions these days. Met Office Scientists recently published a report that shows an increased likelihood of extreme temperatures in the UK as a result of climate change. Their results indicate the chance of exceeding 40 degrees is now 20 times more likely than it was in the 1960s. In order to future-proof our gardens, we need to make changes before heatwaves occur so that our gardens require less water overall and our plants are less badly affected by extreme temperatures and droughts.

Choose heat- and drought-tolerant plants

Choosing suitable heat- and drought-tolerant plants for your soil conditions helps protect your garden from the detrimental effects of heatwaves. You might think of Mediterranean herbs, perennials with glaucous or silvery foliage, and ornamental grasses as good choices, but so much depends on the conditions in your garden. For this reason, Janet doesn’t recommend particular plants to people without knowing what the aspect and soil conditions are like.

She told us “Hostas are drought tolerant, as are salvias, but only if you put the hosta in the shade, and the salvia in a deep, sandy or chalky soil. Salvias are not drought-tolerant if you plant them in shallow soil. I made that mistake for years before I realised they have a deep root architecture. Yes, they have waxy coated small leaves for reducing their water use, but they also have really deep roots almost reaching 2m deep, which means they’re drawing water from a much larger volume of soil than the shallower roots you might find on a hosta. Understanding your soil depth, structure and texture is the key to drought tolerance, then choosing the right plant to match those things. It’s easier if you use the RHS ‘Find a plant’.”

• How to create a resilient garden

Reduce lawn areas

If you’re not keen on having a brown lawn during droughts and heatwaves, you could let the grass grow longer, which makes it more resilient to dry weather, or switch to more drought-tolerant alternatives. Try replacing your lawn with a gravel garden, Mediterranean-style border or a clover or thyme lawn. All these drought-tolerant alternatives are ideal for sunny spots where grass is likely to turn brown in the summer.

• How to create a drought-tolerant gravel garden

Rainwater harvesting

Install water butts before the summer weather begins – the bigger your containers and the more you have, the more rainwater you’ll save. Consider investing in irrigation systems such as drip irrigation too, which make it easier to use water efficiently by regulating amounts, delivering it to the root zone and timing your watering to take place in the coolest parts of the day.

Garden design tips

Consider water-wise design to future-proof your garden for our increasingly hot summers. Plant trees to create shade that will protect your other plants and group plants with similar watering requirements together. Make sure your plants are planted in the right place so they remain as healthy and resilient as possible.

• How resilient is your garden?

Building healthy soil

One of the best ways to protect plants is to build healthy soil that retains good levels of moisture. Janet explained “It’s not the watering technique that makes the biggest difference, it’s the cultivation techniques that don’t involve water at all. Mulch, mulch and more mulch keeps the soil insulated from the heat, and an organic mulch such as wood chip, straw or bark slowly feeds the soil to keep the soil healthy. Healthy soil means lots of soil life, all exuding substances into the root zone such as carbohydrates, which are the substances that then hold more water in the soil.”

Janet advises stopping digging “to preserve the soil structure and mycorrhizal fungi and shade the soil with mulch or non-metallic (which heat up in the sun) border edgings.” Another technique that helps build healthy soils is to use green manures and ground cover plants to maintain good moisture levels.