How Smart Gardeners Prepare for a Heatwave

A heatwave can seriously set back or even kill your plants. But get your garden prepared with the tips I’m about to share, and yours can be the garden that thrives through even blisteringly hot summers...

Water Effectively

Let’s start with making the most efficient use of precious water, which should save a lot of time too.

The first thing to do before even reaching for the watering can or hose is to check how moist the soil actually is. On the surface the soil might look dry, but scratch beneath the surface to see what’s really going on. Soil that looks dust-dry on top may actually be moist an inch or two below, where the roots are – so check conditions before watering as it may just save you a job.

The best time to water is first thing morning, so plants can load up with water ahead of the heat of the day. Early watering also gives foliage time to dry off before nightfall, so there are fewer opportunities for slugs that come out to feed at night. Warm, humid conditions overnight can also be a breeding ground for disease, particularly fungal diseases like blight, so allowing foliage a chance to dry off is a wise play.

But if you can’t water first thing in the morning, just water whenever you can, because it’s better than leaving plants struggling.

Speed Up Watering

Watering gives us an opportunity to inspect plants for pests, diseases or – in hot weather – the tell-tell signs of heat stress as we move through the garden. But I’ll be honest, watering can get a little bit tedious if you’re having to water more often than you’d wish during a heatwave!

Up until a few years ago I mainly watered the garden by hose. But on a hot day, when water demand is high and water pressure drops, the flow rate could be frustratingly weak. Even at the best of times, it isn’t fast.

So let me introduce you to my workaround for this, which combines the convenience of a hosepipe with the speed of a watering can. When my water barrels are empty, I now drop the hosepipe into it, turn it on, and let the barrel fill up to the top (keeping an eye on it so it doesn’t overflow of course). Once it’s full, I can go ahead and dip in my watering can and apply the water far more quickly than watering directly by hose. I estimate the flow rate from a watering can, even with the rose on, is at least three times quicker than the hosepipe.

To make the most of each trip to and from the barrel I double up, using two watering cans. This means I can deliver two lots of water at once, with a watering can in each hand.

The ultimate solution would be automatic irrigation of course, delivered by ground-level soaker hoses or drip irrigation to minimize waste and get the water right down to the roots. It’s something I’m considering, but for now my two-can ‘dunk and deliver’ system is working well, and it means I still get to check on my plants as I go.

Mulch to Conserve Soil Moisture

A dry spell is hard on plants, but a hot, dry spell is even worse. Heatwaves ramp up the speed that moisture evaporates from already under-strain soils. And bone-dry soils then heat up even quicker – it’s a vicious cycle.

One of the easiest ways to protect against this effect is by mulching. Mulches are simply materials spread over the soil surface to suppress weeds and, crucially, help retain moisture. The best mulches consist of organic, biodegradable materials like grass clippings, wood chips or straw, which have the bonus of rotting down over time and improving the soil too.

Water before muching so we’re covering moist soil. The beauty of mulch is that it shades the soil, which not only reduce evaporation from the soil surface, but keeps roots cooler too, so plants will be under a lot less stress. You can reapply mulches whenever they’ve rotted down.

I like to use grass clippings, applied thinly, but straw is another go-to mulch. It’s particularly useful if you don’t have a lawn to get grass clippings from, or if your grass has simply stopped growing due to lack of water during a prolonged hot and dry spell. I use straw around bigger plants like squash or tomatoes, and have had great success using straw as a mulch for potatoes.

Chunkier mulches like wood chips or bark are great around fruit bushes, trees and any other large plants – anything that isn’t bothered by slugs. They rot down a lot slower, so in most areas you should only need to mulch once to keep plants happy for an entire year. As the mulch becomes part of the soil over time, it adds organic matter which improve the soil’s structure and water-holding capacity. It’s a lifesaver around my fruit bushes.

Cast Some Shade

Most plants prefer full sun, but in really hot conditions shade is most definitely your friend! So if you endure hot summers every year, grow your greens and other cool-season crops like salads in the cool shade of taller, more heat-tolerant crops, or by setting up shade cloth or similar. A simple framework over which you can throw some sort of shade cloth to help the likes of spinach and lettuce keep their cool works well. Think about how you might shade heat-vulnerable crops during a heatwave and, if you can, be on hand to rig up temporary protection from the worst of the sun, especially during the hottest part of the day from midday to mid-afternoon.

It's worth grouping containers together so they can shade each other. This will help humidity to stay higher and keep conditions a bit cooler at the roots, slowing water loss.

Container Watering Solutions

And on that note, let’s look at a few ideas for saving time when watering containers. They’re not as comprehensive as an irrigation system but offer a low-tech get-around that helps me extend the periods between waterings.

At the most basic end of the scale is the trusty old pot saucer. Put your pot into the saucer then water from above as normal. Now water that would otherwise drain through and away can collect in the saucer, enabling it to be absorbed back up into the potting mix. This very simple step makes all the difference in hot or dry weather, not only saving water but helping to moisten the potting mix more thoroughly too.

Low-Tech Drip Irrigation

The next step up is terra cotta watering spikes. All you have to do is push the watering spike into the potting mix, fill up a glass bottle with water, then flip it over into the watering spike. Terra cotta is porous, so the watering spike will become saturated with water before slowly seeping moisture out into the potting mix. The best bit is that the spike holds onto the water until the potting mix surrounding it is dry, so the moisture is being released as and when plants really need it.

You can use watering spikes for plants in the ground too, but I have an even better idea! Seal the bottom of a terra cotta pot to trap water when it’s filled. Place a saucer on top to keep the water cool and stops any unfortunate creatures from wandering in and drowning. Like the watering spikes, the terra cotta will release water as your plants need it. Again, this saves a little time watering, which is invaluable in a heatwave. If you’d like to learn more about simple, low-tech but effective self-watering solutions like this, check out this video.

Keep your cool this summer and keep your plants happy too! And if you are looking to add irrigation to your garden ahead of the heat, you can always plan your setup – everything from tubing to connectors – using our Garden Planner’s irrigation planning feature. If you haven’t started your completely free, no-obligation trial yet, put that right by clicking here.