'Deep watering' is the expert-approved method that will help your plants cope and flourish during the July heatwave

When the temperatures rise, it's tempting to reach for the watering can every evening, and if your garden is looking a little thirsty during these heatwaves, you might assume the answer is to water it every day.

But according to gardening experts, that's one of the biggest watering mistakes you can make, as it could be making your plants less resilient. Instead, they recommend deep watering, which is a simple technique that encourages stronger roots, healthier growth and helps plants cope better with long spells of dry weather.

If you're looking to protect potted plants in a heatwave or wondering how often to water plants in hot weather, changing the way you water rather than simply watering more often can make all the difference. So I asked the pros how I should be keeping my container plants well watered this summer with deep watering.

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What is deep watering?

Deep watering is exactly what it sounds like. Soaking the soil slowly enough for water to reach the roots, rather than just dampening the surface.

'Deep watering is one of the easiest ways to help plants through a hot spell,' says Jo McGarry, luxury garden design expert at Caragh Nurseries. 'Instead of giving them a quick splash every day, it's much better to give them a really good soak every few days. That way, the water gets right down to the roots where it's needed most, rather than just wetting the surface.'

Lucie Bradley, gardening and greenhouse expert at Easy Garden Irrigation, explains that established plants should ideally be watered deeply enough for moisture to reach around 20 to 30cm below the surface. While that sounds like a lot, it's simply about watering more slowly so the soil has time to absorb every drop.

That slow approach is what makes all the difference. While it takes a little longer than giving borders a quick spray with the hose, it encourages roots to grow down into the soil where moisture lasts much longer.

Richard Barker, horticultural expert at LBS Horticulture, explains that light watering from the start encourages roots to stay close to the soil surface, where moisture disappears fastest. Whereas deep watering helps plants develop a much stronger root system that's naturally better equipped to cope with drought.

Why is deep watering better than watering every day?

It may sound counterintuitive, but watering less often can actually produce healthier plants.

'When plants only get a little bit of water at a time, their roots stay close to the top of the soil, which means they dry out much faster when the weather heats up,' says Jo. 'A proper soak encourages the roots to grow deeper, helping plants stay healthier and cope much better with long periods of dry weather.'

Lucie adds that deep watering also reduces evaporation because the water has time to soak into the ground instead of sitting on the surface or evaporating in the midday sun. Better still, deeper roots are less exposed to extreme temperatures, helping plants continue to take up water and nutrients even during hot weather.

Deep watering essentials

How to deep water your plants properly

You don't need to buy any expensive equipment if you don't want to, as a watering can or garden hose works perfectly well, but the trick is to water slowly at the base of the plant.

Lucie says the key is slowing everything down, rather than moving quickly from one plant to the next. She says you should spend a little longer on each one, allowing the water to soak into the soil and adding more.

So instead of spraying lots of water quickly over the soil, reduce the flow and water directly at the base of each plant for several minutes so the moisture has time to penetrate the ground instead of running off.

She also recommends avoiding wetting the leaves wherever possible. Delivering water straight to the soil means less is lost through evaporation and helps reduce the chances of fungal diseases developing on damp foliage.

Richard adds that if you notice water pooling on the surface, stop watering for a moment and allow it to soak in before continuing. If you keep adding water too quickly, it simply runs away instead of reaching the roots.

Once you've finished watering, Jo recommends adding a layer of mulch around your plants. Bark, gravel or even leftover compost (I love RocketGro's Magic Mulch, which you can buy at Amazon) can help lock moisture into the soil, reducing how quickly it dries out during hot weather and meaning you'll need to water less frequently.

If you've got lots of borders or vegetable beds to water, however, specialist irrigation can make life much easier. 'You don't need anything too complicated,' says Jo. 'Soaker hoses like Gruntek porous soaker hose from Amazon, and drip irrigation systems, like Hozelock Easy drip irrigation system available at Amazon, are great if you've got larger beds because they release water slowly and evenly.'

When to deep water plants

Experts recommend you water plants in the morning or at night, when temperatures are cooler, and the water has time to soak deep into the soil before the heat of the day causes it to evaporate.

'If you can, water early in the morning or later in the evening when it's cooler,' says Jo. 'You'll lose less water to evaporation, and your plants will have much more chance to soak it up before the heat of the day kicks in.'

Lucie adds that during the hottest part of the day, more moisture is lost before it reaches the roots, making watering far less effective.

Most established plants will benefit from deep watering during prolonged hot weather, but it's particularly important for newly planted trees, shrubs and perennials that are still establishing their root systems.

Container plants and hanging baskets will also appreciate a thorough soak, although they'll usually need watering more frequently than plants growing in the ground because compost dries out much faster.

So there you have it! By swapping quick daily sprinkles for the occasional deep soak, you'll encourage stronger roots, healthier growth and plants that are much better prepared to cope with hot, dry weather.