8 dos and don'ts of watering plants in the heat

Experts debunk the myth that watering plants during the day is a mistake plus more ways to help your garden survive a hot summer

Watering plants with a watering can during hot weather
(Image credit: Klaus Vedfelt / Getty)

Knowing how to water plants in full sun is key to their survival in the heat. With summer temperatures reaching record levels yet again, it can be hard to know how to keep plants alive. Of course, watering them more is the obvious first step, but there is a chance that you're going about it all wrong for optimum hydration.

The best garden hose will go a long way to ensuring correct watering (more on that below). But there's a little know-how to watering plants when temperatures are truly scorching. Gardening experts share their top tips and dispel some of the common myths about watering. 

1. Do water deep into the ground

Your plants have a better chance of surviving a heatwave if they've been watered thoroughly and correctly - that involves watering deep into the ground. Henry Bartlam, the founder of Dig, explains that 'water on leaves is more likely to evaporate than it is to trickle down to the base of the plant, especially on a hot day.'

In the case of trees, however, it can be good to water the bottom half of their trunks as well as into the ground, to aid hydration. 

2. Do use a watering can or a shower hose attachment

Since you don't want to be wasting water splashing off of leaves, using a watering can be a good solution during a heatwave. Batlam says that 'using a watering can, rather than a hose, can save a huge amount of water as it focuses your watering and reduces any risk of superfluous spraying.

'If you do use a hose (and of course, in many cases, hoses are completely necessary) make sure to use an attachment that allows you to stop the flow of water. Plus use a much more efficient shower function rather than a dramatic torrent. Better for the plants, better for your water bill.'

3. Do water plants in the morning if you can

That thing you've heard about never watering your plants during lunchtime because the sun will scorch the leaves? That's actually a myth - the sun isn't nearly strong enough to do that, even on the hottest day of the year. However, there's a different reason why you should try to water plants in the morning. Bartlam says that 'this helps to ensure that as much of the water as possible stays in the ground and on the roots of your plants. The hotter the weather, the more water will evaporate and become useless.'

You can still water plants in the middle of the day, it just won't be as efficient. 

4. Don't water after dark 

Watering after dark, on the other hand, can be bad for plants as it encourages pests, especially slugs, and fungal infections. If you don't have too much garden pest control to think about in your area, watering later on in the day should be safe enough.

5. Don’t give your plants a daily light sprinkling of water

It's better to give them a good soak every couple of days (especially in warmer weather) than a quick splash every day. There is no precise science to this, but if the soil looks nice and damp, and doesn’t dry out quickly, you’ve probably done a good job. 

6. Don't overwater the grass

It can be tempting to soak the grass in your lawn as much as possible, but you should resist this temptation. According to gardening experts at Marshall's, 'Overwatering grass can lead to its demise and therefore grass should be watered during the cooler time periods and only once a week. When watering grass you are looking to water deeply to ensure there’s enough water to see through a drought.'

Oh, and don't get the lawn mower out until it's cooler, either. 

7. Don't ignore the warning signs of dryness

While some full sun plants can bounce back from a bit of neglect and underwatering, others will die quickly, especially water-intensive varieties like hydrangeas, or young plants that haven't established a resilient root system yet. These are the signs that your plants need attention immediately:

  • Sun spots
  • Frazzled appearance/wilting leaves
  • Dry top soil

'The good news is that, if you notice any of these things, you can usually bring the plant back to full health. Plants are generally resilient, and the more time you spend tending them the more you’ll get accustomed to knowing what they’re after, and when.'

8. Do get a water butt

A water butt or rain barrel is 'not necessarily the first priority people think of when planning out their garden, but the amount of rainwater that can be harnessed for plants using a butt will surprise you. If you can, it’s a great investment. There are even get some pretty trendy ones nowadays.' It's a great way to save water and enhance your eco-friendly efforts around the home!

When to water tomato plants during a heatwave?

The answer is: often and whenever they need it! Tomatoes are thirsty plants, especially during fruiting, so you need to give them extra water during hot spells and heatwaves. Watering twice a day is often neccessary, and you can water in the morning and afternoon, or morning and evening. 

Anna is a professional writer with many years of experience. She has a passion for contemporary home decor and gardening. She covers a range of topics, from practical advice to interior and garden design.