Watering Plants in Hot Weather

Watering plants in hot weather has Gardening Teacher Tips and Ideas for which plants you should prioritise when there is a shortage of water. Whether that’s because of hot weather, a drought situation, and possibly hosepipe bans, it is becoming more crucial for gardeners to know when and how to conserve water in their gardens. And not forgetting that it’s important to use your gardening time wisely too!

Why do we need to conserve water?

Look at it this way –

Plants take up their nutrients through their roots as a “drink”, by using the soil water. Therefore, if the soil dries out, your plants will starve (wilt).
The average amount for vegetables and flowers is about an inch of water per week. Doesn’t sound a lot, does it? But if you spread that inch of water out over the 10 x 10 foot space that is your vegetable plot, it comes to about 62 gallons!
Water is a finite resource, and we should all bear that in mind. Do you remember the water, or hydrological cycle from school?

There are four main stages to how the water goes round – evaporation, condensation, precipitation and collection. If there’s not enough precipitation and too much evaporation then the collected water levels, in lakes, reservoirs, streams and the soil are not sufficient to keep plants and animals (including us) alive.

Watering Plants in Hot Weather

Whether you want to conserve water because you have a water meter, because there’s a hosepipe ban, or because you think it’s a sensible thing to do, which are the easiest ways to do so in the garden?

Collect and store rainwater

Rain is better for ponds with fish and wildlife as well as for plants. When the stored rainwater is running low, I prioritise fish and wildlife ponds over plants. And ensuring that there are shallow areas means its safe for birds to drink from too.

Water butts are the obvious containers, collecting water from your gutters and downpipes. Where the space is narrow, try two smaller ones joined together to maximise storage. If you’re not able to lift watering cans, water butts can be used with a hose attachment. This would be excluded from a hosepipe ban as you’re not using mains water. Some gardeners have water tanks: remember to put a lid on them to reduce evaporation. (Which also prevents cats and other animals from falling in and drowning)

Other water sources for watering plants in hot weather may include –

Paddling pools

Don’t just tip it out, re-use the water. Yes, a bit of an effort, so why not get the children to join in? NB if you’ve used an additive to keep the water clean, it may not be suitable for plants. You could still use it for washing the car windows and lights though (the bits you do need to keep clean for safety reasons).

Other ‘greywater’

Water that’s been used to rinse fruit and vegetables is generally fine to use.
Whether you can use water that you’ve washed your hands or dishes in depends on the soap (eg nothing anti-bacterial) Only use it on ornamental plants and as a short term measure.
There are other areas where you can reuse water, for example from the bath, but it begins to get complicated.
To use grey water long term in the garden you’ll probably need a full grey water system.

Avoid irrigating plants that don’t really need it. Many plants receive too much water and that can be as bad for them as too little.

Lawns

I exclude this from watering unless it’s recently laid turf or sown seed. Grass is a great survivor and will green up with the first rainfall we have. The leaves, or turf, that you see may die, but the roots have gone dormant, to conserve water and energy. Which is why it can put out new leaves so quickly when it rains or the temperature cools.

Trees and Shrubs

Established / mature ornamental trees and shrubs –

These should have a root system that goes deep into the soil, so they shouldn’t need watering unless we have a sustained drought (high temperatures and no rain for more than 4 weeks). Up to a point they may manage their water needs themselves, for example by dropping leaves and even branches.

Young and recently planted ornamental trees and shrubs –

These will need extra water in the first 3 -5 years after planting, depending on the species and size at planting.

Edible trees and shrubs-

Although they need less water generally once established, ie 5 years or older, fruit trees and bushes will still need water at certain key times. This is at bud set, pollination, fruit set, about 4 weeks and 2 weeks before you expect the fruit to be ripe, and just before harvest.

You can buy aids to make it easier for you to that ensure trees are getting enough water –

Tree bags It’s best to add these when you first plant trees and shrubs, although you can add them retrospectively.
Simple drip hose surrounding the tree, linked to a reservoir, eg a small water butt. This is even better if it can be set up when planting so watering is at root depth.
Watering funnels that sit in the ground, (similar to those seen for watering tomatoes in the greenhouse)

And it is possible to make your own mini reservoirs by upcycling other products such as empty lemonade bottles.

The vegetable garden and kitchen garden

Your priority for watering plants in hot weather will most definitely include the plants here! They will need water and quite a bit if your crops are heading towards harvest.

Gardening Teacher Tip for the Kitchen Garden

Strip off leaves from mature tomato plants as they lose a lot of water through their leaves. By removing much or most of the foliage, the water goes to ripening those green tomatoes instead.

Herbaceous perennials, small perennials

Many established herbaceous perennials will also be fine without extra watering unless we are in more of a sustained drought situation. Although heavy pruning of plants you want to keep is not advisable in a prolonged drought as it adds stress, keep up with deadheading and cut the stems a little shorter than you normally would. This reduces the plant’s need for water and watering.

How often should you be watering plants in hot weather?

Water heavily and infrequently, not lightly and infrequently, or even lightly and frequently. Water is for the plants’ root system, not for the leaves or flowers.

If you’ve planted the right plants in the right place and they’re growing in good soil, they will have developed the ability to withstand all sorts of heat, frost and other traumas. As an example, in my previous, well-established garden, I only watered mature planting about 3 times a year.

The garden was sheltered and many of the Mediterranean type shrubs grew happily with little attention. For example: –

Lavender
Rosemary
Salvia
Oleander
Jasmine

Of course, the fruit and vegetables, particularly the annual types, needed more watering. As did summer pelargoniums and other plants that were in pots.

Pots

To reduce watering needs generally, place pots on trays or saucers so that water run off can be accessed by the roots later. However, do be aware that not all plants like their roots sitting in water for any length of time. These will fare better sitting on a layer of damp gravel. If you need to buy gravel, why not let the children choose which one? There will be a selection of colours, white, caramel, grey for example. Or you could let them head for colourful aquarium gravel which works just as well!

NB plants in raised beds will generally dry out more quickly than those in the ground. They are effectively very large pots.

Shade vs sun

Plants with grey foliage such as Lavender or furry leaves like Stachys byzantina, tend to be more drought tolerant, but when the temperature rises, most plants benefit from shade at midday.

When is the best time to be watering plants in hot weather?

As to when in the day you should water, the best time is between 4 – 9am to avoid or at least minimise evaporation. If that’s not possible (and it isn’t always) then water in the late afternoon or early evening. You’ll get some evaporation, but the foliage shouldn’t be too wet overnight which can cause issues with disease and slugs.

Remember –

Check the soil moisture at root level: if it’s cool and damp, the plant is fine.
Aim water at the base of your plants, ie on the soil.

What else can you do to keep your plants healthy in hot weather?

Mulching the soil after a thorough watering will reduce evaporation regardless of the time of year. It also helps to prevent a hard pan forming on the soil surface, which will seriously reduce ir even prevent any water penetrating down to where its needed by the plants.

Gardening Teacher Tip

When you’re buying bags of mulch, a rough guide for the amount you’ll need is that the contents will cover the ground to 2 to 3 times the size of the bag.

And finally

Watering plants in hot weather should not normally be much more onerous a task than watering your garden normally is. It’s only those unfortunate gardeners who for various reasons have most of their garden growing in pots who are getting the extra exercise.

And yes, I’m currently one of them. I moved in with at least four transit van loads of plants in pots from my previous garden. There were no borders for the plants to be dug into the ground until space had been cleared and prepared. And of course, by then the ground was rock hard as we hadn’t had rain for weeks. Yes, I could have soaked the borders but the 62 gallons we mentioned near the beginning wouldn’t be anywhere near enough to soak down to root level! No, its better for the water supply, the soil and for my plants to keep them in pots until we start getting rain. I’ll let you know how I get on – my Moving Gardens tips are in the link below and some of the Instagram posts are from this garden.

And for further gardening advice and inspiration, check out Plews Potting Shed blogs, including the selection below and our monthly Tipsheet – You could come and find us on Instagram Pinterest and Facebook too.