Which plants need to be watered while you're away, and which can fend for themselves

Telegraph

24-07-2025

It may have rained in recent days, but much of the country is experiencing a drought and millions of us are in the middle of a hosepipe ban that may go on for months. Rest assured, there's no need to water everything. Ignore the lawn, it will recover once the rain returns, and don't worry about established aromatic and silvery plants either. They have their own built-in sunscreen. Leaf shape matters too. If the foliage is long and linear, like an iris, kniphofia or hemerocallis, or if it's highly divided, like rosemary or dianthus, these plants will survive because transpiration is minimal.
The following plants do need our help though. Most can get by on a thorough twice-a-week soaking in the morning, or in the evening. If you're going away, neighbours are often willing to help. Do encourage them to pick the beans, courgettes and tomatoes, so that they keep on cropping. Recycle as much water as possible, rather than putting it down the plug hole, because it can be tipped on to the garden. Soak the area around the plants. Dribbling water on is worse than no water, because it encourages the roots to surface. Thorough spot watering is the way to go.
The eight essentials
Greenhouse Tomatoes
Every day
The greenhouse is the hottest place in the garden, but applying water-soluble white shading helps to keep it much cooler. It's quick and easy to apply with a brush. Greenhouse tomatoes will need watering daily, preferably in the morning if possible. Keep the water well away from the fruit and foliage, to prevent fungal disease, and ventilate the greenhouse because tomatoes dislike extreme heat.
If you're going away, feed just before you go using a soluble tomato food. This will help to prevent blossom end rot, a stress disease that blackens the underside of the fruit. Irregular watering is often a cause. Greenhouse cucumbers need less water than tomatoes, I find. Overwatering can cause them to wilt. Every other day is the way to go with these – but it does depend on temperature. Outdoor tomatoes also benefit from plenty of water. Move them into an area that gets afternoon sun, if you're going away.
Runner beans
Every couple of days
These come into their own as the days begin to shorten, due to their South American equatorial provenance. Watering them now will help them to crop for the next couple of months, so these are top priority too. Tripods suffer less from drought and wind damage than straight lines of beans. Choosing the correct varieties also helps. Hybrid runner x French beans, such as 'Moonlight' and 'Firestorm', are able to crop heavily in drier, hotter conditions. They won't shed their flowers on hot nights, when temperatures go above 16C, but this is a real problem with traditional runner beans. Gently watering them every couple of days is the way to go.
The following vegetables can be left to their own devices. Carrots and beetroot have fleshy moisture-seeking roots and brassicas have leathery foliage, so they'll be fine. Onions and shallots should be ripening now, rather than growing.
Newly planted roses
Twice a week or more
These are very vulnerable in their first growing season, because most have been potted up in the spring, so their fibrous root system hasn't fully developed. Gently tipping a whole can of water round the base, a couple of times a week, is vital. If you're away, make sure your helpers know where your new rose is. Once roses are established, they are very tolerant of dry conditions and heat. Check newly planted clematis as well. The smaller-flowered viticellas are the most drought-tolerant ones, once established.
Hydrangeas
Twice a week
Hydrangeas have suffered this year due to the unusually dry spring and many are still struggling. They include the shade-loving, fairly drought tolerant forms of Hydrangea paniculata such as 'Limelight' and 'Kyushu'. Keep all your hydrangeas hydrated with a twice weekly bucket, or can of water, otherwise you may lose them.
Trees and woody shrubs planted in the last two years
As required
Keep an eye on these, because these are expensive items to replace. This year the ground has been so dry that the roots will not have penetrated into the surrounding soil, so watering may well be needed. When a tree, or shrub, is in distress the foliage tries to avoid transpiration in two ways. Sometimes the plant slants the leaves straight down and witch hazels, or hamamelis, often do this. Watch their foliage carefully. If the leaves turn to the vertical, this winter-flowering gem is water-stressed and you may lose it.
Other woody plants close their leaves up. Both are distress signals, indicating that this tree or shrub needs water now. If the worst happens, and the foliage browns and drops, don't be too hasty to remove it. Woody plants can (and do) re-shoot next spring, but it's best not to put that one to the test.
Geums and astrantias
Twice a week
These both flower in May, and both hate dry conditions so it's imperative to water them throughout dry summers. Otherwise, both will fade away and die. Red and dark-pink astrantias are generally more demanding on the moisture front. However, this year they've all suffered – even the normally drought-tolerant pale-pink 'Buckland' has shrivelled here. Flagging phloxes need our help too. If they've turned brown, cut the stems back and water to encourage regrowth.
Shade-loving South American late-summer tender plants
Every other day
Fuchsias, impatiens and begonias stay vivid and colourful late into the year, so you don't want to lose them in summer. They thrive in cooler semi-shade and moist soil, so these will also need watering. If you're going away, move them into full shade and stand them in pot saucers. Even then, they will still need watering every other day when it's dry.
Potted plants are always vulnerable, especially smaller potfuls. It's a good idea to use larger containers. The sun lovers, such as pelargoniums, could be left for a week, but not two. 'Pink Capricorn' is my star recommendation. It will get by on a weekly water if it has to.
Later season perennials
Three times a week
They've caught the worst of the summer drought, but most will recover once the autumn rains come. The only three I'd specify, for resuscitation purposes, are echinaceas, heleniums and rudbeckias because a dry, hot spell can see them off. A three-times-weekly can or bucket, gently tipped over them in the morning or evening, will keep them going for another year.