Why it pays to use less mains water

Our gardens are getting thirstier. Warmer, drier summers are becoming more common, hosepipe bans now arrive most years in some regions, and yet the average garden still soaks up a surprising amount of treated drinking water. A hosepipe left running for an hour can shift well over 1,000 litres — roughly what a family of four gets through in a couple of days. That is beautifully clean, carefully treated water, poured onto a flowerbed.

The encouraging news is that most gardens can thrive on a fraction of it. With a bit of planning, a few simple habits and a slightly different eye when you are choosing plants, you can cut your reliance on the tap dramatically — and your plants will often look better for it.

Harvest the rain you already get

Even in a dry-looking summer, your roof collects an extraordinary amount of water. As a rough rule of thumb, every square metre of roof yields about one litre for each millimetre of rain. So a modest 10 square metre shed roof will send around 10 litres into your water butt after just 1mm of drizzle, and a decent downpour can fill a 200-litre butt in no time.

• Fit a diverter to a downpipe so rain is captured before it disappears into the drain. Most kits are inexpensive and simple to install.
• Site butts on firm, level ground. A full 200-litre butt weighs well over 200kg, so a wobbly paving slab is not the place for it.
• Link two or more butts together with a connector kit — the second fills once the first is full, doubling your storage for very little cost.
• Keep a lid on. It stops leaves and algae, keeps the water clean, and makes the butt safe around children, pets and visiting wildlife.
• Consider a slimline butt for a narrow passage or beside a greenhouse, where a round one simply will not fit.

Rainwater is also better for plants than tap water — it is soft, free of the chlorine and lime that can leave marks on leaves, and ideal for blueberries, camellias and rhododendrons.

Mulch: the simplest water saver of all

Bare soil bakes dry in the sun. Cover it and you can cut evaporation from the surface by a third or more, while smothering the weeds that quietly compete for every drop.

Spread a 5–7cm layer of organic mulch over damp soil in spring, and top it up again in autumn. Bark chippings, leafmould, garden compost, well-rotted manure and spent mushroom compost all do the job, and each feeds the soil life beneath as it breaks down. Keep the mulch a hand's width clear of stems and tree trunks to avoid rotting the bark, and never pile it up against a plant like a cone.

Containers benefit too. A layer of gravel, pebbles or even broken slate on top of the compost slows evaporation and sets off the planting nicely.

Water at the right time and in the right place

Timing matters as much as quantity. Water early in the morning, when the soil is cool and there is time for moisture to soak down before the sun climbs, or in the evening, when it will sit in the soil overnight rather than vanishing into the air. On a hot day, mid-afternoon watering is largely wasted.

Aim for the soil, not the foliage. A watering can with the rose turned low, or a seep hose laid along a border, delivers water straight to the roots where it is needed. Wet leaves, by contrast, invite mildew and scorch in strong sun.

Then water deeply and less often. A thorough soak twice a week builds deep, resilient roots; a light daily sprinkle only wets the top centimetre and encourages plants to root shallowly, making them more vulnerable when you go away. Push a finger 5cm into the soil — if it feels damp, leave the can where it is.

Give your attention to new plantings, containers, vegetables and fruit first. Lawns can be left to go golden; most British lawns green up again within weeks of the autumn rains returning.

Choose plants that cope with dry spells

Right plant, right place saves more water than any gadget. Group moisture-lovers together in the shadiest, dampest corner of the garden, and let the sunny, free-draining spots host plants that genuinely enjoy them — rosemary, thyme, sage, lavender, sedum, eryngium, cistus, salvia and hardy geraniums all shrug off a dry spell.

Improving your soil helps enormously too. Digging in plenty of organic matter gives sandy soil the ability to hold water and helps heavy clay drain and root more freely, so every drop you add goes further. In containers, use larger pots where you can — they dry out far more slowly than small ones — and cluster them together in light shade during hot weather.

Small habits that add up

• Reuse greywater from rinsing vegetables or a cooled bath on established ornamental beds. Avoid it on salads and herbs you will eat raw, and go easy on acid-loving plants.
• Sink a plastic bottle with a few holes pierced in it, neck down, beside thirsty crops such as courgettes and tomatoes. Fill it and the water reaches the roots directly.
• Fix drips and leaks in hoses and outdoor taps — a slow drip wastes more than you would think over a season.
• Keep a shallow dish of water with a few pebbles for birds, hedgehogs and bees. Top it up in hot spells and you are helping wildlife as well as your borders.
• Wait before you water. A surprising number of plants recover from a warm afternoon by evening. Check first, then water properly if they still need it.

None of this requires much effort or expense, and together these habits can cut your garden's thirst by half or more. Your plants will be healthier, your soil richer, and your water bill quietly grateful.