Why harvesting rainwater is worth the effort

There is something quietly satisfying about watching a summer shower fill a water butt rather than vanish down the drain. For British gardeners, harvesting rainwater is no longer just a niche hobby. With hosepipe bans arriving in many regions during dry spells, having a stored supply means you can keep containers, young trees and prized borders alive without reaching for the tap. A modest 20 square metre roof can capture over 1,000 litres from just 50mm of rain, which is more than enough to make a real difference. Rainwater is also better for plants than tap water, being soft and free from the chlorine and fluorides that can build up in potting compost over time.

Setting up water butts and downpipe diverters

The simplest system starts with a single water butt placed under a downpipe. You can buy kits that include a diverter, which fits into the downpipe and sends water into the butt while allowing the pipe to keep flowing during heavy rain. Position the butt on a firm, level base, ideally on a stand or blocks, so you can fill a watering can easily. If you have room, link two or more butts together with a connector pipe so the first one overflows into the next. Fit a fine mesh filter or a leaf catcher at the inlet to keep out debris and mosquito larvae. An overflow pipe should lead to a soakaway, a rain garden, or a thirsty border, so surplus water goes back into the ground rather than flooding your patio.

• Use a downpipe diverter rather than cutting the pipe completely, so you can redirect flow in winter.
• Raise the butt by at least 30cm to give good pressure for a hose or drip line.
• Link butts in series to increase storage without extra downpipes.
• Check local rules: in some areas, you may need permission to alter a shared downpipe.

Mulch: the quiet hero of moisture retention

Harvesting water is only half the story. If your soil dries out as fast as you water it, you are simply feeding the sun. A generous layer of mulch acts like a blanket, slowing evaporation and keeping the soil cool. Aim for 5–7cm of organic matter, spread over damp soil in spring or autumn. Do not pile mulch against stems or trunks, as this can cause rot. Leave a small gap around each plant. In borders, bark chippings, composted bark, or leaf mould work beautifully. For Mediterranean plantings, a gravel mulch looks sharp and reflects heat. Even a thin layer of grass clippings, applied in stages, can help, though avoid thick, smelly mats.

Choosing drought-tolerant plants that ask less of your water butt

The right plant in the right place is the easiest way to reduce demand. Many classic British garden favourites are surprisingly thirsty, but there is a rich palette of drought-tolerant plants that thrive in full sun and well-drained soil. Lavender, rosemary, thyme, and oregano are obvious choices, but consider also sedum, eryngium, cistus, perovskia, and ornamental grasses such as stipa and miscanthus. Verbena, nepeta, and echinops add colour and attract pollinators. Group thirstier plants together in one bed so you can water them efficiently, and keep the rest of the garden on a leaner regime. Once established, these plants need little more than the occasional deep soak during prolonged dry spells.

Watering wisely: habits that stretch every drop

How you water matters as much as how much you store. A quick daily sprinkle encourages shallow roots and wastes water through evaporation. Instead, water deeply and less often, aiming for the root zone rather than the leaves. Early morning or late evening is best, when the sun is low and the air is cooler. A watering can delivers water precisely, but a drip irrigation line or soaker hose connected to a butt on a stand can save time and effort. You can also bury unglazed terracotta pots, called ollas, near thirsty plants, filling them weekly so water seeps slowly into the soil. Check the soil before watering by pushing your finger in to the second knuckle. If it is damp, wait another day. Reusing greywater from washing up or rinsing vegetables is fine for ornamentals, provided you use a gentle, plant-safe soap.

Keeping your system sweet and looking ahead

A little maintenance keeps your harvesting setup working for years. Clean filters and gutters each autumn to prevent blockages, and check that overflows are clear before winter. In cold snaps, drain exposed pipes and taps to avoid splits, but leave the butt itself part-full to resist frost damage. If you have space, add a second butt or a larger tank before next summer. You might also consider a simple rain gauge to see how much you are actually capturing. Every drop you store is a drop you do not take from the mains, and every mulch layer and drought-tolerant plant makes your garden more resilient. Start small, build gradually, and you will be surprised how much difference a few simple changes make.