Little and Often Is the Biggest Mistake

When the mercury climbs and the ground starts to crack, the instinct is to reach for the watering can every evening and give everything a quick sprinkle. It feels productive, and the plot looks fresher for ten minutes. But this is the single most common watering error on British allotments and in kitchen gardens, and it does real damage over a dry summer.

Frequent light watering only wets the top few centimetres of soil. Roots, being sensible things, grow towards moisture — so you end up training your plants to root shallowly in the exact layer that dries out fastest. The result is crops that wilt at the first hint of sun and need watering constantly. A deep soak every few days does the opposite: it drives water down 20–30cm, encourages deep rooting, and builds genuine drought resilience.

So the golden rule for July and August is simple: water deeply, and less often. Once or twice a week is plenty for established plants in open ground, even in hot weather, provided you do it properly.

How to Water Deeply and Properly

Think in litres, not in passes with the can. As a rough guide, most vegetables want the equivalent of around 20 litres per square metre per week in hot, dry conditions. For individual plants that means roughly:

• Tomatoes, courgettes, cucumbers, squashes: 5–10 litres per plant, twice a week.
• Runner and French beans, sweetcorn: 5 litres per plant per week once flowering.
• Brassicas, leeks, celery: 10 litres per square metre weekly.
• Salad, spinach, radish: 2–3 litres per square metre every two to three days — these are shallow-rooted and genuinely need little and often.
• Containers and grow bags: daily, up to 4–5 litres per tomato plant in a heatwave. Containers cannot be treated like open ground.

Aim the water at the soil around the roots, not over the leaves. Wet foliage invites blight on potatoes and tomatoes and encourages mildew on courgettes. Push a finger into the soil before you water — if it is damp 5cm down, walk away and save the water. And water steadily rather than in one flooding gush, so it soaks in rather than running off down the path.

Mulch: Your Best Ally in a Heatwave

If you do only one thing to protect your plot from drought, mulch. A 5–8cm layer of organic matter over damp soil can cut evaporation by half and keep the root zone several degrees cooler.

• Garden compost or well-rotted manure — ideal around hungry crops like courgettes, beans and brassicas.
• Straw — excellent under strawberries and around tomatoes; keeps fruit clean too.
• Grass clippings — use in thin layers (1–2cm) and let each dry before adding more, or they turn to a slimy mat.
• Leafmould or composted bark — good for fruit bushes and perennial beds.

Always water first, then mulch. Mulching dry soil traps the dryness in. Around thirsty plants, you can also sink a plastic bottle with its base cut off beside the stem and water straight into it — the water goes down to the roots rather than across the surface.

Which Crops to Prioritise When Water Is Short

On a hot week with a hosepipe ban looming, you cannot treat every bed equally. Spend your water where it earns its keep:

• Newly planted and transplanted crops — their roots have not yet spread, so they are entirely dependent on you.
• Flowering and fruiting crops — tomatoes, beans, courgettes, peppers and aubergines drop flowers and set poor fruit if stressed now.
• Leafy crops — lettuce, spinach and chard bolt and turn bitter fast when dry.
• Containers, grow bags and raised beds — they dry out far quicker than open ground.
• Moisture-lovers — celery, celeriac and cucumbers sulk badly without regular water.

Lower priority: established fruit bushes and trees, carrots, parsnips, onions and garlic. These have deep roots and will usually ride out a dry spell, though a good soak at pod or bulb-swelling time still pays. Established herbs such as rosemary, thyme and sage prefer it on the dry side — leave them be.

The Right Time of Day

Early morning is the best time to water. The soil is cool, evaporation is low, and foliage dries quickly as the sun rises, reducing the risk of disease. If mornings are impossible before work, evening is a perfectly good second choice — just avoid soaking foliage, as damp leaves overnight are an open invitation to slugs and fungal problems.

What you should never do is water in the middle of a hot afternoon. You will lose a large share to evaporation, and droplets on leaves can act like tiny lenses and scorch them. If a plant is collapsing at midday, that is often just heat stress rather than true drought — check again at dusk before reaching for the can.

Clever Ways to Stretch Every Drop

Good growers get ruthless about efficiency in a dry summer. A few habits worth adopting:

• Water the soil, not the path. A rose on the can for seedlings, a bare spout for established plants.
• Use a sunken pot or olla. Bury a terracotta pot or purpose-made olla beside courgettes and tomatoes and fill it — water seeps slowly straight to the roots.
• Recycle grey water. Cooling water from boiled vegetables, rinsed salad and even bathwater (using gentle, plant-safe soap) can go on mature ornamental beds and fruit bushes, though not on salads or root crops you eat raw.
• Capture every drop. Water butts filled in spring are worth their weight in gold by August. A tarp or upturned bin lid can funnel surprise showers into a bucket.
• Hoe shallowly, don't dig. A light hoe creates a dust mulch that reduces surface evaporation — just do not go deep enough to damage roots.

Water wisely, mulch generously, and your plot will come through the hottest fortnight of the year in far better shape than you might expect.