Watering the Right Way

Deep, early and less often than you think

4 minBeginnerUpdated 2026-10-23 Watering the Right Way

You will learn

Judge when a bed actually needs water
Water deeply so roots grow down, not up
Spot overwatering and underwatering by the leaves

⚠️ Keep water butts covered and away from small children. Do not drink collected rainwater without proper treatment.

How much and how often

Most vegetables need about 25 mm of water a week in mild weather and up to 50 mm in hot, windy weather. That is 25 litres per square metre. It is far better to give that in one or two deep soaks than a light sprinkle every day. Light watering wets only the top 2 cm, roots stay shallow, and the plant wilts the moment you miss a day. A deep soak reaches 20 to 30 cm and roots follow it down, where soil stays moist longer. Check with your finger: if the soil is dry 3 to 5 cm down, water. If it is damp, wait, whatever the surface looks like.

💡 Put a straight-sided tin in the bed. When it holds 25 mm after your watering, you have done a week's worth.

When to water

Water early in the morning. Leaves dry fast, less evaporates, and plants go into the heat of the day fully stocked. Evening watering is second best but leaves foliage wet overnight, which invites mildew and slugs. Never water in the middle of a hot day: up to half evaporates before it reaches the roots. Water the soil, not the plant. Aim the can or hose at the base and keep the leaves dry, especially on tomatoes, courgettes and cucumbers, which get fungal diseases from wet foliage. A watering can with the rose removed lets you place water exactly where it is needed.

Reading the plant

Wilting at 3 pm on a hot day is normal for squash and cucumbers; they recover by evening. Wilting at 8 am means the plant is thirsty. Drooping yellow lower leaves plus soggy soil means overwatering, which drowns roots by pushing out air. Overwatering kills more container plants than drought. Blossom end rot, a black patch on the bottom of tomatoes, comes from uneven watering, not a disease. Cracked tomatoes and split carrots come from a big drink after a dry spell. Consistency is the goal: moist, not wet, not dry. Mulch makes that easy.

Which crops need more

Not everything is equally thirsty. High need: lettuce, celery, cucumbers, courgettes, brassicas and anything in a pot. Medium: tomatoes, peppers, beans, beetroot and chard. Low once established: rosemary, thyme, garlic, onions, sweetcorn and most fruit trees. Timing matters too. Peas and beans need most water when flowering and podding. Potatoes when tubers form after flowering. Tomatoes evenly all season, then slightly less as fruit ripens to concentrate flavour. Onions and garlic want water withheld for the last 2 weeks so they cure in the ground. Seedlings and transplants always need daily attention until rooted.

Saving water

A water butt on a downpipe collects thousands of litres a year for free and rainwater is better than tap for most plants. Cover the butt to keep mosquitoes out. Group thirsty crops together so you water one area, not the whole plot. Grow drought-tolerant crops in the driest spot. Sink a plastic bottle with holes, neck down, beside each tomato or squash and fill it: water goes straight to the roots. Weed regularly because weeds drink too. And mulch. A 5 cm layer of straw or compost halves water loss from the surface. The next lesson covers mulch and drip irrigation in detail.

Check yourself

Which is better for established vegetables?

Deep watering sends roots downward into soil that stays moist, making plants far more resilient.

What is the best time of day to water?

Morning watering loses least to evaporation and leaves foliage dry by night, reducing disease.

A black sunken patch on the bottom of a tomato is usually caused by:

Blossom end rot is a calcium delivery problem caused by irregular water, and steady watering with mulch prevents it.

Yellow lower leaves and soggy soil most likely mean:

Waterlogged soil has no air and roots suffocate, which shows first as yellowing at the base.

Try it for real: Measure a real week of watering

Place a straight-sided tin in your bed or among your pots
Water deeply once, in the morning, and note how long it takes to reach 25 mm in the tin
Each day for a week do the finger test 3 to 5 cm down before deciding to water
Record how many days the bed stayed moist after the deep soak