Vivid Ready

Water deeply and rarely, at the base, in the morning, and mulch everything. A light daily sprinkle trains roots to stay at the surface, which is exactly what kills a plant when the water stops.

Britain is not thought of as a dry country and gardens here still fail from drought, because rain does not arrive when crops need it and because most watering habits actively make plants less able to cope.

This page matters more in the scenario this app describes than in an ordinary summer, because mains water is one of the first things to become uncertain and a garden is a large consumer of it.

Deep and rare, not little and often

The single most important idea here, and most people do the opposite.

A light watering every evening wets the top few centimetres. Roots grow where the water is, so they stay near the surface. The plant becomes entirely dependent on you continuing, and the surface is the part that dries first and fastest.

A thorough soak twice a week wets the soil to depth. Roots follow it down. A deep-rooted plant finds its own water and survives a dry fortnight without help.

Soak properly. Aim for the equivalent of a good rainfall, which is more than most people apply. Dig down afterwards and check it has actually reached below the surface.
Then leave it. Let the surface dry between waterings.
Established plants in the ground want this. Containers are the exception and genuinely do need frequent watering, because there is nowhere for roots to go.

When it actually matters

Not all thirst is equal, and knowing the critical periods lets a limited supply go a long way.

When water changes the yield

Crop	Critical period
Potatoes	When tubers are forming, around flowering
Peas and beans	Flowering and pod set
Tomatoes	Steadily once fruit sets. Irregular watering splits fruit and causes blossom end rot
Squash and courgette	Flowering and fruit swelling
Onions and garlic	Bulb formation. Stop once they start to ripen
Salad and leafy crops	Continuously. They bolt if checked
Carrots and roots	Steady. Irregular watering splits them
Brassicas	At transplanting, then fairly tolerant
Fruit trees	First two years. After that, mostly not

Newly planted anything is the top priority, always. A transplant has no root system and a fortnight of establishment decides whether it lives.

Established deep-rooted crops can be left. Potatoes, brassicas, roots and anything mature will wait through a dry spell and recover. They may yield less, and they will not die.

Consistency matters as much as quantity for tomatoes, carrots and courgettes. A drought followed by a flood splits fruit and roots and causes blossom end rot, which is a calcium transport problem caused by irregular water rather than by a lack of calcium.

How to apply it

At the base, on the soil, never over the leaves. Wet foliage spreads fungal disease, especially on potatoes and tomatoes, and most of what lands on a leaf evaporates.
Early morning is best. Cool, low evaporation, and the foliage dries during the day. Evening is the second choice and leaves things damp overnight, which suits slugs.
Never the middle of a hot day, when a large share evaporates before it does anything.
Slowly. Water applied fast runs off, especially on dry or compacted soil. A hard-baked surface repels water.
Sink a reservoir. A plant pot, a cut-off bottle upside down, or a length of pipe pushed into the soil beside a thirsty plant, filled instead of watering the surface, delivers water straight to the root zone with nothing lost.
Water the plant, not the bed. In a dry spell, targeted watering of what needs it beats sprinkling everything.
A watering can beats a hose for control, and a hose beats a sprinkler, which is the most wasteful method there is.

Mulch

The highest-value thing on this page after the deep-watering habit, and it is largely free.

A layer of organic matter on the soil surface reduces evaporation substantially, moderates soil temperature, suppresses weeds that compete for water, and feeds the soil as it breaks down.

Compost, a few centimetres, which is the best because it does everything.
Straw, excellent around potatoes, squash and soft fruit.
Grass clippings, in thin layers so they do not go slimy.
Cardboard, under other mulch, on paths and around fruit.
Leaf mould. See soil and compost.

Mulch after watering, onto damp soil, never onto dry. Mulch on dry soil keeps rain out as effectively as it keeps moisture in.

Keep it off the stems, particularly of trees and shrubs, where it causes rot.

Bare soil is the enemy. It dries, crusts, erodes and loses structure. Something should always be covering it: a crop, a mulch or a green manure.

Collecting and storing water

The supply side, and it is where the real resilience is.

Water butts on every downpipe. A roof produces far more water than people expect, and it is free, soft and better for plants than tap water.
Link butts together so overflow fills the next rather than running to the drain.
Size it up. One butt is a few days of summer watering. Several, or an IBC tank, is a season's buffer.
Cover them. Light causes algae, and open water breeds mosquitoes. See mosquitoes and the water store.
The full design is on size and build a rainwater system, which covers roof area, yield calculations and first-flush diversion.

Rainwater for the garden is easy. Rainwater for drinking is a different subject with different requirements, and that page covers the distinction.

Greywater

DANGER

Greywater must not go on anything eaten raw, and it must not be stored.

Greywater is water from baths, showers, basins and washing machines. It contains skin bacteria, food residues, detergents and salts, and the bacterial load rises quickly once it is standing.

Use it fresh, within a day. Do not store it: it turns rapidly and becomes genuinely unpleasant and hazardous.
Never on salad, herbs, strawberries or anything eaten uncooked, and never on the leaves of anything.
Apply to the soil, not the plant, and preferably below a mulch.
Fruit trees, ornamentals, hedges, lawns and crops that will be thoroughly cooked are the reasonable uses.
Never water from a toilet, or water that has washed nappies, or anything containing faecal matter. That is blackwater and it is a different category entirely.
Watch the detergents. Sodium-rich washing products damage soil structure over time, and bleach and softeners should not go on the garden at all. Simple soap is far better than most laundry products.
Rotate where you put it rather than repeatedly soaking one area.

The full treatment, including what to plumb and what not to, is on reuse greywater safely. Read that before setting anything up permanently.

Rationing in a real drought

When there genuinely is not enough, this is the order.

Sacrifice deliberately rather than spreading water thinly over everything. Half a bed watered properly beats a whole bed watered inadequately, which just wastes the water and loses the lot.

Harvest early. Anything nearly ready comes out rather than sitting in the ground consuming water and risking failure.

Weed hard. Weeds compete directly for soil moisture, and a weedy bed in a drought loses twice.

Do not feed. Fertiliser in dry conditions pushes soft growth the plant cannot support and can scorch roots.

Shade the vulnerable. Fleece, netting or a propped board over young plants in extreme heat reduces losses considerably.

Designing for less water

The measures that reduce the problem rather than managing it.

Organic matter, every year. It is the single biggest determinant of how much water a soil holds. A soil rich in organic matter behaves like a sponge; a depleted one sheds water and then dries out.
No-dig. Undisturbed soil retains structure and moisture far better. See starting a bed.
Windbreaks. Wind dries plants and soil surprisingly hard, and a hedge or a mesh screen reduces water demand noticeably.
Spacing. Slightly wider spacing in a dry site means less competition per plant.
Choose the crop to the site. Deep-rooted and drought-tolerant crops for the dry corner, thirsty ones near the tap.
Shade in summer. Some crops do better in partial shade in a hot dry summer than in full sun.
Time the sowing. Autumn-sown and early crops make use of winter and spring moisture and are finished before the dry period.
Grow more perennials. Fruit bushes, rhubarb and perennial herbs are established and deep-rooted and need almost nothing once settled.