How often should I water newly planted shrubs and perennials?

Why new plants need watering long after they look established, how much a single soak actually delivers, and the first-year regime that decides whether they survive.

Difficulty: beginner
Time: 20 min
Read: 5 min

Short answer

A new plant's roots are still inside the rootball it came in, so it can only drink from a volume the size of its old pot. Water it thoroughly at planting, then give it a proper soak once or twice a week through its first growing season — a full watering can per shrub, at the base — rather than a daily splash. Trees and shrubs need this through at least their first full year.

Almost every new planting that dies in its first summer dies of drought, and almost every one of those was watered. The problem is that a sprinkle over the surface wets the surrounding soil rather than the rootball, and the rootball is the only place the plant currently has roots.

What you'll need

Watering can or hose
Mulch material
A length of pipe or a cut bottle as a watering funnel (optional)

Step by step

Water thoroughly at planting.Fill the hole with water and let it drain before planting, then water again generously afterwards to settle the soil around the roots and remove air pockets. This first watering matters more than any later one.
Soak the rootball, not the surrounding soil.Water at the base, directly over where the pot went in. For the first season the plant can only drink from that volume, and water spread widely around it mostly goes to established neighbours.
Give enough per watering to matter.A full 10 litre can for a shrub, more for a tree, a couple of litres for a perennial. A slow trickle rather than a fast pour, so it soaks in rather than running off.
Water once or twice a week, not daily.A deep weekly soak drives roots out into the surrounding soil. Daily light watering keeps them in the rootball, which is precisely the problem you are trying to solve.
Keep going through the whole first growing season.March to October for a spring planting, and this includes wet weeks — light summer rain often does not penetrate a leafy canopy to the rootball beneath.
Give trees and large shrubs two full years.Their root systems take much longer to spread beyond the planting pit, and second-year losses on trees are common and avoidable.
Plant in autumn where you can.Autumn planting into warm moist soil gives the roots months to spread before the first summer, and it roughly halves the watering the plant needs the following year. It is the single biggest reduction in effort available.
Mulch after watering.Fifty to seventy-five millimetres of compost or bark over damp soil, kept clear of the stem. It substantially cuts evaporation. Applied to dry soil it does the opposite.
Check by digging, not by looking.Scrape back the mulch and push a finger into the rootball area. Damp at 50mm means leave it. Dry at 50mm means it needs a proper soak, not a splash.
Use a delivery aid on a big planting.A length of perforated pipe set vertically alongside the rootball at planting, or a cut-off bottle sunk neck-down beside it, delivers water straight to the roots rather than to the surface.
Watch for the signs of too much as well as too little.Yellowing lower leaves, a permanently wet planting hole and no new growth suggests a sump in heavy soil rather than drought. Both look like a struggling plant, so check the soil before adding more water.
Prioritise honestly in a dry spell.New plantings, containers and fruiting crops first. Established shrubs, borders and lawns can look after themselves in a normal British summer.

Tips

The commonest cause of first-year death is a wet garden and a dry rootball. Water where the pot went in.
Autumn planting is the closest thing to a free lunch in gardening. Fewer losses, less watering, better establishment.
A saucer-shaped depression left in the soil around a new shrub holds a can of water while it soaks in rather than letting it run away.

Common mistakes

Watering the whole bed lightly — The new plant's roots are only in its old rootball. Broad light watering mostly feeds the established plants around it.
Stopping when it looks established — A shrub can look perfectly healthy in June with roots that have barely left the pot shape. Keep going through the first full season, and two for trees.
Assuming rain has done the job — A summer shower often delivers only a few millimetres, and a leafy canopy sheds much of it away from the stem. Check with a finger.
Digging a compost-filled hole in heavy clay — It becomes a sump that fills with water and drowns the plant. Improve a wide area rather than one hole.

If it doesn't work

New shrub wilting although the bed looks damp

Cause: Rootball dry, surrounding soil wet — Fix: Soak directly over the rootball, slowly, with a full can.

Leaves browning at the edges from midsummer

Cause: Chronic under-watering through establishment — Fix: Deep soak weekly, mulch after watering, and continue into autumn.

Water runs off and does not soak in

Cause: Soil surface capped or hydrophobic — Fix: Scratch the surface, water slowly in stages, and mulch to prevent recurrence.

Yellow leaves and a permanently wet hole

Cause: Sump in heavy soil, not drought — Fix: Improve drainage across the bed, and stop watering until it dries.

Tree fine in year one, struggling in year two

Cause: Watering stopped too early — Fix: Water trees and large shrubs through two full growing seasons.

Questions people ask

How much water does a new shrub need?

Roughly 10 litres — a full watering can — once or twice a week through the first growing season, applied slowly at the base. A tree needs considerably more, and needs it for two years.

Do I need to water in winter?

Rarely, but evergreens planted in autumn can dry out in a cold windy spell when the ground is frozen and they cannot take up water. A soak before a hard freeze helps them.

Is it better to plant in spring or autumn?

Autumn, for almost everything hardy. The soil is warm, rain is likely, and the plant has months of root growth before it has to face a summer. Spring planting works but demands far more watering.