Why Newly Planted Trees Feel Drought First

A sapling lifted from a nursery bed or a pot arrives with a rootball far smaller than the canopy it once supported. For the first two or three summers, those roots are still finding their way out into the surrounding soil, and until they do, the tree depends almost entirely on the moisture held in that small volume of earth. A mature oak can pull water from metres down; a whip planted last November cannot. That is why a dry fortnight in June can do more damage to a young hedge or standard than a hard frost in January.

Dry spells in the UK are rarely dramatic. We are not talking about Mediterranean heat, but two or three weeks of warm days, a stiff breeze and no meaningful rain will dry the top 20cm of soil quite thoroughly. That is exactly the layer where young roots are working. The damage is often invisible at first — leaves may simply look a little dull — and by the time foliage is crisp and brown, the tree has already been struggling for a while.

Watering That Actually Reaches the Roots

The single most common mistake is little and often. A quick splash from a watering can every evening wets the surface, encourages shallow rooting and evaporates before it has done any good. Young trees want a thorough soak less frequently, so the water moves down past the surface and the roots follow it.

• Give roughly 10–20 litres per tree, twice a week in dry weather — more for larger saplings or very light, sandy soils.
• Water slowly. Trickle it in over several minutes rather than emptying the can in one go. A punctured plastic bottle or a slowly dripping hose laid at the base works well.
• Aim at the rootball, not the trunk. Water in a ring around the base, extending to just beyond the original planting hole.
• Water in the evening or early morning so less is lost to evaporation, and never in the heat of midday.
• Check before you water. Push a finger or a slim cane 10cm into the soil. If it comes up damp, leave it. Overwatering is possible, and soggy roots rot.

If you are planting this autumn, a shallow depression or a raised ring of soil around each tree — a watering basin — will hold water over the root zone instead of letting it run off across the surface.

Mulching: The Quiet Workhorse

A good mulch is the closest thing to insurance a young tree can have. It slows evaporation from the soil surface, keeps the ground cooler, suppresses weeds that would otherwise compete for every drop, and gradually improves soil structure as it breaks down.

Spread well-rotted bark, composted green waste or leafmould in a layer about 5–8cm deep, extending out to at least the spread of the branches, and a little beyond. The crucial detail is the gap: keep mulch clear of the trunk by a good 10cm, leaving a shallow doughnut rather than a mound. Mulch piled against bark holds damp against the stem and invites rot, disease and mice.

Apply it in spring while the soil is still moist, or straight after planting. If the ground is already dry, water thoroughly first, then mulch — otherwise you are simply sealing in the drought. Grass and weeds should be cleared from the ring before mulching, as mulch alone will not kill established perennial weeds.

Shade, Shelter and the Wind Problem

Wind dries a tree faster than sunshine does. A sapling exposed to a steady breeze loses water through its leaves quicker than the roots can replace it, and the damage can appear within days. A temporary screen of horticultural fleece or a hessian wrap on the windward side can make a real difference in an exposed garden or a new hedgerow on open ground.

A little shade over the root zone also helps. A thin layer of loose organic matter, or the natural shade cast by neighbouring plants, keeps soil temperatures down. Avoid piling anything directly against the trunk, and remember to remove tree guards and ties as the tree grows — a guard left on too long can rub bark and trap heat.

Reading the Signs, and the Long View

Learn what your tree is telling you. Leaves that curl inwards, droop at the tips or turn a dull grey-green early in a dry spell are asking for water. Yellowing lower leaves, brown edges and leaf drop in July are signs the tree is already shedding foliage to survive. By contrast, wilted leaves that recover overnight usually mean the roots have dried — but watering can still save it.

Do not be tempted to feed a drought-stressed sapling. Fertiliser draws water out of roots and can burn them. Wait until growth resumes and the soil is properly moist.

Within three or four seasons, a well-tended young tree will have rooted widely enough to look after itself through most British summers. Until then, a weekly walk with a can and a hand in the soil is the most valuable gardening you can do — and the reward, a lifetime of shade, blossom and birdsong, is one of the best investments a garden can make.