Southern England is officially in drought. Groundwater levels across Hertfordshire have been declining since spring, Affinity Water remains in formal drought status, and the Environment Agency has classified the South East at “high” drought risk for summer 2026. If you have been wondering whether this dry spell is affecting the trees in your garden, the short answer is: almost certainly yes.
Drought stress is one of the most common causes of tree decline that we see as arborists, and it is also one of the most misunderstood. Homeowners tend to notice problems only once a tree looks visibly sick, by which point the damage has been building for weeks or months. The good news is that most established trees can survive a dry summer if you know what to look for and take a few straightforward steps.
How drought damages trees
Trees lose water through their leaves in a process called transpiration. In normal conditions, roots pull replacement water from the soil fast enough to keep pace. During prolonged dry spells, the soil dries out and that balance tips. The tree cannot absorb water quickly enough, so it starts rationing. Leaves curl, growth slows, and if the deficit continues, the tree begins shutting down branches to preserve the trunk and root system.
This is not just a cosmetic problem. A drought-stressed tree is a weakened tree. It becomes more susceptible to secondary attacks from fungi, bacteria, and pests that would not normally gain a foothold. It also becomes structurally less predictable. Bark can crack, deadwood increases, and root systems that have dried out lose their grip in the soil, raising the risk of windthrow later in the year when autumn storms arrive.
What to look for in your garden
The earliest sign of drought stress is wilting during the hottest part of the day, particularly in the afternoon, with partial recovery overnight. This is the tree conserving water and is not yet cause for alarm.
If conditions persist, you will start to see leaf scorch. Edges and tips of leaves turn brown and crispy, often starting with the oldest leaves or those most exposed to direct sun. On broadleaf trees like beech, oak, and lime, this can progress to entire branches carrying brown, papery foliage that stays attached rather than falling cleanly.
Premature leaf drop is the next stage. The tree sheds leaves it cannot sustain, starting from the crown and outer canopy. In a normal year, you would not expect significant leaf fall until October. If your tree is dropping green or yellow leaves in July or August, that is drought stress talking.
Conifers show different symptoms. Needles yellow from the inside out, and you may notice resin bleeding from the bark as the tree tries to seal stress fractures.
Which trees are most at risk in Hertfordshire
Not all species cope equally. Beech, which dominates the Chilterns landscape and is one of the most common garden trees across St Albans, Harpenden, and the villages along the A1(M) corridor, is particularly vulnerable. It is shallow-rooted and struggles on the thin chalk soils that underlie much of western Hertfordshire. The droughts of 2018 and 2022 killed or severely damaged beech trees across the Chilterns, and the conditions in 2026 are tracking similarly.
Birch and sycamore also suffer early. Both species have high transpiration rates and tend to show leaf scorch and premature drop before more drought-tolerant neighbours.
By contrast, native English oak and hornbeam are more resilient. Their deeper root systems and more conservative water use mean they tend to survive dry summers better, though even these species will show stress if the drought is severe enough.
Newly planted trees are in the highest risk category regardless of species. Any tree planted within the last two to three years has a limited root system and is almost entirely dependent on soil moisture in the top 30 centimetres. Without supplementary watering, young trees planted last autumn or this spring may not survive the summer.
What you can do
The single most effective thing a homeowner can do is water trees properly during dry spells. The key word is “properly.” A quick spray with the garden hose does very little. Surface watering encourages shallow root growth, which makes the problem worse in the long run.
Instead, water deeply and infrequently. For a mature tree, that means applying 50 to 100 litres of water slowly at the drip line (the outer edge of the canopy, not the base of the trunk) every two to three weeks during drought. A soaker hose or a bucket with a small hole in the bottom, left to drain slowly over an hour, gets water down to where the roots actually are.
For newly planted trees, water more frequently. 20 to 30 litres every three to four days during hot, dry weather. If you are facing hosepipe restrictions, grey water from baths and washing up is perfectly acceptable for trees, provided it has not been treated with bleach or strong detergents.
Mulching makes a significant difference. A ring of bark chip or composted woodchip, 8 to 10 centimetres deep and spread to at least a metre from the trunk, reduces soil evaporation dramatically and keeps root temperatures stable. Keep the mulch clear of the trunk itself to avoid creating damp conditions against the bark.
Avoid pruning during drought. Removing branches in summer forces the tree to divert energy into wound closure at exactly the time it can least afford to. If you have work planned, wait until late autumn or winter unless there is a safety issue with dead or hanging limbs.
When to call an arborist
Not every drought-stressed tree needs professional intervention, but there are situations where you should get a qualified arborist to take a look. If large branches are dying back, if bark is cracking or splitting, if the tree is leaning or the ground around the base has cracked, these are signs of structural compromise that need proper assessment.
If your tree is subject to a Tree Preservation Order or sits within a Conservation Area, you should be aware that any work, including removing dead branches, normally requires council consent. The exception is dead, dying, or dangerous trees, where emergency work is permitted, but even then you should notify the local planning authority as soon as possible and ideally before the work is carried out. Getting professional advice first protects you legally and ensures the right work is done.
It is also worth having mature or high-value trees inspected if they have been through multiple drought years. Cumulative stress weakens trees in ways that are not always visible from the ground. A qualified arborist can assess root stability, crown vitality, and structural integrity, and recommend whether any work is needed before winter.
The longer picture
Drought is not a one-off event any more. The pattern of hotter, drier summers is now established across southern England, and it is changing which tree species thrive in our gardens and landscapes. If you are planting new trees, it is worth thinking about species selection with future climate in mind. Hornbeam, field maple, and native oak are all strong choices for Hertfordshire gardens. They are tolerant of chalk soils, handle dry summers well, and provide excellent structure and wildlife value.
For existing trees, the best investment is consistent care. Trees that are well-maintained, properly mulched, and watered during critical dry spells are far more likely to recover from drought than those left entirely to fend for themselves.
If you are concerned about any trees on your property this summer, we are happy to take a look. A site visit gives you a clear picture of what condition your trees are in, what work (if any) is needed, and what you can do to protect them through the dry months ahead.
Call Evoke Tree Services on 01707 708202 or request a quote at www.evoketreeservices.co.uk
