A tree can look healthy from the kitchen window while a serious problem develops in its crown, roots or trunk. Knowing the five signs of tree disease gives homeowners a better chance of acting before weak branches, falling timber or spreading infection affect the garden, fence, driveway or property.
Not every patch of brown foliage means a tree is diseased. Dry spells, late frosts, compacted soil and damage to roots can all cause stress. However, when changes persist, worsen quickly or appear alongside decay and dieback, the safest approach is a professional assessment. A close inspection can establish whether the tree can be managed through careful pruning or whether removal is the sensible option.
Five signs of tree disease to look out for
1. Dead, thinning or discoloured foliage
A healthy established tree should produce foliage that is broadly consistent across its crown for the season. One of the first visible warning signs is thinning growth, unusually small leaves, browning at the edges or sections of the canopy that fail to leaf up when the rest of the tree does.
Look for dead twigs at the branch ends, bare patches in one side of the crown and leaves that turn yellow, brown or black well before autumn. On evergreens, needles may fade, redden or drop in larger numbers than usual. A small amount of natural leaf fall is normal, but a sudden change across a large area is worth investigating.
The pattern matters. Damage limited to the windward side may point to exposure or storm damage, while decline beginning at the tips and moving inwards can suggest disease, drought stress or a root problem. Do not assume a fertiliser will solve it. Adding the wrong treatment can be a waste of money and may not address the cause.
2. Fungal growth on the trunk or around the base
Mushrooms and bracket fungi growing from a trunk, stump or root area are a clear reason to arrange an inspection. Some fungi grow on dead wood nearby and are not automatically a threat to a living tree. Others indicate internal decay that can reduce the tree’s structural strength long before the outside looks seriously damaged.
Bracket-shaped growths attached directly to the trunk deserve particular attention, especially where they appear near the base or beside a large old wound. The same applies to repeated clusters of mushrooms around the root zone, changes in bark texture and a hollow sound when the trunk is carefully tapped.
Fungal decay does not always mean a tree must be removed immediately. Its significance depends on the tree species, the type and position of decay, the amount of sound timber remaining and what the tree could strike if it failed. A tree in an open corner of a large garden presents a different level of risk from one leaning over a roof, public footpath, parked cars or a boundary fence.
3. Cracks, cavities and loose bark
Deep vertical cracks, open splits and cavities in a trunk or major limb should never be ignored. Trees can naturally compartmentalise some old injuries, but openings also allow water and decay organisms into the timber. Over time, sound wood may be lost inside a branch that still carries a full canopy.
Watch for bark that is peeling away in sizeable strips, dark wet-looking patches, sunken areas, or weeping sap from a wound. These symptoms can follow mechanical damage, poor previous pruning or infection. In practical terms, they can also make a limb less reliable in high winds.
Do not try to fill a cavity, cut back large limbs yourself or remove loose branches from a ladder. Cutting in the wrong place can make the wound larger and create an immediate safety hazard. A qualified tree contractor can inspect the extent of the damage from the ground and, where needed, carry out controlled pruning or removal with the right access and protection in place.
4. Dieback in the crown and falling branches
Crown dieback is when branches begin to die from their outer tips towards the main structure of the tree. It can leave a sparse, uneven outline and a growing amount of deadwood among otherwise live branches. You may notice small sticks on the lawn at first, followed by larger dead branches after windy weather.
Deadwood is not always caused by disease. Mature trees naturally shed some branches, and storm damage can break healthy limbs. The concern rises when dead branches are widespread, when new shoots are sparse, or when the decline happens over more than one season.
This is particularly relevant in gardens where trees overhang patios, driveways, sheds, play areas or neighbouring boundaries. A branch that looks secure from below may have weak attachment points or internal decay. Planned deadwood removal and crown work can often reduce the immediate risk while allowing a suitable tree to remain in place. Where the overall condition is poor, removal may be the more responsible long-term choice.
5. Changes around the roots, base or lean of the tree
The roots are hidden, so their problems are easily missed until the tree begins to show obvious stress above ground. Check the base of the trunk for cracks in the surrounding soil, raised roots, soft or decaying timber, new fungal growth and areas where the ground appears to be lifting.
A new lean is a serious warning sign, especially after prolonged rain or strong winds. Not every leaning tree is unsafe – some have grown at an angle for decades and remain stable. The key issue is change. If a tree has recently shifted, the soil has heaved on one side, or roots have been damaged during building work, drainage work or excavation, it should be assessed promptly.
Root damage can also show up as reduced leaf growth, early autumn colour and dieback in the crown. This is why cutting or digging near mature trees needs care. Roots often extend well beyond the visible canopy, and severing a major root may affect both the tree’s health and its stability.
When a tree becomes an urgent safety concern
Disease is not always an emergency, but certain symptoms should not wait for a routine visit. Contact a professional promptly if a large branch has split, a tree has moved after a storm, visible decay sits beneath a heavy limb, or dead branches are hanging above an entrance, road or neighbouring property.
Until the tree has been checked, keep people, pets and vehicles away from the area where possible. Avoid parking beneath the canopy or allowing children to play nearby. If a damaged tree is affecting access, fencing or a building, take clear photographs from a safe distance, but do not climb, pull or attempt to brace it yourself.
A safety-led inspection considers more than the visible symptom. It looks at the tree’s condition, its position, nearby structures, access for equipment and the safest way to complete any necessary work without causing further damage to lawns, paving or boundaries.
What a professional assessment can tell you
A proper tree assessment should provide plain answers rather than unnecessary alarm. In some cases, selective removal of deadwood, a crown reduction or the removal of a damaged limb is enough to make the tree safer and improve light in the garden. In others, extensive decay, repeated branch failure or root instability may mean the tree has reached the point where removal is justified.
The right recommendation depends on the individual site. A small ornamental tree beside a fence may be dealt with quickly, while a mature specimen close to a house needs a carefully planned approach. Access restrictions, overhead services, neighbouring gardens and the location of gates, sheds and fence lines all affect how the work should be organised.
At Abbey Tree and Fencing Services, advice is based on what will leave the property safer, tidier and easier to manage – not on selling work that is not needed. Where tree work affects an existing boundary, the job should also include protecting fencing and leaving the area clear once the work is complete.
A sensible next step for a changing tree
Take note of when you first saw the change and whether it followed storms, dry weather, groundworks or pruning. A few photographs taken from the same position over several weeks can help show whether the condition is stable or getting worse. But if the tree is close to your home, driveway or boundary, do not wait for a visible failure before asking for advice.
A timely inspection can turn an uncertain problem into a clear, practical plan – helping you protect your property while giving a suitable tree the best chance of remaining safely in the garden.