Tree health and safety

Councillor Patricia Wiltshire

Recent storms have made many of us acutely aware of the trees in Ashtead as well as their vulnerability to high winds. Several seemingly healthy trees crashed down across roads in Ashtead during recent storms, spectacular ones being two horse-chestnuts at the edge of the Woodfield on the road leading to Ashtead Station.

Councillor Patricia Wiltshire said “Councillor Hawksworth and I are concerned at the state of a considerable number of Ashtead trees, particularly those close to roads and paths. Many are heavily infested with mistletoe, and even more with dense growths of ivy.”

Mistletoe is spreading because of increasingly mild winters. This pest is distributed by birds, and is a parasite which sucks out water and essential nutrients from the tree. Whereas one or two mistletoe plants probably do little harm to an otherwise healthy, mature tree, some can have almost as much mistletoe as its own leafy canopy. Where this happens, the host tree is invariably weakened and will continue to sicken.

Where ivy has taken hold, and not only encircles the tree but reaches the canopy, the tree is at a severe disadvantage. There are conflicting opinions - some praise ivy as a source of nectar for bees, and berries for birds, in the late autumn and winter months. This is true, and there is little harm in ivy being allowed to grow on part of a tree, but its spread around the whole circumference of a tree should be controlled. It has been shown on rare occasions, badly to affect the production of healthy new tissues in the trunk. Ivy may not only compete with the tree for water and nutrients in the soil but, once it reaches the canopy, can over-grow the tree’s leaves and deprive them of light. A heavy burden of mistletoe and ivy can act as a sail and so contributes to lateral stress in high winds, increasing its likelihood of falling.

Ivy can reach such high densities that it creates a moist micro-environment on the surface of the bark, and harbour pests, particularly fungal spores. The stresses that mistletoe and ivy may cause can make a tree more vulnerable to fungal attack, and we have had some spectacular fungal infections of trees locally. An example is the large ash tree next to the playground in the recreation ground. Councillor Wiltshire requested the council to inspect and cut the huge branches and more cutting will happen to make it safe.

Some fungi remove the heartwood so that the tree becomes hollow and remains supported only by the thin band of living tissue under the bark. These trees can live for many years but may be particularly susceptible to high winds. Other fungi, such as the one causing ‘Ash Die-Back’, attack the living tissue so that the leaves wilt and the tree dies; here, the best course of action is to remove the stricken plant. Of course, a tree can suffer infection from both kinds of fungus, in which case it will be doomed and die relatively quickly.

Councillor Wiltshire said that she is pressing for more council inspections and the employment of more staff for this important role. She said “We must insist on regular assessment of tree health, and would ask you to be vigilant. Please report anything you find worrying to the council as quickly as possible. Your concerns can be logged via Mole Valley District Council website.” If the tree is your responsibility, consult a reputable tree surgeon.