Madam, - I refer to the short piece on the subject of ivy in the Horizons column (Weekend Review, November 9th).
As a professional botanist and plant ecologist I am concerned at the bad press that ivy consistently receives being variously emotively and perjoratively being described as a "threat", "a parasite" "infesting and distorting tree growth", etc. This is essentially the lay person's view but the biologist, ecologist, or naturalist views the species in a very different light.
The first myth that must be dispelled is that ivy is a parasite. This is not so. It is an evergreen climber, clinger and hanger-on, and it takes no nourishment at all from the plant, shrub or tree that physically supports it.
In the majority of situations ivy is in ecological equilibrium with its supporting tree and the associated habitat. The only situation where the species may begin to cause trouble is when it reaches the top of a tree and begins to branch out.
Then the sheer weight of foliage may cause the tree to topple. Even then, the tree surgeon/silvicultural jury is out on that issue.
In a garden or parkland situation there are aesthetic arguments for the control or removal of ivy on specimen trees. In the wider countryside it should be the case of leaving the tree, the ivy and the other components of the habitat very much alone to interact naturally with each other.
Ivy here may overwhelm trees and cause them to topple but the ecological benefits of this are considerable. This initiates yet another phase in the cycle of birth, death, decay and re-birth which is an essential part of any healthy and evolving ecosysytem.
The removal of ivy in this setting is not only unecessary but destructive because of the pivotal role it plays in providing food and shelter for a host of plants and animals.
This is especially so during the leaner months of winter and early spring as its late flowering and fruiting are the mainstay of the diet of many insects, birds and mammals. Without ivy this ecosystem is depleted and loses its diversity.
And aesthetically the evergreen dressing which ivy gives to the bare wooded, winter landscape is all the more cheering for the foil it presents to the sombre surrounds of the countryside.
Richard Mabey in Flora Brittanica has documented many of the widespread uses to which ivy was traditionally put by communities for herbal and veterinary purposes, and there is a wealth of lore surrounding its use in rituals and festivals some of which have survived until today e.g. its inclusion in Christmas greenery.
So, may I ask that a less jaundiced view be taken of ivy? We are ourselves are depleted if we ignore its pivotal ecological role and its historical importance in human folklore and ethno-botany.
Dr TOM CURTIS,
Davitt Road,
Bray,
Co. Wicklow.