GARDEN TOPICS

Ashburton Guardian, Volume 70, Issue 211, 22 June 1950, Page 2

GARDEN TOPICS

TREE PRUNING

Written for the “Guardian” by A. F. MORGAN, N.D.11. (N.ZJ. F.R.I.H. (N.Z.)

The pruning of flowering shrubs has already been discussed, and to be correctly done requires a certain amount of knowledge of the flowering habits of the variety to be pruned if the best results are to be obtained. With tree pruning, however, there is not the same necessity, as a rule, to study flowering and non-flowering wood before branches' are removed, and in most cases it will be a question of removing branches from trees for tlie reason that they are overhanging the garden or house, or to improve the shape of the tree. Nevertheless, if comparatively large limbs have to be removed from a tree there are several points worth considering when carrying out the work. Between the bark and wood of trees there its an important layer of cells known as the cambium layer. These cells are able to produce new tissue to cover over any injury which may occur, but the callus can only grow across more or less flat or hollow surfaces, and caimot develop round sharp angles or cover over the end of a projecting stump. Pruning cuts, therefore, should always be made flush with the barrel of an existing limb or trunk, and stumps should never be left after pruning. If a stump is left, a ring of callus will develop round its base, but canont cover it until the growing trunk envelops the stump in the course of many years of growth, ft is likely, however, that the stump will have rotted long before then, leaving a wet hole in the side of the tree from which decay can spread down through the centre of the trunk. Cuts made level with the trunk, however, normally heal over completely, and this is the main aim when removing branches. To assist healing and to ensure that the exposed wood remains healthy until it has callused cv-3r, all cuts should be treatea with some antiseptic dressing as soon as they have been made. Many materials have been suggested and tried for this work, including white lead paint, coal tar, Stockholm tar and creosote. Experiments carried out in New Zealand have shown that bituminous paint is as cheap and efficient a wound covering as any. Many fungi readily attack the wood of trees if, they can gain admittance, causing the disease or even the death of shoots, branches, limbs or the whole tree. As there is always a serious risk of some disease gaining entry through pruning wounds, the necessity for close cuts which are able 'to callus over quickly, and an antiseptic dressing (to prevent the entry of disease spore.s until such time as the complete callus has formed) are important points with all tree pruning, and particularly when removing large limbs from fruiting trees. Branches should always be cut off in the following way to ensure that the wound is likely to heal as quickly as possible: Make a saw cut part way through underneath the branch, two feet or more out from the main trunk —this undercut ensures that a strip of bark is not torn off from the trunk when the branch breaks off. Next cut the branch from above, working slightly on the tree side of the undercut, and the branch should crack off when the cut is about half way through. Cut off the stump which is left, as close to the main trunk as possible. This usually means a long cut through the base, where the branch is buttressed into the tyunk, ( but the time taken is negligible compared with the shortening of the life of the tree that can result from incompetent pruning. Finally, trim the margins of the saw cut with a knife, and dress theV wound with bituminous paint.

Routine Work

The planting of shrubs, trees and herbaceous plants can be continued if the soil is not too wet. A hole should be dug for each plant large enough to enable all the roots to be spread out fully and not bunched up, and the plants should always be set in their new positions at about the same depth as they were growing before —as indicated by the soil marks on their stems. When planting in heavy soil it is best to dig the whole area over and not just excavate pockets into which' the new plants are put. Such pockets tend .to become waterlogged sumps into which surface water drains from the surrounding areas. If the soil is very poor, it pays to plant each shrub or tree in a barrow-load of good soil brought in from elsewhere. In any case, the establishment of each new plant will be greatly helped by the application of a handful of blood and bone to each hole, mixing part of it into the bottom of the hole and the rest with the soil as it is returned. Firm planting is most important and the soil must always be trodden firmly as it is replaced. If the soil is too wet to permit this to be done without churning it into mud, the plants should be heeled in and the work of planting postponed until conditions are more suitable.

Rose pruning can be carried out as opportunity occurs, and the beds then dug over and manured. Cow manure is the best possible manure for roses and could well be dug into the beds now when pruning is completed. Wood ash is also a valuable stimulant, for the roses and as there is usually plenty available at this time of year, could be scattered over the surface of the ground after digging. Wood ash should, however, never be used in the vicinity of rhododendrons, azaleas, ericas, or any plants which prefer an acid soil. Vegetables and Fruit ~

The pruning and spraying of fruit trees and bushes will be one of the main jobs at the moment. Primings should always be collected and burnt to destroy insect pests and diseases, and any large cuts made on fruit trees should be dressed with bituminous paint. This applies particularly when “heading back” large, or overgrown fruit trees. Lime sulphur and winter oil are the main sprays to use at the moment.