CHAPTER XXI

YOUNG TREES AND SUNSTROKE

It is most noticeable that the stems of young trees of from 8 to about 14 feet in height are apt in some seasons to get much damaged, so much so that the trees are rarely satisfactory for some years afterwards, even if they do not die outright. The mischief is usually not seen until it is too late to mend matters, and is found more as a rule on young trees with small heads standing out singly than where they are planted amongst undergrowth or in partial shade. If careful notice is taken it will be found that the stems are damaged on the south side, or it may be east or west of south, but never on the north side, and this is directly caused by the rays of the sun being too hot for the young stems to bear. The trees most liable to sunstroke--which it practically amounts to--are the Lime, Willow, Horse Chestnut, Sweet Chestnut, Birch, Mountain Ash, Ash, and Plane, and generally in the order they are given, the softer wooded trees suffering more severely than those of harder growth. The Oak, Elm, and Beech are seldom much damaged by the sun, though in cases of failure it will be well to notice the stems and see how far the direct rays of the sun are responsible for the death of the tree.

The first marks of sunstroke are seen in the shape of longitudinal cracks in the bark, which is also slightly browned and flattened, as if there were a hollow beneath. The part affected is from about 1 to 3 feet in length, and from 1 to 3 inches in width. If the bark is cut away the wood beneath will be found perfectly firm, but hard and dry, more like a piece of seasoned wood than part of a growing tree. When such is the case the only thing that can be done is to cut away the bark back to the living tissue, thoroughly coat the wound with gas tar, and shade the stem afterwards with a few branches or something that does not need to be fastened on the stem. Hay or straw bands cannot be altogether recommended, as anything which excludes the light tends to the softening of the young bark. This should be avoided, as the firmer the bark the better will be the ultimate success of the tree. Iron tree-guards, though not beautiful, have the advantage of protecting the stems of young trees from the sun as well as from the attacks of animals. In addition to the slight shade they give, the iron, being a good conductor of heat, takes up a large amount of the heat rays which would otherwise be directed full upon the stem.

A hot and dry season is no more likely to cause sunstroke than a wet one, and probably not so much, as we have noticed it in sunless years quite as much as in bright summers. The time when it is most likely to happen is when a few days of hot sunshine follow a spell of wet weather, as the wood is then soft and full of moisture, and is more liable to be scorched than during a period of prolonged sunshine.

When trees are planted out singly it is well to choose those with spreading heads and low stems, as then the tree will shade itself to a great extent, the short amount of bare stem being less exposed to the sun's rays than a taller one. After all, this is only Nature's method of protection, as, in a wild state, no young tree is bare-stemmed, except in a wood, where it is shaded by those near it. On the edge of a wood, or in the open, young trees are furnished to the ground with foliage, which is not shed until the stem has become hardened enough to withstand climatic vicissitudes. If trees with tall stems are the only ones available, then the stems should be shaded by some means for a year or two, especially when they have become established and are making strong, sappy growths, as the stem is practically in the same condition and apt to be scorched by a sudden burst of hot sunshine.

GOAT AND WOOD-LEOPARD MOTHS

Sunstroke must not be confounded with the ravages of the caterpillars of the Goat Moth and Wood-Leopard Moth, the external signs of which are much the same, but on the bark being removed one or two channels almost the size of a man's little finger are to be seen, together with accumulations of wet sawdust-like material deposited by the caterpillar. These are exterminated by thrusting a stout wire into the channels until the grub is killed, and afterwards cutting away the dead bark and tarring the wound thoroughly. The tree should also be securely staked, otherwise it will probably snap off in the first high wind.