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Tree Reproduction


How do trees reproduce their kind? Trees seem to share with all other living things an apprehension that their race may perish from the earth. It is to prevent this calamity that they feed and breathe and grow. As soon as they are old enough they produce flowers, mature seeds, and fling them forth. Their seed-sowing is a prodigal business. Every year a thousand of their offspring die for every one that lives. But that one is quite enough. One tree is sufficient to save the race.

The forms of these seeds are a constant marvel to the intelligent observer. The wonder grows when we study the uses they serve in distributing the species. Berries and other fleshy fruits tempt birds in whose crops the seeds lodge and they are afterwards dropped in regions far remote from the parent trees. The wind transports the winged seeds. Water carries the light ones. Squirrels and other animals store nuts and acorns in pockets here. There along their runways in the fall. Many of these seeds are left to germinate wherever they chance to be dropped.

The fur of animals may carry little burs like those of the beech nut. The spiny bur of the chestnut keeps animals from getting the seed. The husk and thick, rough shell protect walnuts and butternuts from being eaten. But the tree that depends entirely upon seeds as a means of reproducĀ­tion is seriously handicapped in the race. It has long been known that willows and some other trees could be reproduced by putting into soil a fresh piece of a branch or twig. The power to throw out leafy shoots and roots seems to be especially active in the cambium of these trees. The discovery of this fact came by observing that twigs broken off and drifted down stream took root where they lodged. Willow stakes set into the ground grow, and hedges are soon produced. Green willow fenceĀ­posts soon grow into roadside trees.

Another way of expressing the same exuberance of vitality is seen when willows are pollarded. A branch is cut off, and the cambium forms a number of buds below the wound from which strong watersprouts or suckers grow out. Bruising the stern has the same effect. The loss of a twig often sets the branch to pushing out dormant buds. Thus the crack willow and certain poplars cast off their catkins and push out just below them leafy side shoots to take their places. It is a common practice to cut back to stubs the long weak limbs of soft maples. A thicket of lusty shoots springs up, which in a few years, with judicious thinning, forms a strong, close, symmetrical head.

A twig drooping along the ground may strike root at a joint and form an independent plant when its connection with the main plant is severed. Raspberry canes bend over and root at the tips. So do viburnums. Roots of many trees may be cut into pieces and each produce a plant. Normally, roots have no buds, but the cutting of them may produce buds from which spring leafy shoots above ground. Many plants grow from root cuttings. The horse radish plant is so propagated. The hickory is multiplied in this way. The roots of many trees produce buds, and send up shoots, apparently without provocation. The failing of the tree's vitality seems to intensify this habit. It is a sort of life-insurance scheme. With many species of trees a fringe of suckers comes up at the junction between root and stem after the tree is cut down. A common sight is the rotting stump of a giant chestnut, around and out of which a half dozen sprouts have grown into good sized trees.

In short, many plants increase their kind by devices not at all connected with flower or fruit. Mall takes advantage of these suggestions of nature. Theoretically, every plant or tree may be propagated by the nurseryman from a mere slip or cutting. It is necessary only to provide the conditions favorable for growth.