A hardwood cutting is made during the dormant season from the fully mature stem of a deciduous tree or shrub. Because the cutting has no leaves, the degree of environmental control required for successful propagation is minimal.
As with virtually all methods of vegetative propagation, it is the preparation of the parent plant, by pruning rigorously a year before the cutting is to be taken, that is possibly the single most important factor in the ultimate success of rooting a hardwood cutting. Hard, rigorous pruning will encourage stems with a high capability of producing roots.
A stem grows at different speeds throughout the season. It develops fastest in spring, its rate slowly declining until autumn, when growth c eases altogether. Even by the end of the growing season, the base of a stem that was produced in spring still has the greatest ability to develop roots, and it should be used for most hardwood cuttings.
Plants, such as willows, poplars and currants, that root easily show very little decline in their ability to produce roots anywhere along the stem and so virtually any part of the stem can be made into cuttings.
With plants, such as coloured-leaf plums, that are difficult to root include the swollen base in the cutting, which should be cut flush with the stem (see page 9).
Hardwood cuttings can be taken any time during the dormant season, but they will be most successful at "leaf-fall" and just before the leaf-buds break; their lowest capacity to root is in the early new year.
Cuttings made just before the dormant buds break will need a protected environ-
1 Prune the parent plant rigorously during the dormant season.
2 Run a hand down a leafy stem on the parent plant in early autumn.
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ment, such as a cold frame, or very careful timing to avoid leaves being produced before roots, so causing the cutting to lose water too quickly and die. Thus it is more satisfactory to take cuttings at "leaf-fall", when they can be planted in the open ground.
Conventional "leaf-fall" occurs when the stem, having produced a corky abscission layer to isolate each leaf, has its leaves removed by rain, frost or wind. However, as far as the plant is concerned, a leaf is isolated as soon as the corky abscission layer is complete, and this in effect is "leaf-fall".
Run a hand down the stem of a plant. If the leaves fall off, the corky abscission layer is complete, and the time, therefore, is right to take hardwood cuttings.
Size of a hardwood cutting
Although traditionally hardwood cuttings are made between 10-14 in long, a shorter length is much more successful.
Hardwood cuttings, although leafless, will still lose some water by evaporation from their surface. The commonest reason why these cuttings may fail to develop roots is because they are allowed to dry out. To avoid water loss, expose as little of the cutting as possible above the ground. However, if the cutting is planted too deep, the buds will no) grow properly. Thus it is vital to expose sufficient of the cutting above ground for about three buds to develop. In practice the third bud can be planted just below.ground level as at that depth its growth will not be inhibited. Therefore, for most plants, only 1 in or so of the cutting need be above ground. . A cutting initially develops roots both along the stem and from the cut area at its base. Gradually, the roots along the stem disappear and the root system of the new plant develops from the basal roots alone. Therefore these basal roots should be encouraged by applying a rooting hormone to the cutting and by
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