There are some trees that multiply asexually, i.e. by vegetative means. In one such example, root suckers, new individuals grow from the roots of the parent tree, which may soon be surrounded by a whole group of young trees. This means of reproduction is found in the aspen, white poplar, black locust, wild cherry, etc. Their root system is usually spread out wide, and the root suckers may appear as far as twenty metres from the trunk. These suckers grow in great abundance, particularly when the parent tree is felled, or when one or more of its surface roots is severed or damaged. Stump suckers grow from latent or adventitious buds low down on trunks or on root bases, but do not form independent trees unless the original is felled. This ability is not the same in all trees. Conifers generally lack it altogether, and in early youth it is found only in the yew, eastern arbor-vitae and some cypresses. Almost all broad-leaved trees exhibit this ability in youth, but later, after the age of maturity, it disappears in some although it is retained undiminished in others. The group of trees with a constant ability to produce suckers in great abundance includes the willow, poplar, lime, hornbeam, alder. Black locust, elm and oak, those with a moderate output include the maple, ash and mountain ash. In advanced age the beech and birch sucker poorly. Suckering of this sort is not important in the wild, since under these conditions, a new individual can spring up only in place of an old tree, from its remains. Man makes far greater use of it in forestry, where over the generations trees are renewed from stumps, and also artificially propagated. In planting new forests, willows and poplars are grown directly from cuttings, as are most ornamental trees and shrubs.
Some trees can also multiply by their pendulous branches touching the soil and sending out roots. Their tips then grow upward, and new individuals are formed. This method is characteristic of the Norway spruce in high mountain areas, the lime growing in stone debris or parks, the arbor-vitae and many ornamental shrubs.