This is a method of division effected by bending down and covering shoots at about the completion of spring growth. Usually summer layering is confined to the shoots of the same season's growth. The old plan was to slit the shoot at the point of burial in the soil, as shown in Fig. 17.
But a better method with young shoots liable to break is to twist the shoot at the point of burial. Severe twisting does not break the shoot and the cell injury starts the process of healing sooner than by slitting.
Fig. 17. - Layered branch split to favor root formation.
Fig. 18. - Summer layering of shrubs. (After Bailey.)
Summer layered shoots of a shrub are shown in Fig. 18. The figure does not show the pegging down. If notfastened down before covering with earth the spring of the branch and wind are apt to draw it gradually from its position before rooting. Very many trees and shrubs can be layered in this way, but some of them, such as cherry, plum, and birch, will require two or three years. The layer being attached to the mother plant is able to retain life and growth while the covered and injured part is getting ready to emit roots. In the South the rose and other shrubs are often layered in the air in pots, as shown at Fig. 19.
Fig. 19. - Layering in divided pots. (After Bailey.)
If young, excitable wood is used the twisted shoot will soon fill the pot with roots. The divided flower-pots shown are now manufactured.