Aerial propagation

Press, 12 October 1979, Page 14

Aerial propagation

GARDENING

By

M.Lusty

There are many forms of plant propagation techniques and some of them require a rather more specialised approach than others.

Aerial, Chinese or marcottage layering is one form of propagation which is a little more involved than usual. The technique, which was originally used by the Chinese, is a method of propagating plants whose branches are too stiff to apply the more conventional form of soil layering or where suckers are not produced. It is also an excellent and desirable way to increase stock of valuable plants. Some of the plants which can be propagated by means of aerial layering include Acer, Cornus, Croton, Cytisus, Ficus, Hamamelis,, Hibiscus, Magnolia, Mahonia, Nerium, Rhododendron, Syringa, Viburnum and Wistaria. The period between October and November presents the best conditions for this operation. Requirements are a verj' sharp knife, clear polythene sheeting, tape or rubber bands, rooting hormone and sphagnum moss. Shoots which were formed in the previous season, and 15cm to 30cm in length, are required. After the lower leaves of the selected shoot have been stripped one of two methods can be employed for propagation. Method 1. A ring of bark 7cm to 15cm wide is cut off the stem. Method 2. A slanting

cut is made on one or either side of the shoot, from just below a node and directed upwards for about 25mm. It is kept open by inserting a small wedge of wood or by plugging with the rooting medium which is going to be used. The ringed or cut shoot area is then dusted with an appropriate growthpromoting hormone, such as idolyl butric acid mixed

with talc. Proprietary brands of rooting hormones are available from most nurseries. The next step is to pack the sphagnum moss around the cut or exposed region to give a complete cover. The moss should be thoroughly wetted and any excess squeezed out before it is placed in position. The hormone could actually be incorporated in the moss instead of being

applied direct to the shoot. It is necessary to put a. tight wrap over the mosscovered portion of the*/ stem. This is where the clear polythene comes into use. A thin grade of polythene is desirable, either a square sheet of 250 mm dimensions, or a 75 to 100 mm strip can be used. Whichever is applied ,it should be securely wrapped around the mosscovered poition of the stem and held in place with tape or rubber bands to prevent drying out. Care should be taken when putting the ties in position that they are not so tight that they are liable to cause constriction or cut into the shoot. The branch with the aerial layer on it may re-. - quire support to prevent damage in strong wind or to brace it against the additional load on it. A stick, such as a light piece of bamboo cane, can be bound to it. A good root system should be evident following inspection the follow-' ing autumn. The aerial! layer can then be cut from i. the branch, the tape and • polythene removed with i care, and the new plant * potted up or planted out. I