The portion of the stem that is covered with soil will develop roots. Making a small wound on the portion of the stem that is to be buried will help to stimulate root development. To make this wound, using a knife, simply make an angled cut into the stem. As you bend the stem to force it into the hole, be careful not to break the stem at the cut. It is also beneficial to treat the wounded area with a powder root inducing compound, available at most garden centers.
Some branches are more rigid than others.
It may be necessary to anchor the branch down using a piece of heavy wire bent in a U, or a fork shaped branch. Or you can hold the branch down by placing some form of weight on the soil covering the branch. Layering is a propagation technique that can be done in the fall or spring. May. Layering yields great success on many deciduous shrubs because you are not actually removing the branch from the plant at the time of the layering process. The new plant that you are attempting to propagate is still attached to, and being nurtured by the parent plant throughout the entire process.