Plant seed in early fall outdoors in a protected bed where the seedlings are to grow or in pots which are wintered in a cold-frame. Cover the seed about one-half inch deep. They germinate a few weeks after the soil becomes warm in spring. The first summer, seedlings may grow six or eight inches and be strong enough to be set in the open nursery. They normally develop to flowering size in four to six years.
Nurserymen use cuttings and grafts to increase named varieties.
Cuttings of soft wood require much care. They develop slower than buds or grafts, but the plants are better. Cuttings are rooted in sand in a greenhouse or glass-covered frames where air can be kept moist. Cuttings must be taken while growth is most active, soon after flowering and before new terminal buds have formed. Make cuttings three or four inches long and remove all leaves except at the tip.