Rhododendron

Rhododendron species

Trees and Shrubs, Plants of Home and Garden, Bonsai

Surface-sow 2" apart, in peaty acidic medium, 60F/15C, in good indirect light. Cover until germinated; may benefit from 3 weeks in fridge after sowing. Protect seedlings from the full sun first year; older plants usually also benefit from partial shade. Well-drained rich soil, good moisture required. Zone 4-8; since species have been widely hybridized, check carefully that a given specimen is suitable to your area

Indoor specimens may be moved into a sheltered spot in the garden when warmer in spring, and moved inside before last frost. Rhododendrons are widely used for bonsai; some, including Rhododendron indicum, Rhododendron kiusianum, or satsuki and kyushu azaleas, can even be grown as indoor bonsai, in a cool room, or grown outside summer, and brought in with harsher winters

Take 3" cuttings in late summer, remove the terminal bud and all but the top whorl of leaves. Along the lower 1" of the cutting make a shallow vertical incision through the thin bark. Dip cut surfaces in strong rooting hormone, and keep warm. Very slow and difficult to root. Multiplication by tourniquet air layering, in early spring, is also slow. Cultivars may also be propagated using side veneer grafting

Note that azaleas may be considered a sub-genus of Rhododendron, and that growing conditions for the two are very similar