Rhododendron macrophyllum aka California Rose Bay

Rhododendron macrophyllum is also called western rhododendron. This shrub stays green all year. It belongs to the heath family, Ericaceae. Its native range runs from British Columbia to northern California. In Oregon, it grows along the coast's foothills and the Cascades. It grows from sea level into the mountains. It is also the state flower of Washington.

Garden plants reach about 6–13 feet (1.8–4 metres) tall. They can spread to 13 feet (4 metres) wide. Some form small trees that reach 25 feet (7.6 metres). The shrub grows upright and has a branched crown. In open sites, it keeps a compact shape. In crowded sites, it grows long branches. Its thin, gray-brown bark can be smooth or scaly. Young shoots are stout, green, and free of hairs. With age, they turn reddish brown or gray. Large, pointed buds have many scales that overlap.

The thick, leathery leaves stay on the plant year-round. They are oval to oblong, with smooth edges. Some leaf edges roll. The tops are dark green. The undersides look paler or rusty. Leaves grow in turns along stems but crowd at branch tips. Flowers open from late spring into early summer. Each bell-shaped bloom has five lobes and ten stamens. Blooms range from pale pink to rose-purple. Rare blooms are white. Green-brown or yellow-brown spots mark the upper lobes. Groups at shoot tips can hold twenty or more flowers. Small brown seed pods follow, each with five parts.

Give this shrub moist, acidic soil that drains well. Add plenty of humus, and keep the roots from drying out. The RHS favors part shade or dappled shade. Oregon State also lists sun as a good choice. Shelter it from strong winds, and avoid frost pockets. Add leaf mould as mulch each year. The RHS rates its hardiness H6. Plants reach full size in about five to ten years. They need little pruning. Grow new plants from seed or semi-ripe cuttings in late summer. You can also use layering in autumn.

Its year-round leaves and spring blooms suit borders and informal gardens. The RHS also lists courtyard gardens and beds beside walls. Watch for vine weevils and whiteflies. Leafhoppers and lacebugs may attack, too. Other pests include scale insects, caterpillars, and aphids. Diseases include powdery mildew, honey fungus, and silver leaf. Phytophthora can cause problems, too. This is not a food plant. Eating it can harm people. It can also harm dogs, cats, rabbits, and tortoises. The RHS advises gloves and other protective gear when handling it.