Rhododendron macrophyllum, the Pacific rhododendron, California rosebay, California rhododendron, coast rhododendron or big leaf rhododendron, is a large-leaved species of Rhododendron native to the Pacific Coast of North America. It is the state flower of Washington.
Broadleaf evergreen shrub, erect, compact in the open but long stranggling branches when crowded, to 6-12 ft (1.8-3.7 m) tall, may even become a small tree 25 ft (7.6 m) high. Leaves simple, alternate, elliptic to oblong, 7.5-15 cm long, 3-8 cm wide, tapering at both ends, dark green above, paler below but often rusty-colored, petiole 1.3-2.5 cm long. Flowers 5-lobed, spreading bell-shaped, about 3.5 cm wide (or more), color varies from pale pink to a rosy purple, rarely white, green/brown spots on the upper lobe, edges crumpled, calyx small, 10 stamens, ovary covered with reddish down; flower clusters are terminal and may contain 20 or more blooms.It is an evergreen shrub growing up to 2–9 m (7–30 ft) tall. The leaves, retained for 2–3 years, are 7–23 cm (3–9 in) long and 3–7 cm (1–3 in) broad. The flowers are 2.8–4 cm (1.1–1.6 in) long, with five lobes on the corolla; color is usually pink, although variants exist.