Calycanthus occidentalis or western spicebush blends into the background of the garden until the rosy buds form and swell in May and its unique solitary blooms begin unfurling in June. This year I’ve been avidly monitoring the buds each week, trying to predict when they will open. And just at the solstice, the first flowers appeared! The burgundy blossoms are reminiscent of magnolia blooms, and like magnolias have tepals (sepals and petals that both function as petals). The scent of the flowers is also distinctive, and reminds me of wine gone sour. The musky odor draws in small beetles to pollinate the flowers, and rewards them with a protein-rich meal of succulent tissue at the inner base of the tepals and stamens.
Calycanthus occidentalis is a locally common deciduous shrub native to the foothills of the North Coast Range and the Sierra Nevada in California, with a few populations in southern Oregon. In its native range it is an understory species, growing on moist canyon slopes, along creeks, and around lakes and ponds generally at mid to low elevations (below 4,000ft). The leaves are opposite, egg-shaped (ovate), bright green, and strongly aromatic when crushed.
In the Seattle area Calycanthus occidentalis prefers full sun or light shade and moist soil. In ideal conditions plants can reach 12 feet in height and width, and will continue blooming throughout the summer months. Deer avoid Calycanthus occidentalis, likely because the plant contains toxic alkaloids including calycanthine.
Calycanthine is a stimulant of the central nervous system, and if ingested can cause painful muscle contractions or tetanic seizures. The toxin is concentrated in the seeds of the plant, and although generally animals avoid the shrub, there are some historic reports of cattle and sheep poisonings after ingestion of the seeds.
To see Calycanthus occidentalis in the Washington Park Arboretum, head to the Cascadia Forest at the southern end of the park. Several specimens are blooming around the highest point in the garden.
Origin: California to southern Oregon
Height and Spread: Up to 12 feet tall and wide
Bloom time: June-August
Location: Cascadia high point in the Pacific Connections Garden