The Osmanthus burkwoodii is an under-appreciated gem of our Seattle Japanese Garden — and a favourite of mine. Renowned plant explorer Dan Hinkley calls it “an aristocratic and highly refined member of the dicot family.” Consisting of about 30 species of evergreen shrubs and little trees, Osmanthus is notable for its attractive foliage and little , usually fragrant, flowers. The genus name derives from the Greek osme (fragrant) and anthos, (flower). Most species are native to woodlands within the temperate areas of Asia, but the genus also includes cultivars (cultivated varieties, sometimes called “garden varieties”), and species native to the occident .
There are several sorts of Osmanthus in our garden, but just one is spring-flowering — Osmanthus x burkwoodii. the foremost prominent kind here, it’s a cultivar, not a species plant.
Our garden also has several sorts of a fall-blooming species native to Japan (and Taiwan). Osmanthus heterophyllus (formerly O. ilicifolius, known in Japan as hiiragi) grows here in Areas I and O. it’s many common names, including Holly Leaf Osmanthus, Holly Tea Olive and False Holly. People often mistake it for a real holly (Ilex), but its spiny leaves are arranged “opposite on the stem” — unlike Ilex, which has alternating leaves. “Heterophyllus” means “having the foliage leaves of quite one form on an equivalent plant or stem.” Although the younger leaves are coarsely spiny, mature leaves are “entire” (simple in form, with smooth margins). Both kinds are thick, waxy in texture, and dark green.
O. heterophyllus blooms in late September and October, with intensely fragrant flowers that are mostly hidden by the foliage. They’re small, white, tubular, 4-lobed, and held in small clusters. Fruiting is rare . It grows at a moderate rate to about 8–10 feet tall , with an upright habit when young, spreading wider at maturity. In time, it can become treelike — to fifteen or more feet tall. Hardy to USDA Zone 6 (average winter temperature, -10 to 0 degrees F.), it’s widely planted in Japan — both pruned as a hedge and as a specimen shrub or tree during a mixed planting, allowed to retain a natural form. it had been first mentioned, within the 8th century, in Japan’s oldest surviving historical document , the Kojiki.
Holly Leaf Osmanthus burkwoodii grows in sun or part shade, and prefers moist, fertile, well-drained, acid soil. However, it tolerates drought, stressful urban conditions, and somewhat alkaline soils. Unless plants are stressed, it’s no serious pest or disease problems. It’s not problematic here within the geographic region, but can become invasive within the mid-Atlantic region of the U.S.
Minimal pruning is required. Remove misplaced, dead or diseased branches in late spring and apply a generous 5–7cm (2–3in) mulch of well-rotted garden compost or manure around the base of the plant.