744 Platycladus orientalisCommon Names: oriental arborvitae, oriental thuja, biota Family: Cupressaceae (cypress Family)
Oriental arborvitae is a densely branched evergreen conifer that can get as much as 50 ft (15.2 m) tall with a spread of 20 ft (6.1 m), but in cultivation usually grows as a smaller, bushier shrub. It tends to have several to many stems, but can be trimmed to a single leader stem creating a treelike form. The overall shape is conical, with the crown becoming more irregular and spreading with age. The bark is rusty-brown and fibrous. The numerous slender ascending branches support shoots that spread out in flat, vertical planes. The leaves are like little scales overlapping and tightly packed on the shoots. The oblong cones are about 1 in (2.5 cm) long, held upright, and blue-green with a grayish waxy bloom. The cones are fleshy at first, becoming woody as they mature, and each of the 6-8 scales that cover the cone has a recurved, fleshy hook. Under the scales are wingless seeds.
Hortus Third lists 44 cultivars of this popular evergreen. 'Elegantissima' is perhaps the most common variety in cultivation; it is a cone-shaped shrub to 15 ft (4.6 m) tall with dense golden yellow foliage that changes to yellow-green in summer and bronze in winter. 'Aurea' gets 12-18 ft (3.7-5.5 m) tall and has yellowish foliage. 'Aurea Nana' is smaller, to 5 ft (1.5 m), with yellowish foliage. 'Filiformis Erecta' has drooping sprays of foliage and gets 5-6 ft (1.5-1.8 m) tall. 'Sunkist' is a tiny shrub to 24 in (61 cm) tall and wide
Oriental arborvitae, Platycladus orientalis, occurs naturally in western China and North Korea, with an isolated population in northeastern Iran. It usually grows on steep, rocky hillsides and cliffs. Oriental arborvitae is widely cultivated in gardens around the world.
CultureOriental arborvitae does well on poor, excessively drained soils, even those with high pH. Light: Full sun is best; oriental arborvitae also does okay in partial shade. Moisture: Oriental arborvitae is drought tolerant once established, but new plantings should be watered regularly for the first year. Hardiness: USDA Zones 6 - 11. Oriental arborvitae is a little less cold hardy than the American arborvitae, and the slender branches have a tendency to break under the weight of snow and ice. Most cultivars do best in the southern and southwestern U.S. Propagation: Propagate by seed which is produced abundantly and germinates readily.
Use Oriental arborvitae for formal hedges and as specimen shrubs. This is a neat shrub with tight, compact foliage held in dense, fanlike vertical sprays. Even mature specimens keep their dense foliage all the way to the ground, making oriental arborvitae a good choice for screens and windbreaks. They are used to anchor doors or foundation plantings (but plan for ultimate size!). The smaller cultivars are good in rock and succulent gardens. Oriental arborvitae is a good choice for chalky or alkaline soils that usually mean slow death for most cultivated plants. They do well on dry, rocky sites, and flourish even on crushed coral and sea shell "soils", although they are not very salt tolerant.
Oriental arborvitae is one of the best evergreen shrubs for low maintenance xeriscape gardens, especially in areas with low annual rainfall. They have been popular with homeowners in the southern and southwestern U.S., California, southern Europe and eastern Asia for many years. Old specimens sometimes can be found still persisting at abandoned home sites.
Oriental arborvitae is similar to American arborvitae (Thuja occidentalis), and formerly was classified in the same genus, but now is considered to be distinctive enough to warrant its own genus.
Contact with the foliage of arborvitaes may cause dermatitis in sensitive individuals.
Steve Christman 7/21/00, 10/28/04