1306 Buxus sinica var. insularisCommon Names: Korean boxwood,Wintergreen boxwood Family: Buxaceae (boxwood Family)
Here we discuss Buxus sinica var. insularis, the Korean boxwood. Other varieties of the species are not regularly found in cultivation.
Korean boxwood is very similar to Littleleaf boxwood (B. microphylla). Both are profusely branched evergreen shrubs with thin, elliptic-oblong, opposite leaves just ¾ in (19 mm) long. Korean boxwood produces flowers that are greenish yellow, whereas littleleaf boxwood’s flowers are more creamy white. Korean boxwood is a smaller shrub than littleleaf, getting just 2-4 ft (60-120 cm) in height. Korean boxwood is also much more cold hardy than other species. Also compare Korean boxwood to the European species, common boxwood (B. sempervirens), which is a larger, more open shrub with larger leaves and can eventually grow as tall as 10 ft (3 m).
The boxwoods have both male and female flowers on the same plants. Their star shaped flowers lack true petals - the star shape owes to the sepals. Flowers are borne in little clusters with a central female flower surrounded by several male flowers, recognized by their conspicuous yellow anthers. The tiny flowers are not especially showy, but are quite fragrant.
The most popular cultivar, and the only one with which we are familiar, is wintergreen boxwood, Buxus sinica var. insularis ‘Wintergreen’, which gets just 2-4 ft (60-120 cm) tall with a spread of 3-5 ft (90-150 cm), and is very cold hardy with foliage that stays dark green all winter. The Royal Horticultural Society calls it B. microphylla var. koreana ‘Winter Green’, and the American Horticultural Society treats it as a selection of B. sempervirens (common boxwood). Confused yet?
Buxus sinica occurs in temperate Asia, including Japan, eastern China, South Korea, and Taiwan. The variety, insularis, is restricted to Honshu Island in Japan and South Korea. The cultivar, ‘Wintergreen’ is of garden origin. Other species of Buxus occur in Europe, Africa, and Central America.
Boxwoods should be thinned annually to remove dead and damaged branches. Boxwoods do best when they have an organic mulch 2-4 in (5-10 cm) deep over their roots. Avoid cultivating around the bases because boxwoods have shallow roots. Light: Boxwoods do well in dappled shade, and best when they get full sun for just a portion of the day. Too much sun scorches the foliage. More shade is desirable in hotter climates. Moisture: The boxwoods like a soil that is close to neutral, pH 6.5 -7.4. They do best in a moist, but well drained soil of moderate fertility. A good layer of mulch is highly beneficial. Boxwoods do not take kindly to drought and should get about an inch (2.5 cm) of water per week. Yellowing leaves may be a sign the plant is not getting enough water. Hardiness: USDA Zones 5 - 9 . ‘Wintergreen’ is said to be hardy to zone 4, if given some winter protection. It retains its dark green color better than other boxwoods which tend to turn purplish when they get too cold. Propagation: Boxwoods are easy to root from tip cuttings with a “heel” taken in spring or summer.
Like the other boxwoods, Korean boxwood is extremely tolerant of pruning and shearing. It is used for low hedges and foundation plantings, and is especially appropriate in formal gardens. To create the perfect hedge, space wintergreen boxwoods 2-4 ft (60-120 cm) apart. Prune boxwood hedges right after the rush of new growth in spring, and again later in the summer.
Boxwoods are an important component in English formal gardens where they are used as dividers between beds and as borders along paths. They can be pruned as specimen elements to mark important places in the garden such as entry and turn junctions. The boxwoods are perfect subjects for topiary and bonsai, and wintergreen boxwood, with its short stature and tiny leaves, is probably the best of the lot.
Fun fact: Deer and rabbits avoid dining on boxwood.
There are at least 70 species of boxwoods. All are profusely branched shrubs or small trees. The taxonomy of the boxwoods is confused, to say the least. Buxus sinica var. insularis is treated by the Royal Horticultural Society as B. microphylla var. koreana, and has been treated by other authorities as B. microphylla var. sinica. See Floridata’s profile on littleleaf boxwood (B. microphylla) for more confusion about the taxonomy of these little Asia shrubs.
Steve Christman 3/24/18