The quest for plants which hold up throughout all four seasons can be long and frustrating. Many plants are not looking their best during the dog days of summer, while others shed leaves or retreat below ground during the winter. sweet box or Sarcococca is one plant which can take it all. The genus is comprised of about 18 species from the Himalayas and southeast Asia and are related to boxwoods.
Undoubtedly the most popular and most cold hardy is the dwarf Himalayan sweet box, S. hookeriana var. humilis often listed simply as S. humilis. This tough, evergreen, woody ground cover (to 16" tall) can quickly spread by underground stems to form dense weed-blocking mats. Like all of the sweet boxes, the flowers are only marginally attractive as they are mostly hidden by the glossy, 3" leaves. There is no hiding the heady fragrance in late winter or early spring when the flowers open, though. The sweet smell wafts through the garden leading the unknowing on a scavenger hunt for the perpetrator. Small blue-black fruits follow the flowers over the summer. The Himalayan sweet box, S. hookeriana var. hookeriana, is a much larger shrub growing to the relatively giant size of 4'–5'. It does sucker like its diminutive relative, but at a much more restrained rate. In other respects, it is very similar to the dwarf form as is the variety digyna which has narrowly pointed leaves.
The ruscus-leaved sweet box, S. ruscifolia, does not spread like its Himalayan cousins, but is evergreen and flowers in the early spring. The 3' wide and tall shrub is composed of arching branches which bear small (2") pointed, dark, glossy green leaves. The fragrant flowers are followed by dark maroon red fruits. This shrub, along with S. saligna or willow-leaved sweet box, is somewhat tender and is probably best in warmer coastal areas or in protected spots near a wall. The willow-leaved sweet box, as its name implies, has long 5" narrow leaves on its arching stems. The shrub grows to about 3' tall and can sucker to nearly twice as wide. The winter flowers are a bit greenish and belie their name by failing to be fragrant, but do win marks for their largish (0.5") purple-black fruits. The only other sweet box regularly found in the nursery trade in the United States is the very hardy S. confusa. This sweet box lives up to expectations with exceptionally fragrant, late winter flowers on a non-suckering shrub that grows to over 5' tall. The black fruits are often found still on the shrub when it flowers the next year.
Culture for sweet box is fairly simple. They all like a moist, well-drained soil which is high in organic matter. Full to partial shade is the optimum although they will grow in full sun. Full sun situations will almost invariably result in yellowing of the leaves, though. sweet box rarely needs pruning, but if necessary for shape, prune after flowering in mid-spring.