Sarcococca hookeriana var. digyna, commonly known as sweet box purple stem, is a perennial shrub that produces white flowers and purple stems or shoots. As an evergreen ground cover, sweet box is a welcome addition to many landscapes. Native to the Himalayan and Afghanistan regions, the ideal climate for this plant exists within USDA Hardiness Zones 7 to 9.
Sweet box typically grows between 1-and-2 feet tall but is able to reach heights between 4-and-6 feet. According to the University of Delaware, "Sweet box is a dense, evergreen shrub that spreads by stolons and develops into a colony" producing "black berries and lustrous green foliage." Young shoots of sweet box appear in shades of purple. Most sweet box leaves grow from 2-to-3.5 inches long.
Sweet box produces tiny, fragrant, white flowers from February through April in zones 6 to 9. If grown in colder zones, sweet box will bloom in that particular zone's early spring months but may not be hardy enough to survive the climate for long.
Sweet box historically has been used as a ground cover and is favored because it does not spread aggressively and can be contained. It works well when needed on a large-scale level. Its sweet fragrance, from which it derived its name, provides a lovely scent to any garden or landscape, and the white flowers add interest and color.
Choose a well-drained site in the shade for planting sweet box. Add organic matter to an acidic and moist soil for best results. Work the soil to a depth between 8-and-10 inches. Sweet box, as with other ground covers, should be planted during the fall to take advantage of the rains and cool temperatures of that season. Do not space the plants too far apart since this can encourage weeds. Before sweet box is firmly established, which takes about two years, weed control is a primary concern.
Sweet box grows best in partial to full shade. If grown in the sun, it becomes yellowish in color, and foliage may burn. Soil that is not acidic will result in light green foliage. It has a slow-to-moderate growth rate. Sweet box is typically not disturbed by pests and is drought tolerant. The low maintenance requirements of this plant make it a favorite for beginner gardeners or those who are limited in the amount of time they can dedicate to a garden.