ASK THE MASTER GARDENERS
Q: I planted a low, spreading Himalayan sweet box in a dry, mostly shady area between a sidewalk and a garage that previously had supported pachysandra. I understand that the sweet box requires a fair amount of water, especially during hot weather. The mostly clay soil has been amended with topsoil over the years and is covered with a layer of fine pine mulch. Would you suggest any soil treatment?
A: Himalayan sweet box is a shade-loving evergreen that will grow in low-light conditions that other shrubs cannot tolerate. These plants form an attractive ground cover that produces fragrant white flowers that are mostly concealed by the foliage in late winter.
Established plantings of sweet box (Sarcococca hookeriana var. humilis) will tolerate slightly alkaline soil and drought, but grow best in moist, slightly acidic soil that is rich in organic matter.
As you renew the mulch from year to year, you will build organic matter in your soil. “Topsoil” may have various origins and is not standardized. Some loads of topsoil may contain adequate organic matter to support plant growth, but other loads may not.
As long as your plants appear dark green and healthy you should not have to make any additions to the soil. If the plants look off-color, they may be exposed to too much sun. If this is not the case, you could test the soil and make amendments as indicated by the results.
(photo by Alexis Alvey, via Margery Daughtrey)
One caveat regarding this handsome plant: it is related to common boxwood and is susceptible to boxwood blight. If you have valuable, healthy boxwood on your property, you may want to avoid introducing sweet box nearby.
For more information on soil testing contact your local Cooperative Extension.
Amy Albam, Community Horticulture Educator, Cornell University Cooperative Extension of Westchester