Japanese pachysandra (Pachysandra terminalis) is an extremely popular evergreen groundcover. Native to Japan and China, Japanese pachysandra enjoys widespread use primarily in the cooler regions of its range (USDA Cold Hardiness zones 5a to 8b). Another member of this genus, Allegheny spurge (Pachysandra procumbens), is a lesser-known semi-evergreen species. It is native to fertile, well-drained, moist wooded areas in Indiana, Kentucky, Tennessee, North Carolina, south to Florida, and west to Louisiana (USDA Cold Hardiness zones 5b to 9a).
Both species grow six or more inches high and spread by underground stems called rhizomes. Japanese spurge has an erect, upright growth habit and aggressively spreads laterally to create a nearly seamless mat of leaves and stems. Allegheny-spurge has a lateral, prostrate growth habit and expands radially to form distinct clumps.
In the spring the light green leaves of Japanese pachysandra emerge at the tips of its stems, which contrast well with the mature, shiny dark green leaves. At the terminal ends of its stems, one- to two-inch long spikes of white, slightly fragrant flowers open in early spring. Male and female flowers occur separately with 15 or more male flowers above and one or two female flowers below.
Allegheny spurge has a similar bloom period, but it produces one to five pinkish-colored bottlebrush spikes of fragrant flowers that arise from a petiole or leaf stalk near the base of its prostrate-growing stems. When the flower stalks are not hidden by foliage, they produce a striking two- to four-inch long bottlebrush spike of white to pinkish-white flowers. The male flowers are at the top and the female flowers, if any, are at the base of the stalk. As the flowers fade, old, mature leaves also decline and wither. New, medium-green to grayish-green leaves emerge and during the season, develop attractive light-green or gray-green blotches. In the fall and winter, the leaves turn bronze-brown, but some may develop shades of light red or purple.
Both species thrive in partial shade to full shade and prefer well-drained, fertile soils. Japanese pachysandra is well-suited for planting in shrub and tree borders to fill in gaps and connect individual beds with its uniform appearance. Small, shaded landscapes that cannot support turfgrasses can be planted with Japanese pachysandra. Because a well-managed bed of Japanese pachysandra creates a spreading, smothering blanket of foliage, it does not partner well with other desirable plants.
Allegheny spurge is a perfect fit for naturalized, woodland gardens where it can be planted en masse. Although the mature leaves will eventually slough-off, they can be removed to improve the stand’s appearance. The less aggressive nature and open growth habit of Allegheny spurge makes it a suitable companion with other shade-loving groundcovers and low-growing plants. (See HGIC 1716, Plants for Shade for more information.)
Japanese pachysandra is more prone to infection by Volutella stem and leaf blight (Volutella pachysandricola) than Allegheny spurge. This fungal disease produces tan or brown blotches on the leaves and stem cankers, water-soaked areas on the stems that turn brown, shrivel, and die. Volutella stem and leaf blight outbreaks are often due to stresses that include planting in full sun, infestations of scale insects, and winter injury. To reduce its susceptibility to this disease, plant Japanese pachysandra in the right location with suitable growing conditions and remove and discard any damaged or diseased plants.
Japanese spurge may also be affected by euonymus scale insects, spider mites, root-knot nematodes, and voles.
A less common disease, boxwood blight (Calonectria pseudonaviculata), attacks susceptible boxwoods, but also attacks both Japanese pachysandra and Allegheny spurge, which are in the boxwood family (Buxaceae). Infections produce brown to black spots on leaves and stems, which are eventually killed. When this disease is observed and diagnosed, promptly remove and discard infected plants to reduce its spread.
- ‘Cutleaf’ has lobed leaves which impart a lacy, fine-textured look.
- ‘Green Carpet’ has darker green leaves and a more compact habit than the species.
- ‘Green Sheen’ is a heat-tolerant selection with glossy green leaves; introduced by J. C. Raulston, Raleigh, NC.
- ‘Silveredge’ or ‘Silver Edge’ and ‘Variegata’ have irregular white edges or margins on the leaves. These variegated cultivars are less vigorous than the species.
- ‘Angola’ is a heat-tolerant cultivar from Angola, LA (USDA Cold Hardiness zones 5a to 9b). The young olive-green leaves are marked with prominent bands of blue-gray variegation in the center of the leaves and a smattering of splotches and flecks up to the leaf edges. Leaves eventually turn mostly green in the summer.
- ‘Silver Streak’ produces green leaves mottled with silver-white in early fall through winter. Introduced by the Mt. Cuba Center, Hockessin, DE, in 2009.
- Arnold, M. A. 2008. Landscape plants for Texas and environs. 3rd ed. Stipes Pub., Champaign, IL.
- Avent, T. Angola Alleghany Spurge. Mt. Cuba Center. 2 June 2021 <https://www.plantdelights.com/products/pachysandra-procumbens-angola>.
- Burrell, C. C. 2006. Native alternatives to invasive plants (Brooklyn Botanic Garden All-region Guide). Brooklyn Botanic Garden, Brooklyn, NY.
- Dirr, M. A. and J. H. Alexander III. 1979. The Allegheny pachysandra. Arnoldia 39(1):16-21. 2 June 2021 <http://arnoldia.arboretum.harvard.edu/pdf/issues/1991-51-4-Arnoldia.pdf.>
- Mellichamp, L. and W. Stuart. 2014. Native plants of the southeast: A comprehensive guide to the best 460 species for the garden. Timber Press, Portland, OR.
- Mt. Cuba Center. Silver Streak Allegheny pachysandra. 2 June 2021 <https://mtcubacenter.org/plants/silver-streak-allegheny-pachysandra/>.
- Snyder, P. 2020. Plant more pachysandra. Buckeye Yard & Garden Online. The Ohio State University. 2 June 2021 <https://bygl.osu.edu/node/1524>.