Japanese ardisia (Ardisia japonica), also called marlberry, is an evergreen groundcover introduced from Japan and China. It is a low-growing, woody shrub that typically grows to a height of 8 to 12 inches. It spreads slowly by rhizomes at the rate of about 6 inches per year to approximately 3 feet wide. As it spreads, it makes a dense mat of foliage. Japanese ardisia grows best in moist, but well-drained, acidic soil, and in partial to full shade. Excess afternoon sun may cause foliar burn. Mature foliage is dark green, but new growth in the spring may be light green, copper or bronze. Leaves are thick, glossy, leathery, and the margins are finely serrate.
Small, pale-pink flowers are formed in racemes beneath the new season’s foliage. These flowers are about ½-inch long, star-shaped and in small groups. Buds first appear in June, and flowers are present during July and August.
The fruit are ¼-inch, bright red drupes, quite similar to miniature cherries in shape. A drupe is a fruit with a fleshy outer portion which surrounds a hardened pit or stone containing the seed. The fruit appear in September and are nestled among the foliage. They mature by October or November and persist throughout the winter.
Japanese ardisia is an excellent plant for a shady or partly shady woodland garden to fill in as a groundcover. Although it will grow in low light areas where turfgrass will not, it does not tolerate foot traffic. It slowly spreads by suckering but is not considered aggressive. It does not tolerate standing water, but is not extremely drought tolerant. Therefore with tree root competition, it may require weekly irrigation during the summer drought. Soils should be slightly acidic between 6.0 and 6.5. Apply a light covering of mulch, such as pine straw, in the early spring before new foliage is produced. Japanese ardisia is considered a deer resistant plant and is generally not troubled by diseases or insect pests.
Japanese ardisia grows best in USDA cold hardiness zones 8 and 9. Cold winter temperatures in the low 20’s will burn the foliage of Japanese ardisia if plants are not given cold protection, such as being planted beneath the overhanging branches of evergreen shrubs. New foliage may also be injured by late spring frosts.
Covering the plants with a thick layer of pine straw will give added protection down to the upper teens, but the mulch layer needs to be removed as soon as cold weather has passed. Variegated cultivars are less cold hardy than green leaf forms.
- ‘Hakuokan’ is a variegated form with gray-green foliage and wide, white leaf margins.
- ‘Ito-Fukurin’ is a variegated form, also with gray-green foliage, but thin, white leaf margins.
- ‘Nishiki’ has rosy-pink variegated leaves on new growth, which turns to a yellow margin with leaf maturity.
- ‘Hinode’ is a variegated form with a broad band of yellow variegation in the center of each leaf.
- ‘Chirimen’ may be a more cold tolerant green form, as it is listed as growing in USDA Cold Hardiness Zones 6 – 9.
- ‘White Cap’ is a variegated form with gray-green foliage and thin, white leaf margins.
Reversion of a variegated form to green leaves may be a problem. Typically, if any variegated plant reverts, the green portion tends to outgrow the variegated parts of the plant.
Japanese ardisia may be propagated by division, cuttings or seed. Because of the spreading nature of the plant, it is quite easy to dig a clump and replant or pot the division.
It can be easily propagated using 4-inch terminal cuttings taken between June and September. Remove the lower leaves from each cutting and treat the cut ends with a rooting powder or liquid. A rooting hormone containing IBA stimulates root formation best. Examples of powdered products containing IBA are Miracle Gro Fast Root Rooting Hormone, Ferti-lome Rooting Powder, Bonide Bontone Rooting Powder, GardenTech Root Boost, and Garden Safe Take root Rooting Hormone.
Fill new or cleaned 4-inch containers with a well-drained medium made of a 1:1 mix of perlite and potting soil. Stick one treated cutting into each container, water to settle the soil mix, and cover the containers with clear plastic bags to keep relative humidity high. Place pots in a warm site with bright indirect light. Cuttings should be rooted in 4 weeks.
The fruit and seeds mature in the fall during November. Seeds do not need a cold, moist stratification. Seed may be cleaned of the fleshy fruit coat and stored dry until spring. Plant outside once the last spring frost has passed.
Related Invasive Species
A close relative of the Japanese ardisia is the coral ardisia (Ardisia crenata), which is a small, upright, evergreen shrub that grows to six feet tall. This species is more cold sensitive, but will grow well in USDA zones 8 to 10. It will be killed back by a hard freeze, but may re-sprout from its root system. Ardisia crenata goes by several additional common names, such as coralberry, spiceberry, and Christmas berry. The latter name arises because the bright red berries typically remain on the plant through the winter season, until eaten and spread by raccoons and birds, such as the cedar waxwing. They hang down in clusters, and each of the red ¼-inch fruit contains one hard seed that maintains high viability over a long period. A white-fruited variety is also in cultivation.
Coral ardisia is considered an invasive plant as close by as in Northern Florida, and because of the mild winters of recent years, there is the potential that it could easily colonize sites along the coast in South Carolina. It will flourish in woodland settings and is quite tolerant of soil type and pH.
Young plants from dispersed seeds will produce their fruit in as early as two years. As plants mature, they produce a rhizomatous root system, which will result in clumps of numerous plants.
Control by pulling generally results in new sprouts from the remaining and extensive root system. Sprays with 3% glyphosate or triclopyr can control the coral ardisia.