Convex-Leaved Japanese Holly Ilex crenata 'Convexa'

Convex Japanese holly is a small, handsome, multi-stemmed, evergreen shrub in the holly family (Aquifoliaceae). It is noted for its pea-sized black fruit and convex or bullate leaves. This cultivar is female.

Plant in the full sun to partial shade in acidic well-drained soil though it tolerates a wide range of soil types, from moist to dry. The shrub tolerates drought, shade, air pollution, poor soils, and clay soils and is easy to transplant. It may not thrive in areas with high heat and humidity (USDA zones 8 and 9). The plant has a slow growth rate, likes to be in the shade and does not like alkaline soils. This cultivar produces a heavy crop of fruit in the fall, which can rob nutrients from the leaves causing them to show signs of nutrient deficiencies. With that in mind, some people prefer to plant male cultivars of Japanese holly (e.g. ‘Stokes’) for the fall and winter evergreen foliage but not the fruit.

It is an extremely dense rounded or vase-shaped shrub that does well with heavy pruning and topiary, is very suitable for hedging and grows up to 8 feet high and twice as wide. The leaves are dark green, about 0.5 inches long, and convex when viewed from above. The leaves are usually smaller than those of 'Hetzii' or 'Latifolia'. This plant flowers in late spring, and its fruits ripen in abundance in the fall. The fruits are black and not showy.

Consider this compact shrub for mass planting or in groups. It may also be used with other foundation plantings. It is suitable for an Asian, pollinator, or winter garden.

Quick ID Hints:

• compact, dense, rounded to vase-shaped broadleaf evergreen shrub
• greenish-white inconspicuous flowers in the springs
• dark green, 0.5-inch, alternate, convex upper surface, rounded leaves with crenate margins
• small black fruits that ripen in the fall

Diseases, Insect Pests, and Other Plant Problems: Potential insect problems include spider mites, aphids, scale, and holly leaf miners. This shrub is susceptible to iron and nitrogen deficiencies. Alkaline soils will cause the leaves to turn yellow.

The Clemson Cooperative Extension Home and Garden Information Center has a factsheet on common diseases and insect pests.

VIDEO created by Ryan Contreras for “Landscape Plant Materials I:  Deciduous Hardwoods and Conifers or Landscape Plant Materials II:  Spring Flowering Trees and Shrubs” a plant identification course offered by the Department of Horticulture at Oregon State University

More information on Ilex crenata.