Ilex crenata 'Convexa'

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

It is an extremely dense rounded to a 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. This female plant flowers in late spring, and its fruits ripen in abundance in the fall. The fruits are black and not showy and the leaves are usually smaller than the 'Hetzii' or 'Latifolia' cultivars.

The genus name, Ilex, is derived from the Latin name Quercus ilex for the holm oak. This refers to the foliage similarities of the holm oak and many of the shrubs of the Ilex genus. The specific epithet, crenata, refers to the crenate leaf margins. The cultivar name, 'Convexa,' refers to the leaf appearance.

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. The female plant does produce a heavy crop of fruit in the fall, which can discolor the foliage. With that in mind, some people prefer to plant male Convexa Japanese Holly for the fall and winter foliage, but not the fruit.

The species is dioecious and both male and female plants must be grown to produce fruit. It is pollinated by bees and is not self-fertile.

Consider this compact shrub for mass planting or in groups. It may also be used with other foundation plantings.

Seasons of Interest:

Bloom:  Spring                     Foliage:  Year-round             Fruits:  Fall 

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
• female shrub has 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 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.