Ilex crenata 'Convexa'

Convexa Japanese Holly is a handsome evergreen shrub in the Aquifoliaceae family. It is a cultivar of Ilex crenata, or Box Leaved Holly, and is noted for its pea-sized black fruit and leaves, which are convex when viewed from above. It is an extremely dense 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 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 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.

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, including clay. 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 species is dioecious (meaning individual flowers are either male or female, but only one sex is to be found on any one plant, thus both male and female plants must be grown if seed is required). It is pollinated by bees and is not self-fertile.

Diseases, Insect Pests, and Other Plant Problems:

This holly is susceptible to spider mites and iron and nitrogen deficiencies. Alkaline soils will cause the leaves to yellow.

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.