Ilex crenata 'Convexa'
Common Name(s):
- Phonetic Spelling
- EYE-leks kre-NAY-tuh
- This plant has low severity poison characteristics.
- See below
- Description
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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
- Profile Video:
- See this plant in the following landscape:
- Cultivars / Varieties:
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- Tags:




- Cultivars / Varieties:
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- Tags:
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Attributes:
- Genus:
- Ilex
- Species:
- crenata
- Family:
- Aquifoliaceae
- Life Cycle:
- Perennial
- Woody
- Recommended Propagation Strategy:
- Seed
- Stem Cutting
- Country Or Region Of Origin:
- East Nepal to Temperate East Asia, Japan and Korea
- Fire Risk Rating:
- medium flammability
- Wildlife Value:
- The small fragrant flowers attract bees. Members of the genus Ilex support the following specialized bee: Colletes banksi.
- Particularly Resistant To (Insects/Diseases/Other Problems):
- Moderately resistant to damage by deer
- Edibility:
- Use caution. Human ingestion of berries can cause minor toxic reaction.
- Dimensions:
- Height: 6 ft. 0 in. - 8 ft. 0 in.
- Width: 6 ft. 0 in. - 14 ft. 0 in.
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Whole Plant Traits:
- Plant Type:
- Shrub
- Woody Plant Leaf Characteristics:
- Broadleaf Evergreen
- Habit/Form:
- Dense
- Erect
- Multi-stemmed
- Spreading
- Growth Rate:
- Slow
- Maintenance:
- Medium
- Texture:
- Medium
- Appendage:
- Spines
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Cultural Conditions:
- Light:
- Full sun (6 or more hours of direct sunlight a day)
- Partial Shade (Direct sunlight only part of the day, 2-6 hours)
- Soil Texture:
- Clay
- High Organic Matter
- Loam (Silt)
- Sand
- Soil pH:
- Acid (<6.0)
- Neutral (6.0-8.0)
- Soil Drainage:
- Good Drainage
- Moist
- Occasionally Wet
- Available Space To Plant:
- 3 feet-6 feet
- NC Region:
- Coastal
- Mountains
- Piedmont
- USDA Plant Hardiness Zone:
- 5b, 5a, 6b, 6a, 7b, 7a, 8a, 8b
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Fruit:
- Fruit Color:
- Black
- Display/Harvest Time:
- Fall
- Fruit Type:
- Berry
- Drupe
- Fruit Length:
- < 1 inch
- Fruit Width:
- < 1 inch
- Fruit Description:
- Abundant globose, berry-like black drupe that is slightly greater than 1/4 inch in length. Only female plants have fruits. Fruits ripen in fall and are not showy.
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Flowers:
- Flower Color:
- Green
- White
- Flower Inflorescence:
- Cyme
- Flower Value To Gardener:
- Fragrant
- Flower Bloom Time:
- Spring
- Flower Petals:
- 4-5 petals/rays
- Flower Size:
- < 1 inch
- Flower Description:
- Non-showy greenish white flowers in spring that form in clusters of 2 to 3 and are 1/4 inch in length. Flowers bloom in late spring. Pistillate cyme, in leaf axils of current season's growth; staminate solitary in leaf axils of current season's growth.
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Leaves:
- Woody Plant Leaf Characteristics:
- Broadleaf Evergreen
- Leaf Color:
- Green
- Purple/Lavender
- Leaf Feel:
- Glossy
- Leathery
- Smooth
- Waxy
- Leaf Value To Gardener:
- Long-lasting
- Leaf Type:
- Simple
- Leaf Arrangement:
- Alternate
- Leaf Shape:
- Elliptical
- Lanceolate
- Oblong
- Obovate
- Leaf Margin:
- Crenate
- Serrate
- Hairs Present:
- No
- Leaf Length:
- < 1 inch
- Leaf Width:
- < 1 inch
- Leaf Description:
- Leaves are glossy black-green in color and the underside of the leaves are dotted with blackish pellucid glands. The leaf is too small to fit on a fingertip (around a 1/2 inch in length), and is crenate and convex.
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Bark:
- Bark Color:
- Dark Gray
- Green
- Surface/Attachment:
- Smooth
- Bark Description:
- Smooth, gray-brown or slightly greenish.
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Stem:
- Stem Color:
- Brown/Copper
- Green
- Stem Is Aromatic:
- No
- Stem Surface:
- Hairy (pubescent)
- Stem Description:
- Stems are green on current season of growth and turn gray-green to gray-brown by year 2 or 3. Young stems are often densely pubescent.
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Landscape:
- Landscape Location:
- Coastal
- Container
- Lawn
- Patio
- Recreational Play Area
- Slope/Bank
- Walkways
- Landscape Theme:
- English Garden
- Pollinator Garden
- Design Feature:
- Border
- Foundation Planting
- Hedge
- Mass Planting
- Small groups
- Attracts:
- Bees
- Pollinators
- Specialized Bees
- Resistance To Challenges:
- Deer