Plant DetailShow Menu

Ilex crenata 'Convexa'

Phonetic Spelling
EYE-leks kre-NAY-tuh
This plant has low severity poison characteristics.
See below
Description

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 leaves. 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.

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.

Profile Video:
See this plant in the following landscape:
Cultivars / Varieties:
Tags:
#evergreen#white flowers#shrub#wildlife plant#green flowers#nectar plant#broadleaf evergreen#spring flowers#air pollution tolerant#topiary#specialized bees#rounded#pollinator plant#black fruits#Japanese garden#vase-shaped#evergreen shrub#poor soils tolerant#compact habit#sandy soils tolerant#clay soils tolerant#bee friendly#cultivar#landscape plant sleuths course
 
Cultivars / Varieties:
Tags:
#evergreen#white flowers#shrub#wildlife plant#green flowers#nectar plant#broadleaf evergreen#spring flowers#air pollution tolerant#topiary#specialized bees#rounded#pollinator plant#black fruits#Japanese garden#vase-shaped#evergreen shrub#poor soils tolerant#compact habit#sandy soils tolerant#clay soils tolerant#bee friendly#cultivar#landscape plant sleuths course
  • Attributes:
    Genus:
    Ilex
    Species:
    crenata
    Family:
    Aquifoliaceae
    Life Cycle:
    Woody
    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.
    Play Value:
    Attracts Pollinators
    Screening
    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: 5 ft. 0 in. - 6 ft. 0 in.
    Width: 6 ft. 0 in. - 14 ft. 0 in.
  • Whole Plant Traits:
    Plant Type:
    Shrub
    Woody Plant Leaf Characteristics:
    Broadleaf Evergreen
    Habit/Form:
    Dense
    Erect
    Multi-stemmed
    Rounded
    Spreading
    Vase
    Growth Rate:
    Slow
    Maintenance:
    Medium
    Texture:
    Medium
    Appendage:
    Spines
  • 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, 6a, 6b, 7a, 7b, 8a
  • 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 the fall and are not showy.
  • Flowers:
    Flower Color:
    Green
    White
    Flower Inflorescence:
    Cyme
    Insignificant
    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.
  • Leaves:
    Woody Plant Leaf Characteristics:
    Broadleaf Evergreen
    Leaf Color:
    Green
    Leaf Feel:
    Glossy
    Leathery
    Smooth
    Waxy
    Leaf Value To Gardener:
    Long-lasting
    Leaf Type:
    Simple
    Leaf Arrangement:
    Alternate
    Leaf Shape:
    Obovate
    Leaf Margin:
    Crenate
    Hairs Present:
    No
    Leaf Length:
    < 1 inch
    Leaf Width:
    < 1 inch
    Leaf Description:
    The upper surface of the leaves is glossy dark green and the underside of the leaves is dotted with blackish pellucid glands. The leaves are alternate, simple, about 0.5 inches long, rounded, convex above, and concave beneath with crenate margins. The leaf is a finger hat and small enough to fit on a fingertip.
  • Bark:
    Bark Color:
    Dark Gray
    Green
    Surface/Attachment:
    Smooth
    Bark Description:
    Smooth, gray-brown or slightly greenish.
  • 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.
  • Landscape:
    Landscape Location:
    Coastal
    Container
    Lawn
    Patio
    Recreational Play Area
    Slope/Bank
    Walkways
    Landscape Theme:
    Asian Garden
    English Garden
    Pollinator Garden
    Design Feature:
    Border
    Foundation Planting
    Hedge
    Mass Planting
    Screen/Privacy
    Small groups
    Attracts:
    Bees
    Pollinators
    Specialized Bees
    Resistance To Challenges:
    Deer
    Problems:
    Poisonous to Humans
  • Poisonous to Humans:
    Poison Severity:
    Low
    Poison Symptoms:
    Minor toxicity. Ingestion may cause vomiting, diarrhea, or other illness in humans.
    Poison Toxic Principle:
    Saponins
    Causes Contact Dermatitis:
    No
    Poison Part:
    Fruits