Ilex opaca (American Holly)


Michael's Opinion

An excellent specimen plant and is often used for hedging. Brilliant Christmas themed colours make Ilex opaca popular in the holiday season. Widely considered one of the most interesting Holly trees by gardeners, because of its dense pyramidal shape. Since the berries on the female plants are the most sought after feature of Ilex opaca, grouping or planting in windbreaks or hedges is optimal as one male pollinate up to three females.

Botanical Information

FamilyAquifoliaceae
GenusIlex
Speciesopaca
CategoryWoody
TypeTree (evergreen)
ReferencesDirr, Michael A. Dirr’s Encyclopedia of Trees and Shrubs. Portland, Oregon: Timber Press. 2011. Rodd, Tony, and Geoff Bryant. Plant Finder. Richmond, Ontario: Firefly Books Ltd. 2007
OriginIlex opaca originally was used as a representation of friendship in the winter solstice celebrations. Today, because of its shiny green foliage and red berries, Ilex opaca is a representation of Christmas celebrations, and is often brought indoors for the holiday.
Pronunciation

Details

USDA Hardiness Zone5 - 9
USDA Hardiness Ref.
Canadian Hardiness Zone5a - 8a
Canada Hardiness Ref.
RHS Hardiness Ref.
Temperature (°C)-26- ( -4)
Temperature (°F)-14 - 24
Height15 m
Spread10 m
GrowthMedium
Flowering PeriodApril, May, June

Description and Growing Information

General DescriptionDense pyramidal shape with elliptic, dark green, spiked leaves. Female plants have an abundance of orange to red berries in autumn.
ID CharacteristicThe plants most notable features are the orange - red berries that appear on female plants, and the deep green, spiked foliage.
ShapeThe tree has a densely pyramidal shape.
LandscapeIlex opaca is often used in groupings or as a specimen plant and is widely considered one of the nicest Holly trees because of its dense pyramidal form, myriad of red berries and lustrous green foliage.
PropagationSeed propagation is quite common, the embryos require further maturing and must experience a 60 day warm period at 20 °C, after which the seed begins to germinate. I. opaca will root adequately through hardwood cuttings in autumn to the middle of winter. It is beneficial to collect cuttings from a plant that has a dark terminal bud as it has reached full maturity and will root with more success.
CultivationIlex opaca thrives in acid soil in full sun, however it will tolerate partial shade. The plant prefers well drained, moist, loose, organic rich soil and is tolerant of road salt and pollution but will not tolerate harsh winds.Ilex opaca requires no regular pruning.
PestsIt may be susceptible to many pest and diseases, the most prominent being scale and leaf miner, but also including red mite, leaf spots, canker, tar spot, twig dieback and powdery mildew.
HabitatIlex opaca thrives in most soils, however it does best in soils that are moist, loamy, and well-drained. It prefers acid soil and is tolerant of salt and pollution.
Bark/Stem DescriptionI. opaca has smooth, uninteresting bark, grey in colour and often susceptible to lichens growth which does not adversely affect the plant.
Flower/Leaf Bud DescriptionThe vegetative buds on I. opaca are ovoid shaped, approximately 1.5-3 mm in length. Buds are greenish – brown in colour and lightly pubescent.
Leaf DescriptionThe leaves on I. opaca are dark green, spiked, elliptic and approximately 4 -9 cm long and 2- 4.5 cm wide.
Flower DescriptionApproximately 5 mm, dioecious, four lobed, white flowers appear on Ilex opaca from April to June, later than most evergreens. Male flowers are staminate appearing in groups of three, while female flowers are pistillate.
Fruit DescriptionThe fruit on I. opaca is round, bright red fruit and is 6- 13 mm in diameter. Ilex opaca fruit reaches full maturity in October on a 3 mm stalk and remains on female plants through the winter into the spring.
Colour DescriptionIt is notably deep green with bright orange – red berries.
Texture DescriptionIlex opaca has a medium texture.

Photographs