American holly (Ilex opaca var. opaca*) of the Holly (Aquifoliaceae) family is a broad-leaf evergreen tree frequently used for Christmas decorations. In the U.S., it occurs from Texas to Illinois east to Massachusetts and thence south and east to the Atlantic and Gulf Coasts. The genus name comes from scientific name for holm oak (Quercus ilex), which has broad evergreen leaves. The specific epithet “opaca” is a Latin word meaning dull or opaque (referring to the leaves), not glossy or transparent, in contrast to European species. In Arkansas, American holly is found throughout much of roughly the southeastern two-thirds of the state. In its native habitat it is found mainly in the understory of hardwoods and pines in moist, well-drained soils of rich lowlands, stream terraces, on northern slopes and along swamp margins. Other common names include Christmas holly, white holly (for its wood color), and evergreen holly.
American holly may reach 40 to 50 feet tall and, occasionally, taller**. Trees generally have a straight central trunk 1 to 3 feet in diameter, with several main branches in mid to upper portion. New spring branches, straight and slender, with minute short pubescence, are green at first, becoming light gray at the end of the growing season and, thereafter, a darker gray with lighter, often silvery blotches. With short, stout, stiff and crooked branches with similar growth rate along its entire height, trees are typically pyramidal with a rounded top. Young trees in full sun, which have branches to the ground, tend to be compact and densely branched while those in more shady settings have fewer branches and a more open structure. With age, lower portions of trunks becomes branch-free and upper branching becomes more open. Trunks have thin, gray bark that is usually smooth. Growth rate varies from slow to moderate, depending on habitat quality. American holly can survive Arkansas’s harshest winters, but does not survive fire or long-term soggy soils.
Photo 1: Thin bark may be smooth or rough. Trunk diameter of a young tree at left is 5 inches while diameter of tree on right is 1 foot 9 inches.
American holly has evergreen leaves that appear in early spring and drop off two springs later, about a month after new leaves have appeared. New spring leaves are a bronzy green that quickly changes to a medium green. Mature leaves have a slightly shiny upper dark green surface and a dull yellowish green lower surface. Leaves, alternate and elliptical in general outline, have thick stiff blades that range from 2 to 4 inches long and half as wide. Leaves bow-up from mid-rib to blade margins so that the blade is an elongated “bowl” (top convex and bottom concave), with a slightly billowy blade surface between secondary veins. The blade is stout enough that when the upper surface is pressed down, it springs back to its original shape. Blade margins typically have straight, sharp, stout, well-spaced, outward-pointing, sixteenth-inch, light-colored spines, along with an equally-sized spine at leaf apex. When spines are present, 3 to 6 pairs typically mirror across mid-rib. Narrowly revolute (turned under) leaf margins are wavy, when seen from above, with a spine tipping each wave. Bases of leaves are rounded to wedge-shaped. Petioles are relatively short at about ½ inch long on four-inch-long leaves. Upper mid-rib is boldly channeled and light colored while the mid-rib of lower surface is prominently exserted and light colored. Secondary, closely-spaced pinnate veins are obscure.
Photo 2: In spring, bronzy leaves grow from new green branches while dark green leaves from previous spring remain on gray branches. Yellowing leaves in background, about to drop, grew two years earlier. Photo taken mid-April.
American holly is dioecious (female and male flowers on separate trees). Female flowers typically occur singly on pedicels, but in groups mostly below terminal leaves of new twig growth. Fragrant male flowers occur in cymes comprising up to eight flowers, often in elongate clusters, from axils of current or previous years’ leaves or directly from current year’s stems. Inflorescences growing directly from new stems are subtended by elongate, weak bracts that quickly drop. Female and male flowers, of about the same size (¼ inch diameter), have four equally sized, spreading, white petals with cupped-tips. Female or pistillate flowers have four white infertile stamens positioned around a prominent ovary, while male or staminate flowers have four fertile stamens positioned around a small rudimentary pistil. Anthers of female flowers are tipped with a flattened white flange. Fertile oblong anthers of male flowers, bearing yellow pollen, face inward (introrse). Stamens of male and female flowers are positioned between the petals. Barrel-shaped bright green ovaries of female flowers have large, round, flattened, convex, yellow-green and sessile (no styles) stigmas. Petals are set in a small, pale green, four-lobed, persistent calyx.
Photo 3: These male flower buds, in cymes or cymose clusters, grow from old leaf axils, from new leaf axils, or directly from new stems. Leaves in the inflorescence typically have few spines. Photo taken late April.
Photo 4: Female flowers typically grow singly on pedicels but in groups positioned mostly below terminal leaves of new twig growth. Infertile stamens are tipped with an infertile flange. Photo taken first of May.
Photo 5: Display shows pistillate (female) inflorescence on left and staminate (male) inflorescence on right. Note infertile stamens of female flowers and infertile ovary of male flower.
Female trees produce round to slightly oblong, berry-like fruits (drupes) on short spindly stalks attached directly to branches. Immature green fruits mature to a low-gloss red (occasionally yellow) in November. Showy mature, firm fruits, ¼+ inch in diameter, contain four to six nutlets grouped into a circular shape, like the sections of citrus fruits. Red (or yellow) skin of fruit encloses dry yellowish pulp. Relatively small, persistent, four-sided calyxes are set tight against the fruit. The surface of light-tannish, three-sided (one rounded side and two flats sides) nutlets have longitudinal ridges. Fruit remains on trees through winter, unless eaten by birds. Nutlets are dispersed by local and migrating birds and small mammals.
Photo 6: Display of upper and lower leaf surfaces and fruits. Remnants of calyxes persist at base of fruits as a small yellowish square. Note obscure secondary pinnate veins and small terminal bud. Photo taken mid-December. Inset shows occasional yellow fruit.
With its outstanding winter characteristics (green leaves and red fruit), American holly is often planted in the home landscape. When sufficient space allows for a large tree and its spiny leaves would not be a problem, the tree should be welcomed in a natural area or woodland garden. As broadleaf evergreens, both male and female trees are great winter accent plants, especially showy on a snowy day. Fruits are an important winter food for many song and game birds and small mammals. For a “clean” trunk, lower limbs may need to be removed.
Photo 7: Mature trees in home landscapes.
- A second variety of American holly, native to the U.S., is Shrub or Dune Holly (Ilex opaca var. arenicola). It occurs in dry sandy sites in Florida.
** Arkansas’s Champion Tree, in White County, is 63 feet tall with a diameter of more than 4 feet.
Article and photographs by ANPS member Sid Vogelpohl