American Holly — More than Just a Holiday Decoration

American Holly — More than Just a Holiday Decoration

  • By Pat Chadwick
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  • December 2016-Vol.2 No.12
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  • 1 Comment

During the winter holiday season, it’s not uncommon to find oneself mindlessly humming “Deck the Halls with Boughs of Holly” or “The Holly Bears a Berry” or, perhaps, “The Holly and the Ivy.”  Why this preoccupation with holly, you ask.  These traditional English carols refer to the English holly (Ilex aquifolium), long the subject of European folklore. Because holly remained green in the dead of winter when all else appeared dead, ancient cultures believed it was imbued with magical powers.  Eventually, the holly was adopted by Christians throughout England and Europe as a symbol of Christmas.  Although the origins of much of the folklore regarding the holly tree have long been forgotten, the custom of decorating our homes with it in winter continues to the present time.

Photo Credit: hort-uconn.edu

American Holly (Ilex opaca)

The Pilgrims carried this fascination with hollies over from the old world to the new. Arriving the week before Christmas, 1620, in what is now Plymouth, Massachusetts, they found many unfamiliar plant species. However, one tree looked familiar to them — the American holly (Ilex opaca).  A welcome sight, the tree most likely reminded them of their beloved English holly.

The native American holly was used extensively in early colonial gardens.   George Washington’s ornamental garden at Mount Vernon, populated almost exclusively with native species, was no exception. An admirer of native hollies, Washington mentioned them often in his diaries.  On March 28, 1786, he noted his gratitude for a gift of holly seedlings received from Colonel “Lighthorse Harry” Lee.  The seedlings were planted that spring in the South Semicircle at Mount Vernon, where they continued to grace the estate well into the 1900s.

CHARACTERISTICS OF THE AMERICAN HOLLY   

The American holly’s natural range extends from Massachusetts south to Florida and west to Texas and Missouri.  It can look somewhat shrubby and misshapen in a woodland setting where it must compete for sunlight, space, and nutrients.  But if grown in a spacious landscape setting, this hardy, broadleaf evergreen displays dense, horizontal branching and a symmetrical, pyramidal shape.   Although slow growing, a mature specimen will eventually grow 50 feet tall on average with a spread of 18 to 40 feet.

American holly foliage is stiff, spiny, leathery, and dark to olive green. The spines are as sharp as thorns, making it a daunting task for humans to navigate through the dense, prickly foliage.  Birds, on the other hand, find its foliage the ideal habitat for nesting and a refuge from hungry predators.

In late spring, small white flowers appear all along the branches.  While not particularly noticeable to humans, the flowers attract a broad range of pollinators.  In summer, following pollination, green berries form along the branches during the summer. Technically, the berries are four-seeded drupes, or fleshy fruits surrounding a central seed or seeds.  In fall, the tree undergoes a transformation as the berries turn from inconspicuous green to glorious, crimson red.  The berries are poisonous to humans but an important food source for birds during the winter.

In his illustrated encyclopedia of hardy trees and shrubs, Dr. Michael A. Dirr describes the American holly as perhaps the “finest tree-type evergreen holly.”  Of the more than 1,000 named cultivars in existence, many of them are superior to the species in terms of habit, disease resistance, and berry production.   ‘Old Heavy Berry’ is considered to be one of the best fruiting selections of the many red-berried cultivars.  ‘Satyr Hill’ is another commonly grown cultivar.  It has the distinction of being named “Holly of the Year” in 2003 by the Holly Society of America, Inc.

While the vast majority of American holly cultivars have red berries, some cultivars have yellow or orange-red berries.  ‘Goldie’ is an example of a yellow-berried cultivar that bears an extra heavy crop of berries.  ‘Grace McCutchin’ is an example of a cultivar that bears orange-red fruit.

American holly is a dioecious plant, with staminate (male) and pistillate (female) flowers on separate plants.  In other words, a male pollinator plant must be available in order for a female plant to produce berries.

THE DISTINCTION BETWEEN AMERICAN HOLLY AND OTHER EVERGREEN HOLLY SPECIES

In addition to the American holly species, several other evergreen holly species are also native to Virginia.  Unlike the American holly, which tends to grow into a medium-size tree, the other native species are shrubs or small trees.  For example:

  • Inkberry holly (I. glabra) – This shrub form’s small, smooth, spineless leaves faintly resemble those of boxwood. Unlike other holly species, Inkberry holly produces black berries.  This plant is widely available commercially and is commonly used in foundation plantings.
  • Large Gallberry (I. coriacea) – This large 10 to 15-foot tall shrub with small, leathery leaves is similar in appearance to Inkberry. It also produces black berries that are larger than those of Inkberry. This plant is native to the southeastern tip of the Virginia coast, bordering on North Carolina, where it thrives in moist, sandy soil.  It does not hold its fruit like other holly species but drops it in late summer or fall.
  • Yaupon holly (I. vomitoria) – This large 10 to 20-foot tall shrub or small, multi-trunked tree with an irregularly branched form has small, oval-shaped shiny leaves that are slightly serrated on the margins. This species is available commercially and is generally used for hedges or foundation plantings.   This is the only native North American plant that contains caffeine.

Holly is native to every continent except Antarctica.   Many non-native species and their cultivars are widely distributed throughout the United States.  For comparison purposes, here’s how some of the more commonly grown non-natives compare with the American holly:

  • Photo Credit: wikimedia.org

    Variegated English Hollly (Ilex aquifolium)

    English holly (I. aquifolium) — This species is smaller than the American holly, topping out at around 35 feet. It has glossy, spiny leaves as opposed to the larger, duller, non-glossy foliage of the American holly. The leaves on both species have very sharp thorn-like spines on their margins.   English holly is less hardy than American holly and does not like the heat and heavy soils of the southeast United States.  The seeds of English hollies are widely spread by birds, which carry them into forested areas.  The plant roots sucker, allowing dense thickets to form.  The thickets cast deep shade, which affects nearby native vegetation.  As a result, English holly is considered to be an invasive species in the Pacific Northwest, New Jersey, and Virginia.

  • Chinese Holly (I. cornuta)
    Photo Credit: Austintexas-gov

    Dwarf Burford Holly (Ilex cornuta)

    – This 10- to 15-foot tall species is much smaller and less spiny than the American holly. Whereas American hollies are dioecious, Chinese hollies can produce berries without the benefit of male pollination. Depending on the selection, berry colors can range from red to yellow or dark orange.  The straight species of this plant is not sold in the landscape trade, but many cultivars are available, including one of the most popular, the ‘Burfordii’.  A Burford holly can be grown as a large, dense shrub or limbed up into a small tree.   A dwarf form of ‘Burfordii’, with slightly puckered leaves, grows to about 6 feet tall and 4 feet wide.

  • Japanese Holly (I. crenata) – Unlike American hollies, which have very spiny leaves, Japanese holly foliage does not have any spines. Many of the Japanese holly cultivars have dense oval shrubby forms that mimic the look of boxwood.    ‘Compacta’ is a neat, globe-shaped form of Japanese holly that grows 6 to 8 feet tall and slightly wider. ‘Helleri’ is another globe or mound-shaped cultivar that only grows to about 4 feet tall.   ‘Steeds’ is an upright, conical selection that grows to about 8 feet tall.  ‘Sky Pencil’ is a popular columnar cultivar that grows 10 feet tall but spreads less than 2 feet wide.  The Holly Society of America, Inc., named ‘Sky Pencil’ as it’s Holly of the Year in 2004.
    Photo Credit: Wikimedia Commons

    ‘Sky Pencil’ Japanese Holly (Ilex crenata)

CULTURE AND GROWING CONDITIONS

American hollies thrive in USDA Zones 5 to 9 and are adaptable to a broad range of site conditions, including sandy, loamy, or clay soils.  For best success in growing American holly, buy a balled and burlapped or containerized plant rather than a bare-root specimen, which may not transplant as well.  Avoid digging up holly specimens from the wild, as they don’t ordinarily transplant very well.

The planting site should be sunny or partially shady.  While hollies can tolerate a fair amount of shade, they will grow better and bear more berries if grown in full sun. Too much shade will result in a more open, leggier habit with fewer flowers and a diminished fruit production.  Site it well, since it can live for more than 100 years.

The soil should be slightly acidic (with a pH ranging from 3.5 to 6.0) and moist but well-drained.  Hollies don’t like soggy soil.  Once established, American hollies can thrive in a site with dry soil, although it does appreciate a little supplemental water in really dry conditions.

In colder, northernmost areas of its range, American holly does best if planted in a site that provides shelter from the wind in winter.  Frigid, drying north winds can desiccate the leaves, causing them to turn brown, and kill the twigs and branches.   While this can stress the tree, it will produce new leaves in spring.

Plant both a male and a female of the same species that bloom at the same time.  For best berry production, position the two plants within 40 feet of one another.  One male is generally sufficient to pollinate three female trees.

AMERICAN HOLLY PESTS, DISEASES AND OTHER PROBLEMS

American holly is subject to a number of fungal diseases but few actually threaten the health of the tree. Root rot can be a problem if the soil is soggy and does not drain well.  Holly Leaf miner (Phytomyza ilicicola) and holly scale (Asphondylia ilicicola) are the worst of the insect pest problems.

Deer browse can be an issue in winter when food is scare.  However, the prickly foliage will generally keep browse damage to a minimum.  While birds are the primary consumers of the berries, deer, squirrels, and other small mammals will eat them as well.

USES FOR AMERICAN HOLLY IN THE LANDSCAPE

Use American holly as a focal point in the landscape, giving it plenty of room so that it can be enjoyed as a specimen tree.  It also works as a vertical accent in a large-scale mixed border.   It responds well to pruning and, thus, can be used to create a tall hedge or a screen. Keep the mature size in mind when spacing the trees apart.

American holly species and their cultivars are easy to grow, drought tolerant, generally deer resistant, a favorite of many pollinator insects, and require little or no maintenance.   While attractive all year round, they are especially appreciated in the winter garden where most other plants are dormant and the color green is largely absent.

SOURCES

A Natural History of Trees of Eastern and Central North America (Peattie, Donald Culross, 1948)

Dirr’s Hardy Trees and Shrubs, An Illustrated Encyclopedia (Dirr, Michael A., 1997)

Founding Gardeners (Wulf, Andrea, 2011)

“Evergreen Hollies (Ilex spp),” Virginia Cooperative Extension Publication 3010-1482 (pubs.ext.vt.edu/3010/3010-1482

“American Holly,” University of Kentucky College of Agriculture, Food and Environment website uky.edu/hort/American-Holly

“Aquifoliaceae Ilex opaca,” Virginia Tech Department of Forest Resources and Environmental Conservation Website, American Holly Fact Sheet

“Problem Plant:  English Holly,” Master Gardeners of Northern Virginia website mgnv.org/reading-room/problem-plants

Holly Society of America website (hollysocam.org)

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