HARDINESS: Zones 5 to 9
PREFERRED SOIL pH: Acid
PREFERRED SOIL TYPE: Average, well-drained
PREFERRED LIGHT: Sun to partial shade
ATTRIBUTES: Evergreen foliage and abundant red fruits; for specimens
SEASON OF INTEREST: Year-round; berries in winter
FAVORITES: 'Cardinal', 'Merry Christmas', 'Old Heavyberry' for berry production
QUIRKS: Female trees need a male pollinator to set berries
GOOD NEIGHBORS: Clethra, hydrangea, pine, rhododendron, witch hazel
WHERE IT GROWS BEST: Sun or open shade in well-drained, acid soil
LONGEVITY: Lives for centuries
POTENTIAL PROBLEMS: Leaf browning from winter exposure; leaf miners, holly midges
SOURCE: Nursery plants
DIMENSIONS: To 50 ft (15.2 m) tall and 25 ft (7.6 m) wide
American Holly in the Landscape
When other trees are bare in winter, evergreen hollies laden with bright berries bring much appreciated beauty to the garden. There are many holly species in cultivation, but none can match the native American holly for its combination of classic cone shape, hardiness, and longevity.
American hollies have spiny, leathery green leaves, persistent red berries, and smooth gray bark. It grows slowly, but this species can reach SO ft (15.2 m) in height after several decades, and it may live for centuries. American hollies eventually need space to spread, but you can surround them in foundation groups or borders with shrubs of more modest proportions, such as hydrangea, witch hazel, rhododendron, and clethra.
Because hollies produce male and female flowers on separate plants, the berry-producing females need a male nearby for pollination. The gender of the plant is listed on the nursery tags, simplifying your search for the right one. A little pollen literally goes a long way when bees carry it, so one male plant growing within a few blocks of a group of females is usually sufficient. Find an out-of-the-way place in your landscape for a good pollinator which will have attractive foliage, but no berries, such as 'Jersey Knight' or 'Isaiah'.To avoid an unbalanced look when planting hollies in groups, make them all the same gender. In addition to producing berries, some females are a bit hardier. Look for 'Amy', 'Cardinal', 'Merry Christmas', and 'Old Heavyberry' if you garden in Zone 5, at the northern edge of American holly's hardiness range.
Other Care-Free Hollies
English holly (Ilex aquifolium) looks similar to American holly but is hardy only to Zone 6 and does best in cool, moist climates. While many varieties are grown as shrubs, 'Green Pillar' is an especially handsome upright tree, with dark green, spiny leaves and clusters of red berries. Because it needs little pruning, it is suitable for hedges, although it is also an excellent stand-alone specimen. 'J.C. van Tol' is an unusual variety with spineless leaves and it does not need a pollinator to produce berries.
For warm climates, try Altaclara holly (I.x altaclarensis), hardy to Zone 7. This vigorous grower tolerates heat, wind, drought, and salt spray and can grow 15-20 ft (4.6-6.1 m) tall. Its thick, glossy, nearly smooth leaves and heavy crops of red berries make this a valuable specimen tree.
Growing American Holly
Even though holly grows slowly, select a small specimen, which will do a better job of establishing itself in your yard for a long, happy life. Set plants out in early spring in a well-drained site that is also protected from winter weather, especially winds, which can cause leaves to brown. Hollies must be transplanted with a generous soil ball, so take care to keep it intact to prevent damaging the roots.
American hollies are occasionally bothered by leaf miners, which are small caterpillars that tunnel into leaves, disfiguring them with trails. Snip off and dispose of affected leaves and remove fallen, infested leaves to solve the problem. If green berries fail to turn red, they may be infested with holly midges. Prune off and destroy infested berries, and if problems persist, switch to a cultivar that escapes damage by blooming later in spring.