Holly isn’t just for holidays – the huge holly family (Ilex) includes a wide variety of plants that make great screens, hedges or specimen plants in the home garden all year.

Just don’t plant English holly (Ilex aquifolium), the species with the dark, glossy leaves and bright red berries that most people picture when they hear the word “holly.” This non-native species has become invasive here and isn’t recommended for home gardens (see box for more information), so leave it to the professional growers.

But that still gives gardeners about 400 species of holly to choose from, and many can be seen at the Washington Park Arboretum in Seattle, which has the second-largest holly collection in the U.S.

“Our U.S. native Ilex opaca (American holly) and its many cultivars are underutilized and in many cases better ornamentals than (the) Ilex aquifolium counterparts,” said David Zuckerman, horticulture staff supervisor at the arboretum, which is part of the University of Washington Botanic Gardens.

Like American holly, some hollies have the “traditional” holly look, while other holly species display different charms.

One of Zuckerman’s favorites is the deciduous Ilex verticillata. Although the plant’s oval leaves drop in the fall, “the berries persist through winter and can really liven up the winterscape,” he said.

Japanese holly (Ilex crenata) is a family of “quite handsome shrubs” with small evergreen leaves and black berries, Zuckerman said. These hollies look more like boxwood than holly, and lend themselves to hedging and topiary. “I really enjoy some of the whimsical dwarf-forms,” he said, such as Sky Pencil, which grows 6 to 8 feet tall but just 12 to 18 inches wide, adding a vertical accent to the landscape.

When adding holly to the garden, remember that hollies are dioecious – both male and female plants are needed for the female to produce berries, Zuckerman said. Good companion plants for evergreen hollies include deciduous choices like witch hazel, lindera (spicebush) and corylus (filbert), Zuckerman said. And Asian plants such as Japanese maple and bamboo can partner well with the more formal-looking Japanese hollies, he said.

HOLLY CARE

Holly plants not only add texture and color to the garden, but also they’re easy to grow.

Soil: Most hollies like rich, slightly acid soil that is consistently moist but well-drained.

Exposure: All types can take some shade, but plant in full sun for best berry production and most-compact growth.

Planting: Be sure to plant male and female hollies of the same species so the female plant produces berries. Only one male plant is needed to pollinate all females of the same species.

Pests/diseases: Hollies typically aren’t bothered by serious pests and diseases. A fungal leaf and twig blight has been a recent problem at the arboretum, but it usually subsides during the dry summer months. More common are scales and a sooty mold that doesn’t feed on the plant but produces a black layer on top of the leaves.

Treatment: Wipe off sooty mold. Control scale with insecticidal soaps and horticultural oils. For fungal diseases, practice good sanitation – remove dead branches, pick up leaves where the fungus can overwinter, and mulch the area.

Holly profiles

Ilex opaca

Common name: American holly

Form: Pyramidal or rounded tree

Foliage: “Traditional” spiny holly leaves, but duller green above and yellow-green beneath.

Berries: Usually red

Size: Depending on variety, slow growing to 40-50 feet tall and 20-40 feet wide

Try this: “Canary” has vivid yellow berries.

Ilex pedunculosa

Origin: China, Japan

Form: Shrub or tree

Foliage: Oval, smooth-edged

Berries: Red, each carried at the end of a long fruit stalk (peduncle)

Size: 15-20 feet tall, 12-15 feet wide

Ilex verticillata

Common names: Winterberry

Form: Shrub

Foliage: Deciduous oval leaves

Berries: Red, persisting through winter

Size: 6-10 feet tall; spreads wider

Try these: “Afterglow” has orange-red berries, “Cacapon” bears dark-red berries, “Red Sprite” is a dwarf growing 3 feet tall and wide, with larger red fruit.

Ilex crenata

Common name: Japanese holly

Form: Dense shrub

Foliage: Small, finely toothed leaves

Berries: Black

Size: Typically 4-10 feet tall and wide

Try these: “Convexa,” growing 5-6 feet tall and 8-10 feet wide, is good for hedging or screening; “Mariesii” grows 2-3 feet tall by a foot wide in 10 years, adding a vertical accent to the garden.

INVASIVE ENGLISH HOLLY

English holly (Ilex aquifolium) is commonly found in Northwest gardens, but this non-native is now considered invasive here.

Non-native plants can create problems because “they lack flora, fauna and climate-related inhibitors that would normally keep them in check in their native habitats,” said David Zuckerman, horticulture staff supervisor at the Washington Park Arboretum in Seattle, part of the University of Washington Botanic Gardens.

In Washington, English holly “has escaped cultivation and is spreading rapidly into our natural lands,” Zuckerman said.

His advice to home gardeners: Remove any English holly, and replace it with noninvasive substitutes.

The Washington Invasive Species Coalition – in collaboration with state and county governments, the nursery industry and nonprofit conservation groups – recommends these substitutes for English holly.

Meserve hybrid hollies (Ilex x meserveae)

Features traditional holly foliage, red berries and a dense habit perfect for hedges and screening. Grows to 15-18 feet or less. Both male and female plants are needed for the female to set berries.

Tall Oregon grape (Mahonia aquifolium)

Has dark green, hollylike leaves, with a dense, upright habit. Sports bright yellow blooms in early spring, followed by blue-black berries in summer. Reaches 8-10 feet tall over time.

Holly-leafed osmanthus (Osmanthus heterophyllus)

Looks like an English holly without berries; has small but very fragrant flowers in autumn. Its densely branched, upright habit is well-suited to screening and hedges. Grows 15 feet or taller.

For information, visit www.invasivespeciescoalition.org.

Source: David Zuckerman, Washington Park Arboretum