‘Tis the Season to Fear Holly

Contributor: Michael Ellis, M-MCPPC Park Ranger Office, Michael.Ellis@pgparks.com

With winter weather and the holiday season here, Maryland’s deciduous forests have lost their leaves, leaving evergreens strikingly bright and colorful in otherwise dormant landscapes. However, some evergreen plants now found in Maryland may be non-native invasive species. Since hollies are a celebrated symbol of December and the holiday season, the Maryland Invasive Species Council has selected non-native hollies as the December Invader of the Month.

Evergreen invasive plants such as non-native hollies can harm our forests by blanketing native plants in dense shade and a thick layer of leaf litter 12 months of the year.

Hollies are popular and attractive low maintenance plants in gardens and landscapes. Unfortunately, the berries of non-native hollies such as Chinese holly (Ilex cornuta), European holly (Ilex aquifolium), and Japanese holly (Ilex crenata) are spread by birds into Maryland ecosystems. To prevent non-native holiday decorations from spreading into your local environment, keep bright berries indoors. Seeds of non-native hollies, bittersweet, and nandina can all be spread by birds if wreaths or trimmings are left outside.

Disposal

To avoid environmental harm please dispose of non-native plant materials properly. Instead of adding these decorations to your compost pile or throwing them on the curb when you are done with them, please dispose of non-native seeds in a sealed container or consider staying warm by burning them with some logs in a wood-burning fireplace.

Identification

These non-native invasive hollies can be tricky to identify and distinguish from native hollies. Below are some photos of these species with tips to help with identification.

Chinese holly – Ilex cornuta

Chinese holly aka burford holly features dark green, glossy leaves, with pronounced spines. The leaves are usually symmetrical in appearance, with some varieties only having a single spine at the leaf tip. The leaf of Chinese holly is broadest near the tip.

European holly – Ilex aquifolium

European holly also features dark, shiny leaves, but the leaves have pronounced curly edges, and are often not entirely symmetrical in appearance. The leaf of European holly is broadest near the base or middle of the leaf.

Japanese holly – Ilex crenata

Japanese holly features very small leaves, only 1-3cm long, spines are not pronounced, the berries are black and usually go unnoticed. A good alternative to Japanese holly is our native inkberry (Ilex glabra).

Native Alternatives

If you are considering buying holiday decorations or planting a holly in your yard, please consider the environment by choosing native materials that benefit our local wildlife and the environment. American holly, inkberry, and winterberry are all native to Maryland, very attractive in the winter, and provide nutrition for birds and other wildlife during winter months.

American holly – Ilex opaca


American holly is a great alternative to invasive, non-native hollies. American holly can be distinguished  by its relatively flat, nearly symmetrical leaves that curl down slightly at the leaf tip. The leaf of American holly is usually less shiny, and broadest near the middle of the leaf. 

Winterberry holly – Ilex verticillata

Cedar Waxwings enjoying berries of native winterberry holly. Winterberry holly is deciduous, and has no leaves in the winter. Photo: Eliza Waters Creative Commons

Inkberry holly – Ilex glabra

Inkberry holly is similar in appearance to Japanese holly, however, inkberry leaves are more elongated and very flat in appearance. Photo: Rebekah D. Wallace, University of Georgia, Bugwood.org