December Weed of the Month: Invasive Holly

Holly Collecting

Boys collecting holly and mistletoe to sell (1959) (Photo courtesy: Geoff Charles Collection at the National Library of Wales)

December is the month when many people deck the halls with boughs of holly. Sadly, invasive holly can spread, harming native plant and animal communities.

Reflecting many old traditions, holly branches are still hung today, coiled into ornate wreaths for front doors, or included in festive holiday bouquets.

For many people, the shiny, dark green leaves and red berries of holly are synonymous with the holiday season. This popular plant, however, is not native to Oregon. As European’s moved to North America, they brought with them their traditions, including holly.

Holly isn’t noxious but it is invasive

injurious to public health, agriculture, recreation, wildlife

Because of the cultural significance of holly, it is actively cultivated in our region. Holly is not regulated as a state-listed noxious weed. It can legally be cultivated and sold within Oregon.

The term noxious refers to weeds classified by the Oregon State Weed Board to be “injurious to public health, agriculture, recreation, wildlife, or any public or private property.” This regulatory designation limits the sale and distribution of a plant.

Very few culturally and economically significant species receive the noxious weed designation. Although not listed as noxious, holly is widely recognized as an invasive plant in our region.

Why is holly a problem?

Holly infestation

Holly infestation dominating a forest understory in Clackamas County (Photo Courtesy: Samuel Leininger, Clackamas SWCD)

Although not a state-listed noxious weed, holly is naturalizing and spreading throughout our area. Coniferous forests are particularly susceptible to invasion. Invasive holly competes with native shrubs and can suppress the natural regeneration of forest trees over time.

Natural resource managers across the Pacific Northwest spend considerable resources to treat and control holly in an effort to preserve native forests.

Holly seeds are spread by birds and animals who eat the plant’s red berries and then distribute the seeds over large areas in their droppings. This allows the plant to spread near and far.

Removing holly from your property

Because of its invasive nature, Clackamas County property owners are encouraged to remove holly plants. Replace them with non-invasive alternatives whenever possible. The GardenSmart Oregon guide to non-invasive plants lists lists many ornamental and native alternatives that provide similar function and appearance.

We encourage growers who are actively cultivating holly to consider phasing out production. This will help to protect your agricultural operations from losses if holly becomes listed as noxious weed in the future.

It is easiest to remove holly when the plants are small, when they can be easily hand pulled or dug up. All parts of the root need to be removed to limit re-growth, and the area should be checked regularly to remove any new sprouts.

Removal of larger plants may not be feasible and could cause extensive soil disturbance and erosion. Under these conditions, a cut-stem approach that utilizes a combination of mechanical and chemical control is more effective and may be less damaging to a site.. For additional information, contact the District’s WeedWise program at 503-210-6000.

Clackamas County residents interested in removing holly from their property may also check out one of the District’s tools from our the equipment library free of charge.

Happy Holidays and Happy Weed Pulling!
Report Weeds!
Early detection is the key
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