Plants have long since solidified their importance in winter holiday traditions with well-known representatives such as the matchmaker mistletoe, bright red poinsettia, and the notable English holly. English holly, scientifically known as Ilex aquifolium, is identified by its shiny but spiky green leaves that frame vibrant red berries. This plant can grow as a shrub or a tree anywhere from 15-50 feet tall. Originally from Western Europe and brought to the United States by English settlers, English holly has become an identifiable symbol of the holidays. It has found its way into decorations, Christmas cards, and even the dense forests of the Pacific Northwest, a place where its existence has become invasive.   

Historically, English holly has been deeply rooted in Celtic traditions, where it represents fortune and has inspired the green and red holiday color palette. The plant was first brought to eastern United States as a conservation effort; however, it failed to grow properly in the east. According to King County’s Noxious Weed Blog, English holly found its way into the Pacific Northwest with its first planting in Washington state in 1891. As reported by Oregon Public Broadcasting, growing holly to sell as a festive plant became a multimillion-dollar industry in the mid- 1900s.  

Washington state became one of the world’s largest producers and exporters of holly. The crop that many families relied on for income also drew the attention of American robins, birds that began eating the red berries and dispersing the seeds throughout the state. Since then, the holly plant has found time to expand into Western Washington’s shady forests and the Cascade mountains running through Washington and Oregon due to the wet climate. Only recently have the plant’s effects on the local forests come to the attention of ecologists. Much of the research on English Holly was done at the University of Washington Bothell in 2013 by Elliot Church, a 2013 graduate, and Dr. David Stokes, a professor at the School of Interdisciplinary Arts and Sciences.   

It was found that, despite its small size, English holly can block the growth of native understory vegetation. The English holly’s tolerance to shade has contributed to slowing the growth of surrounding plants and trees and overtaking native organisms in the area, like fern and Douglas-Fir. The plant is also considered highly flammable and, if not adequately controlled, it can increase the risk of forest fires. In 2010, the Washington State Weed Control Board was presented with a proposal to label English holly as a Class C noxious weed, to control its spread and educate the public. However, farmers who grew English holly were concerned that labeling it as a noxious weed would lead to a decline in sales. With the economic consequences of environmental regulations being considered by those on the board, the proposal ultimately didn’t pass. English holly was instead classified as a “Weed of Concern,” and local governments were given authority to teach the public about its negative impacts.  Currently, English holly is considered a naturalized plant, a non-native plant that has established itself within an ecosystem, in Washington, Oregon, and California.   

              English holly secured a spot in Christmas traditions, yet its invasive nature creates ecological problems in the Pacific Northwest. The conflict between local agricultural interests and biodiversity concerns shows the need for proper approaches to manage its spread. As awareness of English holly’s impacts on local forests and wildlife grows, monitoring and removal will be crucial in protecting native habitats while respecting the plant’s significance during the holidays. Students can aid in the control of the plant’s spread by participating in community projects focused on environmental conservation or properly researching removal methods. One effective method for removing smaller holly trees is to dig around them to remove their roots. Learning how to identify the invasive species can also protect look-alike plants, such as the Oregon grape that is frequently mistaken for holly. To find more information about the English holly or learn about weed control methods, check out the King County website or the University of Washington Bothell website.