English Holly - A Friendly-looking Foe
Squak Mountain State Park has a serious English Holly infestation and Issaquah Alps Trails Club and Washington State Parks are teaming up to tackle it! We are so excited about this new partnership and are happy to announce that our first holly eradication event will be Thursday March 7. You can join and make a difference by helping to restore the park to a healthy ecosystem!
It may come as a surprise that English (European) Holly - frequently pictured in the media as a friendly, festive plant - is actually is a Class C noxious weed, and due to its hardy, prolific nature is causing significant problems in our forests. English Holly adds a dense evergreen tall shrub component to our forests that was absent before, changing the dynamics of the forest habitat. The year-round shade below the tree canopy and dense, thick growth allow holly to outcompete native plants and tree seedlings for space and resources. Once established, holly can form impassable thickets that are very difficult to remove. Wildlife have a hard time passing through its matrix of hardwood and spiky leaves.
There are many non-native plants that spread far and wide from their parent plant, but few are as difficult to control as English holly. Along with the spread of seeds, holly’s shallow root system spawns new growths through a process called suckering, in which holly fledglings, connected to their parent’s network, shoot out of the ground. Dozens of holly suckers can emerge from a single root system. Over time, some suckers develop their own root systems and strike out on their own, emerging as independent plants. Holly branches can also produce new hollies. Lower branches on taller trees often sag groundward, brushing the soil. Given enough moisture, roots can grow from just about any point of contact, supporting a new holly stem in a process called layering. If something in the woods — a falling branch or an animal — severs the connecting shoot, you’ve got a new holly tree.
Holly also grows in many local backyards! You can see some of the “suckers” near the main tree as well. Photo courtesy of Nicole Assumpcao.
It is still legal to grow and sell English Holly and there are 3 to 5 known holly farms in Washington State, as of 2022, but in the 1940s and 1950s there were over 200 holly farms in the state. In fact there used to be an English Holly and Christmas tree farm on the May Valley road near SR-900. This may have contributed to the holly invasion on Squak because in Washington, seeds from female bushes are dispersed by several species of frugivorous birds, who eat the fruit and then regurgitate the seeds in new locations. Fruits will only produce seeds if a male tree is close enough to pollinate the female flowers (with the help of bees, of course).
Holly in the forest - photo courtesy of Anne Newcomb
Washington State Parks Cascade Foothills Park Ranger Ellen Moline and I had the honor of spending a day with Henry Mustin and his restoration partner Adam Kline (former WA State Senator 37th district) on Tiger Mountain’s Tradition Plateau to learn some tricks of the trade. Perhaps nobody in the state of Washington has eradicated more English Holly than Henry. After a long career as a doctor, Mustin retired in 2013 and began dedicating several days a week to bushwacking deep into the woods to destroy the plant he loathes. Henry has teamed up with DNR and while he is currently working primarily on Tiger Mountain he is the guy who removed the holly infestation on Little Si! Henry and Adam are really fun to spend time with and they both share their time and knowledge with kindness and generosity. Henry may join us at our first event on March 7!
Photo of Henry Mustin and Adam Kline, holly removal experts, courtesy of Anne Newcomb
Once English Holly is removed native plants return. With native plants come native insects and animals drawn by age-old connections between flora and fauna.
This is going to be an enormous but gratifying project. We will need your help! Please consider signing up for our restoration events on the IATC calendar.
References:
https://www.nwcb.wa.gov/pdfs/English-holly-Ilex-aquifolium-written-findings-2022.pd
https://kingcountyweeds.com/2021/12/23/not-so-jolly-holly/#holly-s-history