Think Twice Before Planting More Holly in the Northwest

Area residents thinking about adding some form of Holly to your domestic garden display this year should consider it very carefully.

English Holly is an attractive plant at first introduction, but it wears away it welcome over time.

While the several types of Holly that are in the local area are not listed as an invasive species, it creates headaches for homeowners and heartaches for forest managers watching over the northwest’s’ most pristine forests.

It should be noted the English Holly and several other related species are not considered noxious weeds in Washington State. Most counties west of the Cascades, however, recommend their control and discourage planting.

Holly has more than a few positive attributes. Many people love the beautiful berries and the fact that it is an evergreen that lends color even during the drab winter grayness.

The berries of the European Holly are very attractive, but birds take them to other locations where they spread the plant from its intended domestic habitat.

It is those berries though that leads to a much wider problem. Birds eat the fruit and then completely process it in its natural habitat. (Translation...the bird poops it from the limb of a tree after acids make the seed viable). Holly is extremely adaptable. It can grow slowly in the darkness of a thick reproduction forest or at the base of a 400 year old cedar deep in a wilderness area.

Holly grows will in direct sunlight, but can also survive in the darkness of an unthinned reproduction forest like this example.

The latter is a problem for managers at places like Mt. Rainier and Olympic National Parks. Holly has been found in some of the most remote forests in Washington State.
The spiky, waxy leaves protect the tree from any natural predators so the it is left unfettered to grow where it takes root.

Residents that have Holly in their yard gain a fuming disdain for the tree over time as they try to manage it. Clipping one limb leads to the growth of many more in the same location. What should be a stately tree of holiday lore becomes an impenetrable bush of spiny leaves. The holiday romance of holly eventually disappears.

These residents have attempted to trim the base of their holly tree, only to find out that it sprouts back exponentially.

Removing Holly is a seemingly insurmountable task. Cutting the tree down will result in sprouts around the base. Pulling a small tree in moist soil may work eventually, but roots and debris left in or on the ground will surly sprout to form. Control may be achieved through an annual visit to pull the remaining parts of the plant. A larger tree will need the use of a pesticide after cutting. Applying herbicide freshly cut stump or a frilling method is most effective. Foliar herbicide treatment is not very effective due to the thick, waxy leaves. If you want to remove your holly trees with an herbicide, contact your local noxious weed control board for more information on the best methods.

We have learned from our mistakes and now its time to stop making them. While Holly has its own beauties and folklore, it has worn out its welcome here in the northwest. Gardeners should look for more environmentally responsible alternatives before adding more holly to our neighborhoods and yards. This is a tree that knows no boundaries and humans inflict little damage to the spread of this increasingly noxious plant.

Photos courtesty of GAP Photo

The Spread of Holly Needs to be Checked

The bright red berries and pointed leaves are synonymous with peace and love of the holidays, but the rest of the year, Holly has become an invasive pest. In some areas of the Northwest U.S. and Western Canada, it is a crop much like our local Noble Fir but Holly is not native to the region and like many invasive species enjoys the ingredients it needs for success as well anonymity from natural predators.

Holly is quickly becoming an invader of Northwest Forests such as this small population in the Old Growth Forest at Lewis & Clark State Park.

In my work with invasive species, I hear many home and property owners complain about the plant as they tried to remove it from their yards. Like many invasive species, it reproduces in more than one way. Seeds are dispersed by birds which accounts for small populations well away from the parent plant. The trees also spread by “suckering” and “layering“. Suckering is the reproduction of a plant by shoots that arise from an existing root system. Layering is when the plant grows roots where stems touch the ground. Take a look through any of our local forests or reproduction lands and you will find small populations of Holly growing in areas devoid of solar radiation or in full sunlight.

While it is not listed on the Washington State list of noxious weeds, many other states and provinces are waging formal battles with the plant. English holly has become a serious pest in state and national parks like Olympic. Urban parks and arboretums in Portland, Seattle and Vancouver B.C. all have ongoing programs to eliminate the plants. More locally, The Friends of Seminary Hill in Centralia are slowly confronting the invaders along with Ivy in the Seminary Hill Natural Area.

On a recent hike, I also noticed a small population in the old growth loop at Lewis and Clark State Park near Toledo.

Holly is effectively controlled is by removing the entire tree and the entire root system, and then physically removing the tree and its branches out of the woods. A holly branch, if left on the ground, will grow roots and continue to thrive. Lopping off or cutting down Holly trees does nothing to the root system, and the plant easily sprouts new shoots and continues to grow.

I would employ the knowledge of a licensed professional or the local noxious weed control board and apply pesticide to the stump of a freshly cut holly bush or tree.

Holly has its uses, but like most invasive species, its presence is having unintended consequences on the natural system of our area. It is crowding out native plants and in some cases, physically impairs our movement in our own yards with its stiff, protruding leaves. Care has to be taken as even the best of intentions can make this plant more aggressive and difficult to treat.