English Ivy – January 2017 Weed of the Month

During the winter months in the Pacific Northwest, English ivy stands out even more than usual. Although some people enjoy the evergreen look of it on fences and tree trunks, English ivy is also at its worst in the winter here.

Photo of English ivy growing in a Seattle neighborhood
English ivy seen in a West Seattle neighborhood on a cold day in January. Photo by Sasha Shaw.

Heavy vines covering the upper canopy and limbs of a tree become even more of a burden when they are weighed down with wet snow and ice. During wind storms, ivy blankets can turn into giant sails and create hazard trees that can topple down on houses and people. Around our houses, English ivy becomes a refuge for rats and other critters that are unwelcome visitors in our homes.

Photo of English ivy growing on trees on a roadside.
English ivy covering trees along a road in King County in the winter.

Fortunately, English ivy is also relatively simple to remove. Granted, it can be physically difficult to uproot its woody vines, especially when it’s old growth ivy that’s been growing for decades. But who doesn’t need a little extra outdoor exercise this time of year?

Pick a relatively pleasant day, dress warmly, grab your work gloves and some tools to pry the vines off tree trunks, and head out to your ivy patch. The vines that are growing on vertical surfaces like trees and fences can be cut around chest height and then pulled off the lower surface. It can be hard at first to pry off the vines, but once you get some of it free, the rest should pull off fairly easily.

The same is true of ivy growing along the ground. Grab hold of a vine and often you can pull up huge lengths of it without too much trouble. You can have contests to see who can remove the longest vines or the thickest stems!  Even a small group can make quick work of a  large patch of ivy.

Be careful though. English ivy can cause serious skin reactions for some people. Make sure to wear gloves if you don’t know how you will react. In addition, people can be sensitive to breathing in dust from the ivy, so stop working if you notice any problems.

Also, before you remove ivy from a tree, carefully inspect the tree to make sure it isn’t dead and at risk of falling over on you. Sometimes ivy’s thick vines can temporarily hold up trees that have died underneath its growth. If the tree could put people or buildings at risk, get a professional tree expert to take a look first. If there’s no risk of injuring anything or anyone, you can also just give the tree a hard push and see if it topples all on its own. Just make sure you aren’t in its path!

Photo of a tree with old English ivy vines that have been cut and pulled off the lower trunk.
Tree with old English ivy vines that have been cut and pulled off the lower trunk.

In spite of the problems it causes here, I will admit that English ivy (Hedera helix) is a rather remarkable species, or group of species according to some botanists. Individual ivy plants can live over 100 years, stems can grow over a foot thick, and older vines can grow 90 feet long. In its native habitat in western and northern Europe, English ivy is a very useful plant, offering abundant fall nectar for numerous insects, and winter and spring berries for many birds. When ivy grows on houses, it can provide insulation in winter and summer, and some people value it for adding green to bare walls and tree trunks.

Photo of English ivy growing on a house with a cat in the window.
English ivy growing on a house surrounding a window with a cat enjoying the view.

Unlike in our area, English ivy grows well with other plants in its native range and doesn’t dominate the landscape or harm trees to quite the same extent. However, even in Europe, English ivy is a concern when it overwhelms a valued tree or grows too vigorously on walls and houses.

English ivy has many varieties and subspecies, ranging from small, star-shaped leaves to large, almost unlobed leaves, but they all look fairly similar and grow in more or less the same way. The general look of the plant is a spreading, branching, long-vined ground cover.

Ivy can grow along the ground, on walls, and up trees. It climbs by producing a glue-like substance from small, root-like structures that allows it to stick to tree bark and other surfaces. The climbing vines continue to grow up and out, eventually covering even very tall trees. The growth of English ivy on trees is really quite dramatic. Ivy can climb up to 30 feet a year and can top a 300 foot conifer.

Photo of a tall conifer covered in English ivy
Tall conifer with English ivy covering its trunk.

When ivy matures and is exposed to full sun, it forms short, upright, side branches that have unlobed, shiny leaves and umbrella-shaped clusters of small green flowers, followed by round, black berries. These mature stems are often high in the tree canopy, making it easier for birds to access the berries and disperse the seeds, but flowering stems can also be seen on fences or sunny hillsides. This mature form of ivy has even been marketed as its own variety and called “flowering ivy”.

The reason we have so much English ivy in the Pacific Northwest is that it grows really well here and it has been highly popular as an ornamental vine and ground cover for well over a century. When a plant is introduced so many times, it greatly increases the chances of it becoming a problem, especially if it is also well-suited the climate and able to spread easily on its own. Also, unlike in England and elsewhere in Europe, ivy seems to have no checks and balances on its growth in this part of the world. Left alone, English ivy often grows so densely that it creates an “ivy desert” that excludes other forest plants and inhibits the growth of tree seedlings as well as speeding up the demise of the mature trees.

Photo of English ivy in a forest surrounding a native trillium plant.
English ivy in a forest surrounding a native trillium plant.

If you are fortunate not to have an ivy problem of your own, consider helping a neighbor or a local park. Contact King County Parks or your local Parks Department for information on volunteer events, or visit the events page of organizations such as EarthCorps, Mountains to Sound Greenway, Forterra, or the Nature Consortium, to name just a few. There is plenty of ivy out there that needs pulling and it’s a great time of year to do it!

English ivy growing around a stop sign in Seattle, Washington.
English ivy growing around a stop sign in Seattle, Washington.

English ivy is Class C noxious in Washington and the King County Noxious Weed Control Board recommends that people remove it where possible and avoid planting it. King County and many local cities and other agencies are beginning to reverse the decades of ivy spread and to restore forests that have been invaded with the help of many dedicated volunteers. There is still much work to be done, but working together we can make a difference. For more information about English ivy or other noxious weeds, please visit our webpage or contact us.