A Silent Green Threat to Thousands of Local Trees

by Michael Feerer

English Ivy and other tree-climbing invasives threaten to prematurely kill thousands of trees within Whatcom County. This is slowly and silently degrading our local parks, forests, and neighborhoods. It’s reducing our region’s climate resilience and biodiversity while robbing us of the many other benefits that trees provide. In this article, you’ll learn how Whatcom Million Trees Project is working at an unprecedented level locally to change that sad fact, and how you can easily help.

With so many challenging environmental issues in Whatcom County these days, one can easily feel overwhelmed and discouraged. However, good work is being accomplished by local nonprofits and individuals to make progress on many issues. Some of you may even be personally involved in such efforts. Whatcom Watch does a great job of covering this arena. 

Mature conifers, big-leaf maples, and a wide array of smaller native trees form a fundamental part of the urban and rural character of wonderful Whatcom County. So it’s no surprise that an issue often at the forefront of individuals’ minds is the pervasive loss of our much-needed mature trees.

Loss That’s Below the Radar
People notice human-caused tree losses from new development, logging, arborists, etc., especially when it suddenly occurs near their home or is otherwise glaringly in view.

What people don’t notice is the slow, insidious loss of mature trees from another cause: invasive vines that aggressively climb trees. Being nonnative, this is also essentially a human-caused condition.

This article focuses on one particular tree-climber: English ivy. Although Atlantic/Boston ivy is significantly in the Pacific Northwest ivy mix now, and four of 60-plus English ivy cultivars are the most aggressive, for simplicity I’ll call it all “English ivy.” Other tree-climbing invasives with lesser impact are reviewed at the end of this article.

English ivy is not native to the Pacific Northwest, but thrives in our temperate region — especially along the edges of parks, trails, clearings or other open spaces, and roads.

The vines can grow up to six feet per year and can approach 100 feet in length. They opportunistically climb upward, seeking more sun in any way they can. That includes climbing any tree in its path.

Their collective destruction is enormous. On the ground, English ivy dominates and smothers all other understory plants. But up high is where even more dramatic loss occurs. Most residents in Whatcom County don’t realize a stunning fact: Thousands of mature healthy trees locally are threatened by English ivy. Virtually all of those trees will die prematurely in a handful of years.

For decades, English ivy has been sold and promoted by nurseries and landscapers as a quick, easy ornamental groundcover solution. Why? Because it’s so aggressive!

And now it has escaped our gardens and has no limits. Robins and other birds snack on the ivy’s seed-filled small black berries, then spread the seeds in droppings, often miles away. That’s how English ivy ends up in our parks and forests, although sometimes homes adjacent to such greenspaces can also be a source. (Several Bellingham urban parks have this problem.)

Community-wide, English ivy is slowly and silently degrading our local parks, forests, and neighborhoods. It’s reducing our region’s climate resilience and biodiversity while robbing us of the many other benefits that trees provide such as filtered air, flood reduction, cooling shade, energy savings, visual/noise buffering, stress relief, improved health, natural beauty, and more.

Yet the ivy problem sits below the radar of most residents and policymakers. Local parks and public works departments tend to be aware of the problem but typically lack funding to do much about it. It would be expensive to pay for removal, and those departments have too many other balls to juggle.

Bottom-line: English ivy is a silent, slow tree-killer that’s spreading in plain sight. The problem in Whatcom County must be addressed before it grows far worse, slowly robbing us of thousands of mature trees.

Tree-Killing Progression
The typical English ivy tree-killing progression goes like this:

Step 1: The vines spread on the ground toward a tree and then start to climb the trunk, seeking more sun. At this point, the vines only slightly weaken the tree by wrapping shallow roots around the tree’s base and competing for moisture and soil nutrients.

Step 2: More and more ivy vines climb the trunk, attaching themselves more securely to the bark as the vines thicken. The tree remains only slightly weakened.

Step 3: The ivy reaches the tree’s canopy within a few or more years, depending on sun exposure and other variables. Now the tree’s leaves begin to experience competition for sun and moisture, weakening the tree considerably.

Step 4: The weakened tree is burdened with a dense, top-heavy upper canopy of leaves and ivy. The extra weight can easily approach one ton on a large tree. The next strong windstorm that comes through (which are more common now due to climate change) will likely snap off the top of the tree, leaving a dead snag.

Once the tree is a dead snag, it begins to emit rather than capture carbon from the atmosphere and it will stop providing most of its other benefits. 

WMTP’s Ivy Removal Progress
The good news is individually and together we can significantly reduce the English ivy infestation in our community. Whatcom Million Trees Project is leading this effort. Our long-term goal is to remove English ivy from the vast majority of trees within Whatcom County.

Our three-year goal is to save at least 80 percent of the ivy-threatened trees in Bellingham, outlying cities, and parks throughout Whatcom County.

To date, WMTP volunteers and our Americorps interns have cleared — and thus protected — more than 1,400 trees from English ivy. It’s a very direct, satisfying, positive climate action that everyone locally can support or participate in.

 

But clearing ivy from trees is only one facet of our strategic, multipronged effort. Our English ivy removal efforts include:

• English Ivy Mapping

• Ivy Removal Work Parties

• English Ivy Removal Guides

• Community Education

• Local Nursery Advocacy

• Statewide Nursery No-Sell List

Each facet is summarized below.

English Ivy Mapping
Mapping is an essential first step. Once you know what English ivy looks like and realize the threat it brings to trees, you begin to have what we call ivy eyes. You start to see it everywhere!

WMTP volunteers with ivy eyes have been walking parks, Greenways, roadways and rights-of-ways to locate and count the largest ivy clusters plus various smaller infestations. 

Altogether, to date we’ve identified over 2,700 mature trees that are threatened by ivy, as you can see in our handy interactive Ivy Removal Progress Map found on our website.

Links for all resources mentioned in this article are on our ivy page at https://whatcommilliontrees.org/tree-projects/tree-protection/english-ivy/

In the interactive map on our ivy webpage (see note above), you can zoom into any neighborhood or street location. Larger dots indicate greater quantities of ivy-affected trees. Clicking on a dot pulls up our data for that location. The percentage of ivy removed is shown by the circle’s color.

Our mapping helps us to strategically plan work parties in the most concentrated areas first and to track our progress. It also informs us where to periodically re-check trees in future years to ensure ivy has not returned onto the trunks.

So far, most of the mapped trees are in Bellingham. Now we are filling in data gaps and working outward. County-based WMTP volunteers are starting to gaze with ivy eyes, too. Last but not least, staff from Whatcom County Parks and their equivalents in Ferndale, Lynden, and Blaine are helping to identify ivy-affected tree locations in their parks for us. We suspect we’ll eventually discover at least a few thousand more affected trees within Whatcom County. Yikes!

Know of ivy-burdened trees that we haven’t mapped yet — on public or private land? Please email us at info@whatcommilliontrees.org Be sure to mention the approximate quantity of trees affected and the location (street address or map coordinates/pin).

Ivy Removal Work Parties
Since mid-2022 (except during late fall-winter, our tree planting season) we’ve held two or more WMTP volunteer work parties per month to remove English ivy from mature trees. Typically 15-25 volunteers armed with hand pruners and loppers have fun enthusiastically working together in such a climate-positive way.

The relatively easy work typically creates a strong feeling of satisfaction in each volunteer. Anyone 8 years or older can participate. We’ve had many seniors involved, too. No tree climbing or special skills are needed. As a bonus, you’ll learn hands-on from us how to clear ivy safely and easily from your yard!

Want to join one of our fun ivy removal events? Go to https://whatcommilliontrees.org/work-party-volunteering/

or click the Ways to Help > Work Parties menu of our website.

English Ivy Removal Guides
Our proven English ivy removal technique is useful not only for WMTP work parties but for individuals at home. 

For complete step-by-step details of how to safely and easily remove English ivy, see our WMTP English Ivy Removal Steps PDF on the ivy page of our website.

In a nutshell, we carefully remove ivy from each tree trunk ONLY from shoulder height on down. We fondly call that point the Circle of Survival for the tree. In park/forest settings, we work at that height for safety reasons and to easily monitor from afar which trees we’ve cleared. 

At home, you can create your Circle of Survival at waist height or lower if you prefer since monitoring from afar usually isn’t needed.

No special tools are needed. Garden hand pruners usually are up to the task. Sometimes a small handsaw or lopper can be handy to carefully remove thicker roots of older ivy strands.

Regardless of the Circle of Survival height, all higher strands will die and fall off over several months. There’s no need to yank off ivy strands from higher. All you need to do is to be patient with the die-off process. The speed depends on weather, sun exposure, ivy maturity, and other factors. But rest assured that your good work will eventually completely unburden the tree.

After the lower trunk is cleared, on the ground we clear a 6-foot diameter around the tree’s base. This typically gives the tree at least a few years before English ivy may climb the tree again.

Why do we not remove all ivy that’s on the ground? With so much infestation, we view ivy removal as an ongoing process. Each removal wave by us or others will push it even further from tree trunks, but our top priority in the first wave is to get it off the trunk and away from the base to rapidly save as many trees as possible now.

The last removal step is to chop the removed cuttings to forearm length and then “air-compost” them on-site. That means spreading the cuttings away from the trees on top of other ground ivy and bushes that will keep the cuttings off the ground. Or sometimes we create ivy mounds in the middle of other ground ivy. Only if necessary, we bag and remove it for industrial composting at Green Earth Technology in Lynden.

At home, you can air compost like above if you have sufficient landscape area and don’t mind the temporary visual clutter among your plants. If not, do NOT put ivy in your compost bin! Most home composters will not fully kill it. Instead, put it in your yard waste pickup bin (if available). Or, place your ivy cuttings on a tarp in the sun for a few weeks or longer — until the cuttings turn completely brown — as an effective alternative.

Community Education
As mentioned earlier, most residents don’t realize that English ivy will prematurely kill virtually every tree it climbs. To improve awareness, WMTP has been giving ivy-removal presentations in local libraries, neighborhood associations, clubs, and other small-scale venues. And writing articles such as this one.

Want us to speak to your group? Please contact us at info@whatcommilliontrees.org — we’ll be happy to!

We also have a half-page English Ivy Flyer at our website (and shown at the end of this article) which anyone can print and give to a neighbor (or slip into a door frame) who has threatened trees. It briefly alerts them to the ivy problem and provides WMTP’s resources for easy, safe removal. Most homeowners can remove it themselves or with minimal guidance from us.

Local Nursery Advocacy
Believe it or not, several local nurseries (retail and wholesale) still sell English ivy! This is the root cause of the problem. We are trying to persuade them to stop selling it and to instead suggest to customers native alternatives for ground cover. Note that such a switch will create no revenue loss for the nursery — in fact, a nursery might gain revenue because more containers of less aggressive alternative ground cover may be purchased!

As you can see in the chart on the next page, Garden Spot Nursery in Bellingham is leading the way in this switch. We hope others will follow. We are also approaching wholesale nurseries in our region that supply the big box stores and retail nurseries in our area.

As an incentive, we offer to any nursery who willingly switches lots of favorable promotion in our e-newsletter, social media, and at work parties. We prefer this “carrot” approach because WMTP’s primary role is to build positive partnerships of people working together to improve local climate resiliency and biodiversity.

Unfortunately, as shown in the chart on the next page, some local nurseries after hearing from us still have chosen to sell English ivy. If any are your favorite nurseries, you can help to persuade them the next time you visit. Kindly ask the staff to no longer sell English ivy! The more they hear from customers like you, the more they may reconsider their decision.

Statewide Nursery No-Sell List
What can we do about the sticklers — the nurseries that refuse our carrot to switch? We wield a last-resort Big Stick.

The Washington State Department of Agriculture (WSDA) has a Prohibited Plants and Seeds List. The WSDA list prohibits nurseries and other stores in Washington from selling harmful plant species.

Unfortunately, English ivy and Atlantic/Boston ivy are currently not on that list. We therefore have begun the long process to change that. (Note: This list is different than the state’s Noxious Weed List, which does list English ivy but has no regulatory power.)

Annually, an obscure committee within the WSDA considers changes to the prohibited list. At that time, we will present petition signatures and testify, using economic and climate impact arguments to advocate for change.

Here’s how you can easily help: Please sign our ivy petition online. The petition urges WSDA to add four specific ivy cultivars (the most aggressive ones) to their Prohibited Plants and Seeds List. You do not need to be a registered voter or over 18 to sign.

On the petition form is a Comment field. Consider writing a few heartfelt sentences in your own words why you want English ivy sales to be prohibited. These comments will be presented to WSDA too and can be quite potent.

Last but not least, be sure to share the petition link with your tree-loving friends and family so they can sign it, too. We hope to have thousands of petition signatures by time we present to the WSDA committee early next year.

Other Tree Climbing Invasives
Besides English ivy, a few other climbing invasive vines in our region also suffocate trees, leading to dead snags. The top three are morning glory, clematis, and old man’s beard. However, they collectively affect far fewer trees here than the thousands impacted by English ivy. When we encounter other climbing invasives during our English ivy removal work, we clear the trees of all.

What about one of the most common and visible invasive plants in our coastal region — Himalayan blackberry? Ugh! It has taken over so much land throughout our county. Probably your yard or neighbor’s yard has some. Mine still does! 

It’s indeed a high-priority invasive plant that deserves far more removal attention. But, its impact on trees is different than invasive climbers. Himalayan blackberry doesn’t kill trees. Instead, it prevents small tree seedlings from naturally regenerating. This cumulatively also has big implications for our local urban and rural forests, but that’s a story for another day.

Online Resources About Invasives
Whatcom County’s Noxious Weed Program has some excellent online Fact Sheets where you can learn more about all tree-climbing invasives. (For links, see our ivy page at our website.) They are also available by phone at (360) 778-6234 and staff there are happy to offer helpful advice about specific invasive situations you may encounter. 

You’ll see that their Fact Sheets tend to include chemical herbicides, such as glyphosate-based products like Roundup®, among suggested removal strategies. Whatcom Million Trees Project doesn’t recommend that approach and absolutely will not use chemical herbicides in any of our projects. We refuse to subject our volunteers, staff, and living beings of all sizes and shapes to poisons that we believe in the big-picture will be counterproductive to the healthy restoration of our local lands and waters.

In Conclusion
There’s no need to feel powerless to stop the immense loss of mature trees we are experiencing in Whatcom County. There’s no need to wait for agencies to gain the resolve and funding needed to finally act. Individually and collectively, we all can systematically turn the tide of English ivy and other tree-climbing invasives ourselves, thereby improving the health and climate resiliency of our entire region. It’s very rewarding but relatively easy work that truly makes an immediate and significant difference.

Solving the ivy problem is only one facet of the wide array of Whatcom Million Trees Project initiatives to protect our local trees. If you haven’t seen the full range of our many tree protection efforts, visit our website today. Even if you’ve browsed our website previously, take a fresh look since we recently updated our pages to show much more of our work.

Tree protection keeps us plenty busy because there is so much that urgently needs to occur locally to save our trees. It’s one reason why we have been embraced so quickly in our brief two-plus years of existence as a 501(c)(3) nonprofit. We are grateful for the community’s strong support of WMTP and how so many have taken our multifaceted mission to heart.

Want to join any of our cool tree-saving planning and advocacy efforts? Or have a question about this article? Please get in touch at info@whatcommilliontrees.org

Thanks for reading and start using your ivy eyes today! 

WMTP Resources

WMTP Tree Protection Initiatives
https://whatcommilliontrees.org/tree-projects/tree-protection/ 

or click the Projects > ALL Protection Projects menu of our website.

WMTP’s English Ivy Removal Main Page
https://whatcommilliontrees.org/tree-projects/tree-protection/english-ivy/

Note: All resource links mentioned in this article are available here.

WMTP’s Statewide Ivy Petition

https://actionnetwork.org/petitions/stop-selling-english-ivy-in-washington/ 

or click the Ways to Help > Sign a Petition menu of our website.  

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