English Ivy is Pretty . . .
Pretty Invasive, that is!
(Invasives-Schminvasives, Part 3)
But it looks so classy climbing up a building
. . . as long as you commit to repeatedly climbing up and down a ladder every year to keep it pruned and in check, and you’re sure you have no cracks or weaknesses in your exterior’s surface, which this pretty, but invasive (or at least aggressive) vine will exploit. Oh, and the critters – as long as you’re okay with all the critters its dense foliage will attract like a brand-new apartment complex!
And the fact that, as is always the case with non-native plants that are classified as invasive, it can escape your shade garden or border planting to wreak (more) havoc in natural settings, or on your neighbor’s property.
How is it invasive?
English ivy (Hedera helix) is a widely popular plant in American gardens for good reason: it’s attractive. It grows well (and quickly) in a variety of conditions (especially shade). It can act as a uniform, dense ground cover, but can also climb up vertical surfaces to act as a screen. What’s not to love?
Unfortunately, the same characteristics that make it attractive to many as a landscape plant have caused it to be added to the invasive species lists of many states (at least 18 that I can find, including the entire west coast and most of the east from parts of southern New England through the mid-Atlantic and the southeast, along with parts of the Midwest and mid-South). In states where it isn’t officially listed as invasive, it is often quite aggressive and retains the potential to become invasive, thanks to its ability to spread by runners and seed, and the fact that the leaves are poisonous and therefore aren’t able to be controlled by the browsing of deer or other vertebrates. New plants can also sprout fairly easily from fragments of stem that come into contact with soil, for example, when it’s being cleared if all parts of the plant aren’t properly removed and killed.
English ivy causes damage in a few ways, ecological and otherwise:
1) It has very dense leaf cover, which, when growing on a forest floor, will choke out most other plant life, including beneficial natives. (So, lovers of lady slippers, ferns, and other delicate woodland beauties beware)! This dense cover can also cause moisture problems on structures;
2) It climbs anything and everything in its path. When left unchecked, its vines grow thick and woody, and they attach themselves to trees and buildings via root-like structures that add insult to injury by exuding a gluey substance to help them adhere more firmly. For trees, this can spell trouble over the long term: between the weight of the vines and the density of the foliage – which deprives a tree of its ability to photosynthesize - it weakens, and can eventually kill its hosts (not unlike our foe, Asiatic bittersweet, which I covered previously). It can also be a significant danger if growing on trees near houses or other structures, as weakened branches or entire trees can fall;
3) On buildings, while there’s a bit of controversy as to whether it’s damaging to otherwise sound structures, if you have even a hint of weakness: cracks in mortar or concrete, damaged or rotting wood siding or trim, really any small opening of any kind, English ivy (via its tendrils and “glue”) will find its way in, expanding fissures as it grows. It invites habitation by all manner of creature, from insects to birds to reptiles, and its propensity to hold moisture can cause wood to rot;
4) In areas prone to erosion, while you might think a thick carpet of ivy would be a great solution, think again: its roots are relatively shallow, and water can easily work its way under the ivy and into the soil, causing the full mat of ivy and the soil in which it’s growing to slide downhill.
Identification
While I suspect that, thanks to its ubiquitousness, most of us recognize Hedera helix when we see it, it never hurts to be sure!
One thing to be aware of is that it has both juvenile and mature forms, and the leaves of each look quite different. The juvenile plant grows along the ground. It almost always has light-colored veins that contrast with the dark green, waxy leaf, which typically has 3 – 5 lobes. New growth is lighter in color and lacks the waxiness that develops as the leaves mature.
Juvenile English ivy (photo courtesy of the author)
Once English ivy starts growing vertically, it can mature, and the leaf form will go from lobed to rounded. The leaves tend to be larger than they are in the juvenile form. In the fall, it forms very small green flowers in umbels (they come off a stem in an array that looks a little umbrella-like) and the berries mature over the winter, becoming dark purplish-blue. Even though the berries, like the foliage, are toxic, native birds still eat them. The toxicity doesn’t kill most birds, but it does cause diarrhea, which helps to ensure seed dispersal. (Sneaky, eh?!)
Mature English ivy with fruit clusters (photo courtesy of Lisa Gould)
Both the juvenile and mature forms have leaves that alternate along the stem (versus “opposite” growth, where two leaves grow from the main stem directly across from one another), and the leaves and stems of both forms can cause an allergic skin reaction in humans, so wear gloves if you’re going to be working with it.
Eradication
Many people battling an English ivy invasion find that manual removal methods are more effective than chemical ones. This is thanks to the waxy coating on the leaves, which tends to thwart penetration of liquid herbicides. Therefore I’m going to focus on manual methods of removal first, and I’ll come back to the chemical at the end.
Thankfully, because the roots are relatively shallow, English ivy pulls fairly easily, though it can be more difficult when the affected area is particularly dense.
Method 1: Cut and pull.
a) This is focused on juvenile ivy growing in dense patches along the ground. You’ll need a wide, sharp blade, like an edger or a flat-head shovel and sharp clippers or pruners, plus, of course gloves and probably long sleeves and pants to protect your skin from the allergen in the leaves and stems. You’ll also need either heavy-gauge black plastic garbage or contractor bags, or the space to allow what you’ll dig up to dry out and die (a sunny spot on the driveway works well). This technique also works best when the ground is wet – it doesn’t have to be soaking, but if you can get out after a pretty good rain, the whole thing is easier.
b) Using your sharp shovel or edging tool, cut two parallel lines about 2 – 4’ apart down into the ground and through the roots at the edge of a section of growth. Starting at the beginning of the section, pull the ivy up between the cuts, and start rolling it up like a dirty old rug. You may need to dig a little with your hands or the shovel, or cut across it with your clippers close to the ground to get under the roots to pull them up, but it shouldn’t be too difficult thanks to those shallow roots.
c) If you find the roots are more difficult to pull and the ground is dry, try soaking it with your hose or sprinkler for long enough to soak the soil a couple of inches down, which should make removal easier. If you can’t soak it, just do the best you can. You should still be able to make a good dent, and pulling regrowth gets easier the longer you keep at it.
d) Work in sections and don’t be afraid to spread the job out over time. The ground should be mostly bare where you pull it up, and it will be pretty easy to spot any regrowth or to use your favorite plant ID app to identify anything new that pops up so you can decide what to let grow and what to pull. (The density of the ivy can hide and suppress seed banks of many plants that are just lying dormant in the soil. Once they’re exposed to better light and moisture, they can break dormancy and start growing).
e) Dry out or kill what you pull up before sending it to the dump or throwing it in your compost or brush pile. If you don’t have the space to dry it out, bag it in your heavy gauge black plastic bags and solarize them (put them someplace sunny for a few weeks).
Method 2: Mow, mow, mow.
As with most plants, ivy grows and gets stronger as it photosynthesizes. If your ivy is in a place where you can mow it, have at it! Set the mower deck as low as possible, and mow regularly to inhibit growth and thus, the ability of the leaves to continue feeding the roots.
Method 3: Sheet mulch/smother.
a) Cover the area - preferably with plywood – but you can also use cardboard or a thick layer of newspaper topped with a layer of mulch at least another 4” thick. This method will take a long time and the ivy roots will naturally “reach” for areas where they can put up new growth unimpeded beyond the edges of the sheet mulch or plywood, but it’s a little easier to monitor the edges and pull from there. This will eventually deplete the energy stores of the roots by eliminating (what?) photosynthesis. You’ll likely have better results if you cut it back first, by mowing or weed-whacking it, and sheet mulching over the cut sections.
Method 4: More eco-friendly chemical warfare.
This can be accomplished with a vinegar solution, but will need repeated application, may not fully kill the ivy, and can be harmful to desirable plants nearby. The vinegar will break down in the soil fairly quickly, but the salt can build up over repeated applications if there isn’t enough rain/watering to dilute it and it can harm the soil and microorganisms, so it’s best to use this mixture judiciously.
a) Ingredients: 1 gallon white vinegar; ¼ cup dish soap; 2 cups Epsom salts or table salt. (The dish soap will act as a surfactant and help the vinegar & salt to penetrate the waxy surface of the ivy leaves). I use a pump/pressure sprayer I bought on Amazon but you can put the mixture into a smaller, regular spray bottle, too. (Note: the recipes for this solution vary in the amount of salt they call for, with some suggesting as little as one tablespoon of salt per gallon of vinegar. You can always experiment – at least the ingredients are cheap)!
b) If your spray container is big enough to hold all the ingredients you can mix up your solution right in the sprayer, but otherwise, use a bucket or, better yet, a large enough container with a lid to keep the mixture so you can just refill your spray bottle when you need to. Pour the salt in first, followed by the vinegar, then stir or shake until the salt dissolves. Add the dish soap and stir or shake to combine. Pour into your sprayer and you’re ready to go.
c) Choose a dry, sunny day with little or no wind, and spray in the morning if possible, avoiding any other nearby plants. Also try to pick a day when no rain is forecast for at least another 2 – 3 days. Try to soak all the leaves evenly. You should see the ivy start to wilt and turn brown within a couple of days. If it rains too soon after application it can dilute the treatment and make it less effective.
d) Once the patch has died back, pull up the dried plant and roots, and/or monitor for new growth. Mow, clip, or re-spray whenever growth appears to keep the new growth from feeding the roots.
Method 5: Glyphosate.
Works best on new growth only, as newer leaves lack the waxy coating that prevents the chemical from penetrating the leaves. Application will be most effective if you cut/weed whack, or mow the area first, wait for new growth, then apply the glyphosate, or spray in the spring, when new growth is naturally occurring. Beware, however, that it will take repeated applications to fully kill the ivy.
Some people recommend triclopyr rather than glyphosate, but I’m a bit more leery of triclopyr because it can transfer through the roots of the target plant to the roots of other nearby plants or trees, where glyphosate won’t do that.
If the ivy is growing up trees:
Using a flat-head screwdriver and working around the tree at chest height, carefully pry each vine from the tree in a spot big enough to get your clippers around it. (If the vine is especially large/thick, you’ll need a hacksaw or something beefier than clippers to cut through it)! Cut each vine, and gently peel the bottom section off the tree (if you find that the vine isn’t coming off easily when you peel from the top down, or is breaking off, try pulling the vine from the bottom up instead). Some sources also recommend cutting each vine at the bottom of the tree and removing the cut section. Don’t attempt to pull off the vines that are still higher up the tree/in the canopy. It can damage the tree or pull weakened branches down on top of you.
Next, remove the ivy that’s growing around the base of the tree to at least a six-foot radius. As above, this is best accomplished by pulling when the ground is wet.
In summary
Hedera helix can be a pain and time-consuming to eradicate, but it’s not as bad as some other invasives. Starving the roots by shortcutting photosynthesis is one way to do it if it’s somewhere that makes pulling it difficult or impossible. Otherwise, pulling when the ground is wet is most effective. It will take time, some energy, and consistent monitoring for regrowth to fully eliminate it and keep it away, but in most places, it doesn’t grow as quickly as some other invasives, which helps to keep it somewhat more manageable. Both chemical and non-chemical spray treatments work best on new growth, and the best overall approach is often a combination of several methods. The longer you leave it alone, though, the more of a challenge English ivy becomes to eradicate, and the more ecological damage it does.
The best way to help bring it under control on a large scale is to STOP BUYING AND PLANTING IT!
Good luck, and let me know if you have any questions!!
