Invasive plant nemeses
Invasive plants are a part of garden life, but that doesn’t mean we can’t grumble about them. My invasive plant nemeses are the three that make my hair stand on end, my jaw clench, and my mind race with one thought: “KILL!” Of course it’s not the plant’s fault; it’s just in the wrong place!
But first, what defines an invasive plant? I often hear the term used incorrectly by gardeners so let’s get it straight before I tell you about my floricidal rampages. Simply put, an invasive plant species is one that:
Is not native to the given ecosystem
Causes harm to the native ecosystem by its presence
When it comes to plants, this often means that they spread rapidly by seeds (carried by birds). This also means that, when you hear someone refer to a plant that is native to your area as “invasive” they are incorrectly labeling that plant. Plenty of native plants are aggressive but, because they are native, it’s not possible for them to be considered invasive, which is an important distinction. For example, certain types of goldenrod can spread very quickly in a garden depending on the circumstances, but it’s native here in Wisconsin. You might call goldenrod aggressive in your garden, but you could not call it invasive. On the other hand, not all non-native species are inherently invasive if they don’t crowd out or harm other species in a given area.
It’s always a good idea to check on the status of non-native plants in your area. Even within the United States, some non-native plants can be considered invasive in some climates and not in others. This information is usually easily found online and your local extension service can be a big help.
With that out of the way, let me tell you about my favorite enemies.
Buckthorn
If you live in the upper Midwest, you’re probably familiar with this scourge, and you have probably had it in your yard. It’s a tall shrub that can grow up to 25 feet tall (more like a tree, if you ask me!). It produces small black berries in the fall, which birds eat and then poop out the seeds. A tale as old as time, really. There are lots of helpful buckthorn identification guides online, and once you learn to see it you’ll notice it everywhere. Once I learned to identify it, I realized with horror that it was positively choking out the evergreens in the back right corner of our backyard. Over the course of one satisfying weekend in fall 2022, I took it on. I bought some liquid brush killer, cut down every last buckthorn trunk, and used a paintbrush to dab the brush killer onto each fresh cut. Fall is an ideal time to do this as at that time sap is running down toward the roots of the plant, carrying the herbicide with it.
Here’s a Wisconsin DNR page about it and a USDA page about it.
Some pictures of pre- and post- buckthorn removal from the evergreen corner of the yard:
Garlic Mustard
Another classic! At least garlic mustard is edible so you can enjoy the fruits of your labor after you spend hours pulling it out of your yard in early spring. Garlic mustard is, like all invasives, a vigorous spreader and your neighbors will thank you for taking it out of your yard. It’s a cool-season grower, so it pops up especially in early spring and late fall. You can hand-pull it out, and it’s best to do so before it begins to flower (also, best tasting before it begins to flower). We have patches of it, large and small, that pop up in our yard every spring and I take it out as best I can. In fact, my first gardening act after we bought our house in March 2021 was to sit under the blue spruce tree in the front yard and pull garlic mustard that April. After a couple of years of pulling it out each spring, it no longer comes back in that particular spot. It starts out low to the ground in shade and semi-shade but can reach up to a couple of feet tall, with little white flowers, if allowed to mature.
A Nature Conservancy article about garlic mustard (including eating it!) and a Wisconsin DNR page about it.
My first garden project after buying our house: pulling garlic mustard.
Japanese Angelica Tree
This one was and remains a bit of a head-scratcher for me. During our second summer of home ownership, I watched in horror as an incredibly thorny, leafy, woody plant all but took over the perennial border in the back yard. It grew incredibly fast, taller than I am before I could blink. I couldn't identify it for a long time and, without being able to, I was reluctant to try and take it out. What if it was poisonous and I should take certain precautions before touching it? It looked to be out of a horror movie, with incredibly sharp spines covering every centimeter of the trunks and branches and big, monstrous, compound leaves reaching in all directions.
When I finally figured out what it was, I still wasn’t 100% sure. It looks almost identical to a native plant called Devil’s Walkingstick and unfortunately the best way to tell the difference is by the color and shape of the inflorescence, which appears in late summer. During the fall of 2022, I set about removing it by hand pulling. It spreads by underground rhizomes, so although I pulled out everything I could see, new plants continue to pop up from those rhizomes. Fortunately now I know to look for it and pull them (carefully, wearing thick leather gloves so as not to be stabbed!) as soon as I spot them.
This one continues to stump me as to its origins in my yard. As far as I can tell, it’s become a common invasive in Pennsylvania, Maryland, and Delaware, but not so much in Wisconsin. This is part of why it took me so long to identify it: it doesn’t appear on the lists of invasive species in my state. How did it come to my yard? I’ll likely never know, but I’ll also never forget about it as I’ll be pulling it and its squishy rhizomes out for the rest of time.
A National Park Service page about it and a Maryland Invasive Species Council article about it and its almost identical native cousin.
Also, you might find useful this New York Botanical Garden PDF booklet about invasive species and their similar-looking native counterparts.
