Backyard invasives to know
Anne Gageby
Strawberry Hill Nature Preserve
(4/2025) Spring is officially here, and buds are making their debut. This is a great time to become familiar with some of our area’s biggest problematic invasive plants – Japanese barberry, stiltgrass, mile-a-minute, garlic mustard, and many more. You may spot some or all of these plants by roadways, along walking paths, or even in your own backyard. Most look innocent, if not sort of lovely as they grow. After all, greenery of all kinds makes a forest or field appear healthy and thriving. But non-native invasive plants can quickly take over an area, pushing out native species that our local wildlife depend on. This can leave wildlife vulnerable in a variety of ways that might not be readily apparent. It can also have a serious negative impact on local flora.
For example, Japanese stiltgrass displaces native herbaceous and woody plants by crowding them out but it also leaves a more nefarious impact: it changes the soil’s pH by making it more basic. Many of our native plants and shrubs need a more acidic environment to thrive. Our state flower, the mountain laurel, is one such shrub. Wood anemone and wild ginger, two lovely groundcover plants that attract early pollinators and butterflies, need acidic soil to grow. Even hardy spicebush, which can survive in a variety of soils, does best when the soil is acidic.
There is an upside to dealing with Japanese stiltgrass, however. It’s easy to root out by hand. The roots are shallow and weak so hand pulling takes little effort. It’s possible to get ahead of it if the infestation area is small. However, it will likely take time to fully eradicate it from a backyard or area since the seedbank can be quite large. So, if you find stiltgrass in your yard, start pulling now but know that you’ll likely have to pull them up again next year.
Garlic mustard is another invasive you can root out by hand if the infestation is light or scattered. Make sure to pull the entire root and not just cut the plant back. Cutting a flowering plant will allow it time to resprout from the roots. This is problematic if the area of growth includes native spring ephemerals such as yellow trout-lily or spring beauty. Garlic mustard’s monoculture nature shades out other plants and dominates the growing area. It outcompetes other plants for nutrients and resources and even releases allelopathic chemicals that can kill mycorrhizal fungi.
Of all the invasives we can find outside there is one that is the biggest thorn in my side (pun intended) and that is Japanese barberry. Barberry forms dense stands that can reach six feet high and multiple zig-zag branches that are extremely difficult to trim back. And trimming is a must if you’ll have any hope of getting to the roots without being jabbed by the hundreds of needle-thin thorns along each branch. Barberry is quite a beast, for sure. These beast-like qualities make it a perfect habitat for white-footed mice which tend to be Lyme disease reservoirs. Added to the list of problematic features is Japanese barberry’s unique self-created micro-climate that supports blacklegged (deer) ticks. Yes, this plant creates its own perfect habitat for deer ticks, the main source of Lyme disease. Mice find shelter and protection from predators within the safety of barberry. Deer ticks travel on their mice hosts to new homes within a barberry
bush and set up shop. As hikers and woodland creatures pass through barberry-invaded areas, deer ticks latch onto new hosts and spread disease. It’s a viscous cycle.
So, how do we stop barberry? We do our best. It’s an incredibly hardy plant, unfortunately. It’s shade, drought, and cold tolerant so extreme winters won’t have the effect one might hope for. But it can be removed using a weed wrench or similar tool. Be sure to remove the plant entirely because new growth can come from rhizomes and roots. Don’t forget to wear protective gloves along with clothing to cover exposed skin. The thorns on a Japanese barberry are fierce.
One of the prettier invasive plants we find at Strawberry Hill is mile-a-minute, so called because it can grow up to six inches a day. It produces a large tangle of thin vines that smother other native vegetation by blocking sunlight. Like English ivy, mile-a-minute can weigh down its competition until fragile stems break and plants die off from lack of light. And yet, it also produces a crop of striking blue-purple berries that stand out from the seas of green. The berries are dispersed after been eaten by a variety of wildlife and spread via elimination.
Interestingly, mile-a-minute berries are buoyant and can be spread via waterways for some time after being detached from their stems. They remain buoyant for a little over a week and so can travel long distances down creeks and rivers. They’re able to spread over larger areas by not being entirely dependent upon wildlife for dispersion. That’s great for mile-a-minute but bad news for us fighting an infestation of it. Fortunately, mile-a-minute requires less drastic eradication measures than other plants. Mile-a-minute can be pulled by hand and tossed aside to dry out and compost. Be sure to wear gloves and long sleeves, though. There are tiny, recurved barbs on the undersides of leaves.
Fighting the spread of invasives is a time-consuming process that takes patience and teamwork. At Strawberry Hill, we designate certain days each year for targeting specific areas and plants. It’s an ongoing battle that will last for years. But is it worth it? Yes, absolutely. We do our best to give our native flora and fauna the best fighting chance. We tackle the barberry, mile-a-minute, and so many more when and where we can. We don’t get them all, unfortunately.
Hope isn’t lost, however. Ever year brings new ideas, new methods – sometimes mechanical and sometimes biotic. As the seasons change and weather patterns shift, we may see some of these invasives die off on their own or become more manageable. For now, we’re donning our gloves and getting to work.
Anne Gageby is the Environmental Education Manager of the Strawberry Hill Foundation. Strawberry Hill inspires stewardship of our natural world by
connecting the community with educational opportunities.
Learn more by visiting StrawberryHill.org.
