Top Five Invasive Plants in Rehoboth

          “What do you think these are?”

It was our first spring in our new home. My husband and I were enjoying a walk around the yard, when we came across a patch that was full of pink spear-shaped sprouts about an inch tall. Encircled by a wooden frame, they were clearly meant to be there, so we left the question unanswered and moved on, eager for more discoveries.

A month later, those tiny pink sprouts had become giants, with most stalks taller than my husband! We were fascinated by this bamboo-like plant. We loved it as much as the honeysuckle, hydrangeas, raspberries, daffodils, and other surprises our new home revealed as the seasons changed.

Within a few years, however, we started noticing our beloved “bamboo” was not being a good neighbor. Not only had it spread into the raspberry patch and crowded out the hydrangeas, but it had also emerged along the edge of the woods and was slowly creeping into the yard. There were other miscreant flora as well. A twining vine, whose orange berries fed the birds in the fall and winter, was choking its host tree like a boa constrictor. And that honeysuckle? It was running rampant all along our driveway, overtaking the daffodils.

A bit of research revealed that we had stumbled across one of the greatest threats to our natural environment: invasive species. Our “bamboo”? Japanese knotweed. The deadly vine? Oriental bittersweet. Japanese honeysuckle, Japanese barberry… our yard’s got it all and then some. I’m willing to bet yours does too.

According to the Center for Invasive Species and Ecosystem Health, a species is invasive if it meets three criteria: 1) it’s not native to its surrounding ecosystem; 2) it’s capable of propagating; and 3) it causes harm to the local economy, environment, or human population. Notice that simply being non-native doesn’t automatically make a species invasive. For example, many staples of North American agriculture, such as tomatoes and wheat, are not native to this continent, but have you ever seen a tomato plant choke a tree? Me neither.

When a plant (or animal) is plucked out of its native habitat and introduced across the world, local predators typically don’t recognize it as food, leaving it free to reproduce unchecked. The result is what we’ve seen playing out all over town and across the country: invasive plants decimating native species by blocking out the sun, hogging water and nutrients, and outright strangulation.

What can you do to protect your garden, yard, and town from this threat?

Let’s start with five of the most common invasive plants in Rehoboth and the best ways to get rid of them according to the CT Invasive Plant Working Group, along with some personal tips from Rehoboth Land Trust (RLT) members.

**A note about pesticides: While chemical pesticides should generally be avoided to prevent harming pollinators or contaminating soil, most invasive plants are so relentless that careful, selective pesticide use is often the most effective choice. Be sure to follow all instructions thoroughly, and never spray pesticides on plants that are in flower or carrying berries.

Japanese Knotweed

Habitat: Prefers riverbanks, but the ability to adapt to almost any environment and shade level is a common characteristic of invasive plants, and Japanese knotweed is no exception.

Reproduction: Rhizomes form dense underground mats that grow up to 10 feet deep and 30 feet long. Cuttings are able to take root, so be sure to dispose of these properly.

RLT Tip: Toss cuttings under a tarp until burning season – the stalks pop like fireworks when they burn, which is immensely satisfying. Roots need to fully dehydrate in the sun.

Most Effective Control Method: June - September: Cut and immediately paint glyphosate directly to the rim of the remaining stalk.

Best Pesticide-Free Control Method: If you catch the infestation early, pulling up the plants or mowing them can work, but you’ll have to do it every time you see new growth, which could be weekly throughout the spring and summer. It will probably take doing this a few years in a row before it’s gone for good. If it’s a mature colony that’s at least a couple years old, you’ve got a hard decision to make. Even if you cover the problem area with a tarp or weed barrier, the rhizomes will stay alive in a dormant state for up to 20 years!

Trivia: Japanese knotweed can grow up to three inches per day – both above and below ground.

Oriental Bittersweet

Habitat: If there are trees, fences, or poles, Oriental bittersweet will find them. In sun or shade, this vine can grow as long as 60 feet, with a diameter of up to 4 inches.

Reproduction: Its berries are eagerly eaten by birds, which then distribute the seeds. Everywhere.

Most Effective Control Method: June - September: Cut vines and immediately paint glyphosate or triclopyr onto the severed surface of the ends that are still rooted.

Best Pesticide-Free Control Method: Pulling and cutting at any time of year will stimulate new growth, so multiple passes will be required throughout the growing season and for a few years before it’s gone for good. RLT Tip: As much as you might want to, don’t yank bittersweet off of trees, as this can harm the already weakened tree. Cut the vine as high as you can reach, and eventually it will fall off. The same holds true if a thick vine is embedded into the tree: sever the vine at ground level and let it loosen and fall naturally.

Trivia: American bittersweet is a native vine, but is often mistaken for its Oriental cousin. It can be tricky to tell these two apart, since berries only grow on mature female plants. If you do see berries, Oriental bittersweet fruits all along the stem, while American bittersweet only fruits at the end of the stem.

 Japanese Barberry

Habitat: Shady forests, sunny fields, and everything in between.

Reproduction: Berries + birds = baby Japanese barberry.

Most Effective Control Method: April – October: Apply glyphosate or triclopyr to cut plants.

Best Pesticide-Free Control Method: Digging up plants at the roots can be effective at any time of year, but it will come back if you don’t get the entire root. Young plants can be mowed, but it will take several passes and perhaps a few years before it’s entirely gone.

Trivia: Ticks and mice love Japanese barberry because it increases soil humidity and ground cover.

Japanese Honeysuckle

Habitat: Just about anywhere.

Reproduction: Pollinators love the flowers, and birds love the berries.

Most Effective Control Method: September – October: This plant keeps its leaves longer than most native plants, so apply glyphosate to green leaves in the fall to lower the risk of harming other plants.

Best Pesticide-Free Control Method: Like Japanese barberry, digging plants up at the roots will work at any time of year, but it will come back if you don’t get the entire root. Young plants can be mowed, but several passes and a few years might be needed before it’s entirely gone.

RLT Tip: If you don’t get around to mounting your offensive until after the flowers have bloomed, be sure to at least treat yourself by sucking out the yummy nectar (before applying any pesticides, of course)!

Trivia: The best way to distinguish our native honeysuckle vines from invasive species is to break off a stem and look at the cross-section: if there’s a hole running through it, that’s an invasive honeysuckle; if it is solid, without a hole, it’s a native honeysuckle.

Multiflora Rose

Habitat: Most often found along edge habitats and roadsides, it thrives in poor soil and can survive even in full shade

Reproduction: Berries appear in late summer and remain throughout the winter, feeding local birds.

Most Effective Control Method: Pulling/digging up by the roots at any time of year, and applying glyphosate to cut plants May through October, are both effective control strategies, although multiple passes of pulling/digging may be required before it’s fully gone.

Trivia: A well-established plant in full sun can grow up to 1-2 feet per week in midsummer!

Invasive plants (and animals) are a major problem. Help stop their spread by using some of the methods listed above to snuff them out in your own back yard.

Everybody loves a good before-and-after picture! Share yours of clearing invasive plants from your yard on the Rehoboth Land Trust Facebook page.