5 common local plants that didn’t evolve in the Potomac River region
/Become an expert at spotting—and stopping—these ecosystem disruptors
Image courtesy of kleinfreund via Flickr (used under CC BY-SA 2.0)
Take a walk around your neighborhood, and you might find a plant that did not evolve locally—or, more likely, you'll find several. These plants, sometimes called invasive, are plants that are not indigenous to a region. They’re brought in (sometimes on purpose, sometimes not) from other states, countries, or continents, and are harmful to the local ecosystem.
Invasive plants might not have natural predators and can quickly take over the landscape, causing harm to locally-evolved plants that also need sunlight and soil nutrients. This can lead to indigenous plants dying, impacting the ecosystem and the wildlife that depend on local plants for nourishment and shelter.
What's more, invasive plants are bad news for our local rivers and streams.
They can kill locally-evolved trees—even large, well-established ones—which are crucial in the fight for clean water. Trees stabilize stream banks and prevent harmful sediment and pollution from entering waterways. They also keep communities cool and fight climate change with their carbon-capturing abilities!
There are dozens of plants in our area that did not evolve here. And some will surprise you. Learn how to spot 5 plants that disrupt local ecosystems and what you can do to prevent them from causing further harm.
Amur and Morrow’s honeysuckle (Lonicera maackii and Lonicera morrowii)
Image courtesy of Melissa McMasters via Flickr (used under CC BY 2.0)
The succulent smell synonymous with summer in our region is likely coming from an invasive plant.
How did it get here? Both varieties were imported in the 1800s for ornamental planting and soil erosion control. The same is true of the Japanese honeysuckle, which is the most common ornamental vine.
How do I get rid of it? Young plants can be pulled by hand; larger plants should be cut repeatedly. These tenacious plants may need herbicide application to be fully eradicated.
What should I plant instead? Locally-evolved honeysuckle, such as American fly honeysuckle, swamp fly-honeysuckle, and mountain fly honeysuckle.
English ivy (Hedera helix)
Image courtesy of James St. John via Flickr (used under CC BY 2.0)
It looks great creeping up the walls of an English manor, but the keyword here is ENGLISH. Here in the U.S., it doesn’t look so nice when smothering some of our favorite indigenous trees in places like Rock Creek Park.
How did it get here? It was brought over in the mid-1700s by European colonists. It's still widely sold in nurseries as an ornamental ground cover.
How do I get rid of it? Step 1. Don’t plant it! Step 2. Tell your friends, neighbors, family, coworkers, and strangers on the bus NOT to plant it!
Individual vines can be pulled when they are wet or can be raked up with a heavy duty rake. If it is already creeping up a tree, don’t pull it off the bark; you can damage the bark that way. Instead, use pruners to clip the vines around the base of the tree and then rake up the ivy on the ground. Be sure to dispose of the ivy, so it doesn’t re-root.
What should I plant instead? Try creeping phlox or Allegheny spurge for evergreen ground cover.
Princess tree (Paulownia tomentosa)
Image courtesy of Melissa McMasters via Flickr (used under CC BY 2.0)
Don’t be fooled by its beauty. It can overtake indigenous plants and trees in forests and along stream banks.
How did it get here? The princess tree was imported to Europe from Central and Western China by the Dutch East India Company and then on to North America in the mid-1800s.
How do I get rid of it? This tree is still commonly sold, so don’t buy it and tell your friends and family not to either. Young plants can be pulled by hand; larger trees must be cut down prior to seed formation.
What should I plant instead? Try a serviceberry. You can even make delicious muffins from the berries if you can get to them before the birds!
Common daylily (Hemerocallis fulva)
Image courtesy of John Munt via Flickr (used under CC BY-NC 2.0)
Them too?! They don’t call it common for nothing, but unfortunately, this popular flower forms dense patches that displace locally-evolved species.
How did it get here? Also known as a tiger lily, it was introduced in the late 19th century as an ornamental plant. It became ubiquitous in North American gardens because of its showy flowers, hardiness, and ability to spread; exactly what makes them such a dangerous ecosystem disruptor.
How do I get rid of it? Sorry to sound like a broken record but, don’t plant it! You can dig up existing plants with a shovel to loosen the root system and then remove the tubers. Make sure to dispose of them bagged and in the trash and NOT in your compost pile or they will come back.
What should I plant instead? Locally-evolved lilies! The Canada lily, wood lily, and Turk’s cap lily are all good options.
Japanese stiltgrass (Microstegium vimineum)
Image courtesy of NY State IPM Program at Cornell University via Flickr (used under CC BY-NC 2.0)
This is a tricky one because it looks like several native grasses. Be on the lookout for an asymmetrical leaf with a shiny midrib and a stilt-like growth form.
How did it get here? Whoops! This one was an accident. It likely escaped in Tennessee when it was used as packing material for porcelain in the early 1900s.
How do I get rid of it? Once you know it is not a native look-alike, you can pull it by hand. Don’t pull this plant if it is flowering because that will spread the seeds and do more harm than good. Instead, cut the plant back using a mower or weed whip. You may have to use herbicides if the infestation is bad.
What should I plant instead? Once you remove Japanese stiltgrass, you can plant indigenous plants suitable for the specific conditions. The Alliance for the Chesapeake Bay and U.S. Fish and Wildlife Service put together a handy guide for native plants for wildlife and conservation landscaping in the Chesapeake region.
Non-local and invasive plant FAQ:
How do I know what’s what?
The National Park Service and U.S. Fish and Wildlife Service puts out an easy-to-use guide to invasive species common in the Mid-Atlantic area.
Are all non-native plants invasive?
Nope! An invasive is a species that was taken out of its original environment and whose introduction into another environment, whether intentional or not, is likely to cause harm to local plants, economy, or human health.
The U.S. Fish and Wildlife Service says, “Non-native plants are fundamental to our lifestyle — most of our food crops, such as potatoes and wheat, are not native to the United States. Invasive species, however, are exotic organisms that have gone beyond being useful and have become harmful.”
Why do species that did not evolve locally outcompete species that are indigenous to the area?
Aside from lacking natural predators and pests, non-locally evolved species typically spread more quickly, have shorter generation times and extended growing seasons, and are able to grow in disturbed or polluted areas that other species may not be able to tolerate.
Doesn’t the addition of a non-indigenous species increase biodiversity?
Yes, but according to Vermont Invasives, this only happens if you are looking at the number of species in the short term. Plants that were introduced to an area will become “new” but they may also decrease the number of indigenous species over time as they compete for resources and remove them from a balanced local ecosystem.
Isn’t plants moving around part of a natural cycle?
Yes, plant populations will change as their native ranges change due to climate change, but this happens very slowly (over thousands of years). This gives other plants and animals time to adapt as well. If we speed up this process, we will decrease our local biodiversity without giving the entire ecosystem time to adapt.
How can I help?
Local organizations, like Rock Creek Conservancy, host invasive removal events in area parks. You can also become a Weed Warrior with Montgomery Parks, and, after some training, lead your own events!
