Many invasive garden plants find their way into our landscaping by accident, but there are others which we may inadvertently invite. It usually starts innocently enough with some exotic ornamental plant, imported to North America for its unusual blooms, striking foliage, or other specific use. But in no time flat our carefully selected new garden guests can go as rogue as kudzu. These invasive species may crowd out other cultivated plants or, worse, escape from our gardens altogether. Depending on their level of success in the wild, they can displace important native species and fundamentally alter environmentally sensitive natural habitat. Discover 10 invasive garden plants to avoid, and (if it’s too late) how to get rid of them.
What makes a garden plant invasive?
Invasive garden plants are those species which prove to have some clear competitive advantages over other plants growing nearby. Some of these advantages include:
- Growing and multiplying rapidly, whether by producing many new shoots, releasing a prolific amount of seed, or spreading by underground rhizomes
- Thriving in a variety of growing conditions and throughout multiple hardiness zones
- Emerging very early in the spring or surviving beyond late fall and sometimes even into winter
- Lacking many natural insect or animal predators
Due to these and other advantages, invasive plants can threaten the ecosystem as a whole. By outcompeting native vegetation, invasive garden plants choke out biodiversity, and the insects, birds, small mammals, and other creatures which depend on specific natives for their food and shelter ultimately lose out.
Invasive vs. exotic plants
What we now know to be invasive garden plants were, in many cases, once just intriguing or potentially useful exotics. Sometimes also called “alien” or “introduced” plants, exotics are non-native plants that may be spread to an area intentionally or unintentionally. It’s worth noting that not all exotic plants are invasive.
That said, however, exotics can become invasive over time. For example, purple loosestrife—currently illegal to sell in many states—routinely appeared in catalogs like the 1951 “Seeds of Honey Plants Offered by Pellett Gardens.” Calling purple loosestrife a “promising bee plant,” the seed purveyors noted, “Some beekeepers have improved local bee pasture by sowing along streams and around ponds. The plant gradually spreads downstream.”
Well, maybe not so gradually. Turns out, a single purple loosestrife plant can generate well over two million seeds. Eventually, exotic purple loosestrife plants would be classified as invasive—moving into our native wetlands, displacing wildlife, and threatening agriculture.
Why can you still buy invasive garden plants?
Despite their aggressive tendencies, many invasive garden plants are still sold. According to a 2021 Frontiers in Ecology and the Environment study, “[Researchers] found that 61% of 1,285 plant species identified as invasive in the U.S. remain available through the plant trade, including 50% of state-regulated species and 20% of federal noxious weeds.”
In part, lack of uniform regulations from state to state and inadequate oversight and enforcement of those regulations may be to blame. “Regional regulation coupled with outreach to growers and consumers is needed to reduce the ongoing propagation of invasive plants in the U.S.,” the researchers noted.
10 Invasive garden plants to avoid
What follows are 10 common invasive garden plants that you should keep out of your landscape if at all possible. However, if you already have some of these, not to worry! We’ve also included invasive plant removal tips and potential native alternative plants to try as well.
1. Ribbon grass
This variegated form of reed canary grass (Phalaris arundinacea) historically has been used as a ground cover. With contrasting green-and-white-striped leaves, it’s an attractive addition to the garden, but it’s also an aggressive spreader—especially when planted in loose, moist soils. A native alternative to try: Ivory sedge (Carex eburnea)
Goutweed (Aegopodium podagraria), also known as ground elder or bishop’s weed, is one of the many invasive garden plants still being sold. Featuring pretty, green or variegated foliage and tiny white flower clusters, goutweed spreads prolifically via its vast network of underground rhizomes. A native alternative to try: Golden Alexander (Zizia aurea)
3. English Ivy
English ivy (Hedera helix) has distinctive, dark green leaves borne on vines which quickly swallow up shrubs and trees and can even damage your home’s exterior. Nothing to climb nearby? Then it spreads aggressively along the ground, shading out competitor plants along the way. A native alternative to try: Woolly Dutchman’s pipevine (Aristolochia tomentosa)
4. Lily of the valley
Although lily of the valley (Convallaria majalis) is a fragrant, early bloomer, it can wreak havoc in the understory of our forests. Another aggressive spreader, it displaces important spring ephemeral wildflowers which, in turn, support native bees, birds, and other wildlife. A native alternative to try: Solomon’s seal (Polygonatum biflorum)
5. Vinca, also known as periwinkle
Sporting glossy leaves and pinwheel-like flowers, vinca or periwinkle (Vinca minor) is one very tough ground cover. The plants are able to withstand a fair amount of trampling and stay low to the ground; however, they do spread far and wide. A native alternative to try: Canadian wild ginger (Asarum canadense)
Japanese barberry (Berberis thunbergii) has long been the go-to hedge for attractive fall color and long-term winter interest, because its leaves change color and it retains most of its shiny, red berries. Japanese barberry now has spread into our forests to displace important native plant communities. A native alternative to try: Winterberry (Ilex verticillata)
7. Chinese wisteria
A strong, woody climbing vine, Chinese wisteria (Wisteria sinensis) can live for 50 years or more and has made its way into our forests. There, it shades out new understory trees and eventually chokes out more established trees as well. A native alternative to try: American wisteria (Wisteria frutescens)
8. Purple loosestrife
Reaching five feet tall (and sometimes taller!) purple loosestrife (Lythrum salicaria) sends up lavender flower spikes which pollinators love. Remember, just one plant can produce more than two million seeds. As a result, purple loosestrife rapidly dominates the landscape. It’s an especially serious threat to wetlands. A native alternative to try: Purple blazing star (Liatris spicata)
9. Butterfly bush
Although butterfly bush (Buddleja davidii) does provide butterflies and other pollinators with nectar, this exotic shrub is now considered invasive—particularly in the Pacific Northwest. Also, if you’re looking to help monarch butterflies during every life stage—egg, larva, and adult—butterfly bushes alone won’t cut it. A native alternative to try: Swamp milkweed (Asclepias incarnata)
10. Chameleon plant
Native to southeast Asia, Houttuynia cordata is also called fish mint, chameleon plant, and rainbow plant, among other names. The popular ground cover has variegated leaves in shades of yellow, pink, and green, but it’s very aggressive and difficult to eradicate once it takes hold. A native alternative to try: Woodland stonecrop (Sedum ternatum)
5 ways to get rid of invasive garden plants
Whether you’re tackling noxious plants like kudzu vine and giant hogweed or you want to remove the last of that thorny Japanese barberry, you’ll need to use caution—and the right equipment.
- Personal protection – Sap from some of the plants you touch may cause contact dermatitis, so, put on gloves, long pants, and long sleeves first. Also, to prevent further spread of invasives, you can bag up and trash the plants you remove or bury them deep underground.
- Digging – You may be able to dig up shallowly rooted invasive garden plants with a shovel or hand trowel. However, if the plants spread by rhizomes it’s important to remove every piece you find.
- Snipping – Use garden pruners to cut back flower heads before seeds can set. For vines and woody shrubs, use shears to cut plants back as close to the ground as possible. Repeat as new growth sprouts to starve the root system and kill the plant.
- Pulling – Use a heavy-duty weed extractor or a weed wrench to uproot small trees, large shrubs, or plants with long taproots.
- Tarping – Tarping invasive garden plants like goutweed is effective but takes time. Begin by cutting the plants back to the ground, collecting the discarded trimmings. Place a tarp over the area, making sure it’s large enough to extend at least a foot or two beyond the perimeter of the invasive plant. The goal is to starve the plant of sunlight and capture heat to ‘cook’ it. The best time to lay a tarp is in spring leaving it on until autumn. However it may take several years to successfully eliminate the plant.
Other invasive garden plants to be aware of
Although by no means an exhaustive list, here are some other invasive garden plants you might encounter in your local garden shop or, sadly, already installed in your own landscape! Steer clear of these—or remove them if need be.
- Callery pear (Pyrus calleryana)—A relative of the ubiquitous Bradford pear tree, the Callery pear produces seeds which easily spread. The result? Callery pear groves which suppress and outcompete essential native species.
- Norway maple (Acer platanoides)—Norway maples likewise produce tons of easy-to-spread seed and also suppress competitor plant growth.
- Japanese honeysuckle (Lonicera japonica)—Because birds can’t resist the berries from this tough, woody plant, it quickly takes over to grow as a shrub or by vining its way up established trees.
- Chinese privet (Ligustrum sinense)—Chinese privet has become incredibly widespread since it can tolerate just about any kind of growing conditions. Birds also readily scatter its seeds.
- Winter creeper (Euonymus fortunei)—This evergreen ground cover forms thick mats on forest floors and grows high into tree canopies, shading out understory growth and weakening mature trees.
Final advice on getting rid of invasive garden plants
When left unchecked, invasive plants can run amok within our gardens and beyond our garden borders, too. Whether imported on purpose or brought in by accident, some exotic plants enjoy special advantages which give them an edge over our native plants. For instance, some invasive garden plants produce copious amounts of seed, while others have few natural predators in our local landscapes. As such, these plants threaten the health of our forests, wildlife, agriculture, and more. Now that you know more about which plants are truly invasive and how you can remove them, you can help to stop, or at least slow down, their spread.
For more information on native plant alternatives, be sure to check out these articles:
- Native white asters for the garden
- Plant milkweed to help monarch butterflies
- Light up the late season garden with rudbeckias
- Learn how to grow ‘Purple Dome’ aster