At this time of year most of us have made a few trips to the local nursery to find some new items to spruce up our homes landscaping. One of the last things most of us consider is if our new planting is an invasive species or something non-native to our area that could actually harm or starve out our natives. Most of the common plant species thriving in the United States came from somewhere else originally, mostly Europe or Asia. The same goes for most invasive insects that are harming our natives. While they are often considered to be beautiful and desired additions, many of these plants spread rapidly in an environment that has not evolved to keep its growth in balance naturally. If not controlled an invasive species of plant can take over and harm or prevent native species from surviving.
Below is a quick list of some of the top invasives in North America. How many can you find in your own backyard?
Kudzu - Pueraria montana
Photo Citation: Peggy Greb, USDA Agricultural Research Service, Bugwood.org
Commonly seen growing as a high climbing, rapidly growing vine throughout the southeastern United States, the perennial known as Kudzu originally hails from Asia and was introduced in 1876. The United States Department of Agriculture estimates that kudzu spreads up to 150,000 acres annually and The Forest Service estimates that the weed spreads by 2,500 acres per year. Either way this invasive is capable of covering anything in its path, from trees, fences, and other permanent structures. When a tree or shrub is covered by Kudzu, the Kudzu usually wins and the "host" tree or shrub is often killed or significantly degraded. Flowering Kudzu is a fast-growing vine/legume with a grapelike odor and deep green leaves.
Image Citation: Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org (Kudzu overtaking native plants)
English Ivy - Hedera helix
Image Citation: Randy Cyr, Greentree, Bugwood.org
How many of our Grandmothers had a patch of English Ivy in their yards? (Mine did for sure!) English Ivy was originally brought to America by early settlers/colonists who sought to recreate the charms of their homeland. In this new environment English Ivy quickly became invasive, destructive and covered (even toppling) trees, low growing native species and climbing (charmingly) up the walls of houses. This one can be bought as a "houseplant" still even though it is restricted in most parts of the country as highly invasive.
Wisteria - Wisteria sinensis
A native of China, Wisteria is beautiful, fragrant and waterfalls over anything it covers. The beautiful Purple curtain like flowers are one of the biggest reasons so many fall for the beauty of Wisteria. Beware of planting Wisteria on your property, it grows so vigorously that it can quickly become difficult to manage. Like English Ivy, Wisteria has the ability to overtake anything in its path even killing mature canopy trees.
Image Citation: Chris Evans, University of Illinois, Bugwood.org
Barberry
This one is quite surprising as Barberry is commonly used as a shrub by many landscapers. I have some planted in various locations in my own yard but am very careful to keep them trimmed and under control. Believe it or not both common barberry and Japanese barberry are banned from sale in many areas of the United States (Not yet the Mid Atlantic region where we live). Originally introduced in the late 1800s, not only is it invasive, but it also provides an ideal hiding place for deer ticks which are a carrier of Lyme Disease.
Image Citation: Britt Slattery, US Fish and Wildlife Service, Bugwood.org
Butterfly Bush - Buddleja davidii
This one is another that is surprising as this can be found at most nurseries and even some big box stores this time of year. Butterfly bush offers much-needed nectar for many pollinators like butterflies and bees, but it is also considered an invasive or noxious weed in many states. Butterfly bush is known to push out native species and spread into uncultivated areas where it is not wanted. If not trimmed frequently Butterfly Bush can overtake an area in a single growth season.
Image Citation: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Purple Loosestrife- Lythrum salicaria
Purple loosestrife is a beautiful but aggressively invasive and hardy perennial. It is most commonly the cause of native plant growth restriction in natural and disturbed wetland areas. Once established it most often out competes and replaces native grasses, sedges and other flowering plants that would provide more nutrient rich sources of food for native wildlife. Originally introduced in the Northeast United States and Canada in the 1800's for medicinal and ornamental uses, it can now be found growing wildly in every state except Florida.
Image Citation: L.L. Berry, Bugwood.org
Norway Maple
Norway Maple is a vigorous grower and an adaptable species loved by many homeowners. Norway Maple surprisingly are also on the invasive plant list in many states. The Norway's shallow, dense root system often competes with lawns, other landscape plants and hardscaping causing not only annoying roots that can trip you, a bumpy mowing process and even lifting sidewalks and shifted retaining walls.
Image Citation: Rob Routledge, Sault College, Bugwood.org
Japanese Honeysuckle -Lonicera japonica
Honeysuckle has been used for decades along highways for effective erosion control. Japanese honeysuckle however can cause more harm than good by threatening native plants, it is famous for hoarding light, space, and nutrients in an established area suffocating out all of the native weaker plantings.
Image Citation- Chuck Bargeron, University of Georgia, Bugwood.org
Black Locust -Robinia pseudoacacia
Black locust spreads quickly, and is also short lived. Its branches are brittle and break easily when exposed to high winds. As a result of its ability to propagate quickly, it is considered invasive and is on the do-not-plant list in many areas throughout the country. Even so, it is still commonly planted by many commercial landscape firms on roadsides and within communities.
Image Citation: Richard Webb, Bugwood.org
Bittersweet-
This woody, perennial vine is native to Asia, and although it has beautiful berries in winter, it is considered an invasive species due to the way it starves out otherwise successful native plants.
Image Citation: Chris Evans - University of Illinois - Bugwood.org
Japanese Knotweed
Introduced to the United States from East Asia in the late 1800s, Japanese Knotweed has been considered problematic since the mid-20th century. It spreads quickly, crowding and shading out native vegetation.
Image Citation: Randy Westbrooks, Invasive Plant Control, Bugwood.org
Common Buckthorn
Like so many invasive species, Common Buckthorn was introduced to this nation's gardens by well-meaning botanists in the late 19th century. Besides crowding out native shrubs, it plays host to many pests, and the decomposition of its leaf litter can change the pH of the surrounding soil, which can cause problems for other nearby plants.
Image Citation: Jan Samanek - Phytosanitary Administration - Bugwood.org
Dame’s Rocket
Dame’s Rocket, with its fragrant white, pink or purple flowers blooming in spring, has long been a traditional garden favorite. But it is an invasive species, and no matter how beautiful, it has the potential to damage entire natural ecosystems.
Image Citation: Leslie J. Mehrhoff - University of Connecticut - Bugwood.org
Burning Bush
Known for its bright red, fall color, burning bush is a popular landscaping shrub throughout North America. It has many invasive traits, however, that allow it to spread aggressively. It’s not recommended for planting near uncultivated areas, and may end up on official invasive species lists in the near future.
Image Citation: Richard Webb - Bugwood.org
Giant Hogweed
Giant hogweed is not only on invasive species lists, it is officially classified as a noxious weed. Though it was originally cultivated as an ornamental plant, contact with its sap can cause terribly painful burns, scarring, and even blindness.
Image Citation: Terry English - USDA APHIS PPQ
