Invasive non-native plants are species that have been introduced to an area from another continent, or another part of a continent, that reproduce so rapidly that they crowd out native plants, causing economic (reduction in agriculture harvests as well as the cost to remove the plant) and environmental damage (loss of habitat, diversity).
When found in smaller numbers, such as in a lawn or garden, hand-pulling, and in some cases, digging out the roots, should help to prevent the plant from spreading. (Be sure to put the pulled plants in black bags so the plants die.) If the plant is on public land, such as a park or state forest, please alert the person in charge of that area.
Here are five plants that are of particular concern in the Chesapeake Bay watershed. Can you match them with their description?
(Alliaria petiolata [Bieb] Cavara & Grande)
(Microstegium vimineum (Trin.) Camus)
Wavy Leaf Basketgrass
(Oplismenus hirtellus ssp. undulatifolius)
1. This deep green, trailing grass with rippling waves across its flat blades (0.5- to 1-inch wide) is native to southeast Asia. It spreads rapidly, through root nodules on its short, hairy, horizontal stems as well as sticky seeds. It is so successful at outcompeting native species, that it is able to create a monoculture over large areas within a few years if left unchecked. It has no habitat value, so not only do native plants suffer, but the animals dependent on those plants as well. Removing the plants before mid-August, when its seeds spread, is the most effective way of eradicating this plant.
2. This trailing vine is also known as devil's tearthumb because of the recurved barbs that are found on the stem and underneath its triangular, light green leaves. A cuplike leaf, called an ocreae, surrounds the stem at its nodes. The ocreae is where the plant's small white flowers, and later, deep blue fruits, emerge. Its seeds are spread by birds, ants, small rodents and deer. This vine quickly grows over plants, blocking out the sun, which impairs their ability to photosynthesize, stressing these plants and killing them if it is not removed. Wear gloves when pulling out this plant. Recently, advances have been made in controlling this plant through the introduction of a weevil from its native home. The weevil is host-specific. It only eats this plant, and dies off when the plant does.
3. This slow-growing grass has 1- to 3-inch, asymmetrical lance-shaped leaves. It can reach a height of 2-3.5 feet. The midrib of the leaf is shiny with a line down the center slightly to one side. Stalks of tiny flowers appear in late summer, followed by dry fruits. This plant crowds out native species. It is a particular problem in areas where there are large numbers of deer, who shun the plant and instead eat the few plants that managed to survive this species' invasion. This is best pulled in midsummer before it goes to seed. Pulling too early in summer may actually help to germinate seeds from the previous season by disturbing the soil.
4. Crush the toothy, heart-shaped/triangular leaf of this plant and your nose will tell you how this European native got its name. It is a biennial plant. The first year, its leaves grow close to the ground. It stays green through the winter and the next year grows 2-4 feet tall in early spring, producing clusters of white flowers, each with four petals that produce a cross. This plant is a threat to many native wildflowers, which do not sprout quite as early, nor as tall as this plant, which outcompetes them for sun, moisture and nutrients. It also releases harmful chemicals that kill soil fungi used by oak seedlings to take up nutrients. This plant is best pulled by May or early June before it goes to seed in late June or July.
5. This spiny shrub from Japan has small oval leaves that can be green, bluish green or reddish purple and can grow 2-8 feet. It bears pale yellow flowers and bright red berries that appear in fall and last through the winter. It forms dense stands that crowd out other vegetation. It is spread through birds and animals that eat the berries. Research is also showing there is at least a five-fold increase in the risk of lyme disease in areas where this is the dominant plant. Small plants can be pulled by hand, while larger ones will have to be dug out. Where stands are too dense, repeated cutting may be needed.
1. Wavyleaf Basketgrass
2. Mile-a-minute (photo on page shows the effects of the weevil)
3. Japanese Stiltgrass
4. Garlic Mustard
5. Japanese Barberry