A PHOTO LIBRARY OF SOME COMMON INVASIVE PLANTS

Rewilding a piece of land is a multi-step process. Before you can plant an area you need to know what plants are currently growing there, and decide what to do about them.

In a suburban area like Westchester County, where the natural ecosystem has been fragmented and subjected to a lot of disturbance, many of the wild plants are aggressive, non-native invaders that grow opportunistically in disturbed locations. Identifying and removing these invaders is usually the first step toward gardening a new area. To help you identify the most common invasive plants in our area, we have put together this visual guide.

The best practice is to learn to identify the plants when they are young. At this stage they are easy to pull up. If it is too late for that, you will need to do more work to get rid of them, such as deep digging or repeated defoliating. Selective use of herbicides is a measure many people resort to because some of these species are so hard to kill. You will need to decide for yourself whether you are open to selective use of chemicals, or committed to organic practices. To learn about managing the different invasive species, we recommend you consult the very thorough manual produced by the non-profit research center Hudsonia: Best Management Practices for Priority Invasive Plants in the Lower Hudson Valley.

Oriental Bittersweet

This fast-growing woody vine is hard to keep off your property because the seeds are spread by birds. Bittersweet grows in both sun and shade and can strangle trees. If cut back in the spring it will resprout vigorously. Better to cut it back midsummer, better yet to cut it back it weekly until it gives up the fight. Best of all is to catch it young, when you can still pull it up easily and get rid of it. Young bittersweet plants may be hard to recognize because they are not very distinctive, but their orange roots are hard to mistake, so after some trial and error you will probably get to know this adversary all too well.

Porcelainberry

This relative of wild grape grows very fast, very tall, and will smother everything in its path. It is the one you have seen by the side of the highway covering entire trees. Try to catch it young as bigger plants are hard to dig up. The beautiful turquoise and purple berries are spread by birds, so even if you think you have no porcelainberry in your yard, remain vigilant. If you find you cannot dig it up, at least keep it cut back so it does not set seed or strangle its neighbors.

Japanese Knotweed

This hollow-stemmed weed comes up from the ground every spring and can reach 8 feet tall. It spreads clonally from underground roots and can colonize an entire area. If your patch is small, persist until you have dug all of it out, and keep checking to make sure none has survived to recolonize. If your patch is larger, containment is a more realistic strategy. If it is in a location where it can be mowed, that may be something to try. Repeated whacking back will weaken it though probably not eliminate it.

Black Swallow-wort

This is one to prioritize: Remove it as soon as you find it. Do this by digging up and disposing of the root crown and all roots that radiate from it. Black swallow-wort is a vine from the milkweed family, native to Europe. It spreads quickly by underground rhizomes, overtaking and suppressing other vegetation. The vine has small, almost black flowers in summer and long thin milkweed-like pods in autumn, so it can also spread by windblown seed. If you see seed pods, cut them off and discard them into the trash before they ripen. Do not compost, as seeds can ripen after a plant has been pulled.

Multiflora Rose

This sprawling vine is hard to tackle because of its many nasty thorns. If you can get past the thorns, digging it up succeeds in killing it.

Wineberry

This invasive berry plant will spread by rooting where its stems touch the ground. Although its berries are delicious, you may want to contain or eliminate it.

Japanese Barberry

This is a particularly noxious invasive because of its tendency to colonize the woods, forming large stands. Barberry seems to have no trouble growing in shade and particularly likes our wetlands. It provides shelter for woodland mice, which harbor ticks, and a link has been shown between barberry cover and Lyme disease. This is one to dig up and get rid of. It is thorny and unpleasant, but digging it up does kill it.

Burning Bush

This is a much-planted ornamental for its magenta foliage in fall. Unfortunately it is very invasive and will spread into woodlands, displacing native shrubs. It is not hard to cut down though it will try to make a comeback and you will need to keep after it for a while.

Mugwort

Native to Eurasia, Mugwort spreads aggressively by shallow underground rhizomes and grows up to 5 feet. It will take over meadows and other sunny areas. It's relatively easy to pull because of its shallow roots, but repeated pulling is necessary because any small piece of root left in the ground will regenerate. Repeated low mowing, though unlikely to eliminate mugwort, will discourage it and encourage the growth of grasses, clovers and other sun-lowing lawn and meadow plants, resulting in greater biodiversity in the area.

Japanese Stilt Grass

This is the light green grass you see oceans of in moist locations in our woods. It competes with native vegetation and reduces germination and seedling growth. Because stilt grass is an annual, the best time to attack it is right after it blooms, and before it sets seed. At that time you should mow it or pull it. Mowing or weed whacking is best to avoid disturbing the soil. Because stilt grass seeds can last up to 7 years in the ground, this will be a multi-year effort, but you should be able to reduce or nearly eliminate it over time. Snowplows, automobile tires and other construction equipment move the seed from one location to another, so it will probably make its appearance near your driveway or house if it’s not there already.