(Lonicera japonica)

Description: A perennial, twisting vine with opposite leaves that can be deciduous or evergreen. New growth will have red, fuzzy stems, whereas older stems appear tan. The flowers are white, late spring into summer, then turn yellow and bear a sweet-smelling fragrance. Black fruits develop in the fall.

Impact: This invasive was introduced in New York in the early 19th century as an ornamental that didn’t become a problem until nearly two centuries later. It’s main impact is how fast it grows, twisting and climbing over native grasses, native shrubs and even into trees. If not controlled, a mature stand of Japanese honeysuckle can girdle, choke and kill woody vegetation. Although the berries provide a food source for birds, the nutritional quality of the fruits is poor.

Management: Young shoots (this year’s growth) can be removed by hand and should be removed before June. Large swaths can be controlled with a combination of mowing (once in early summer and again in late summer) and painting stems with a topical herbicide. Mowing alone can control the invasive after multiple years. Management should occur before the plant fruits in the fall.

Japanese Knotweed

(Fallopia japonica)

Description: This plant has large, heart-shaped leaves and jointed, hollow stems that resemble bamboo shoots. Its ability to grow over six feet by summertime adds credence to being called “bamboo” by residents. They develop large clusters of white flowers by August, although they do not reproduce by seed.

Impact: Japanese knotweed grows so rapidly that they prevent just about anything else from growing near them. But the roots (rhizomes) are the real danger, as even a single splinter from the rhizome will regenerate the plant the following season. Shredding or composting dead knotweed, as well as driving over treated areas, can contribute to its spread throughout the Island.

Management: Management is possible, but will take multiple summers to reduce knotweed on your property to manageable levels. They key is reducing the plant’s storage of food in the root system. Cut or mow down plants in June to keep regrowth short. By August, apply foliar herbicides to reduce the plant’s ability to store energy in the winter. Plant material should be bagged or burned, not composted. Continue these steps each summer as you starve out the root system and create space for your plants.

Autumn olive

(Elaeagnus umbellata)

Description: The olive’s leaves can be seen from a distance by their silvery sheen. Autumn olive has green on top and silver underneath, whereas Russian olive is entirely silver. All leaves appear scaled when up close. Young stems are silvery with brownish or orange scales that make them appear speckled. Some stems may bear large thorns. They have fragrant, yellow flowers in the spring and develop speckled red berries in the fall.

Impact: Both olives alter the chemistry of the soil where they grow, changing the kinds of plants that can enter and grow in the community, and helping the olives to persist. They also shade out younger trees by retaining their leaves into late fall. The leaves are undesirable by herbivores, including deer, and although the fruits are eaten by wildlife, they provide little nutrition.

Management: Since the tree spreads widely by seed, removing the plants before they fruit will help limit their spread. Cutting or mowing without herbicidal treatment, however, will only encourage regrowth in autumn and Russian olives. Paint cut stems when possible. Foliar sprays can be used in early spring, when the plant is leafing, or in late fall to minimize damage to native vegetation.

Oriental Bittersweet

(Celastrus orbiculatus)

Description: This deciduous vine has rounded or teardrop-shaped leaves with toothed edges that become glossy in summer and yellow in fall. The younger stems often appear to have spots or bumps. They produce green berries by July that turn yellow by August, orange-red by fall, and persist into winter.

Impact: Like porcelain berry, oriental bittersweet grows densely, preventing new plants from growing. It can girdle, strangle and eventually kill the trees they cover. Oriental bittersweet has replaced nearly all our native American bittersweet in New England.

Management: Killing the plant before it fruits is important. Younger vines can be removed by hand; look for the orange taproot to ensure you’ve removed the entire plant. Older vines need to be cut down or sawed to the base of the stem and painted with herbicide. Cutting back the vines before they fruit during the summer and applying herbicide in the fall or spring is also effective.

Black Swallow-wort

(Vincetoxicum nigrum)

Description: These vines have shiny dark green leaves that are oval-shaped when mature, with stems that tend to twine around one another. The plant has very small, purple flowers with five petals. Swallow-worts develop milkweed-like pods by August that turn brown and split open in the fall, releasing fluffy seeds that are dispersed by wind. Unlike milkweed, however, they do not produce milky sap.

Impact: Black swallow-worts grow rapidly in open fields and roadsides where there is sun, pushing out native plants. The plant secretes toxins that prevent other plants from growing near them, as well as being toxic to livestock and pets. Of chief concern is its effect on the monarch butterfly, which recognizes the plant as its primary plant host, milkweeds. When monarchs lay their eggs on swallow-worts, their caterpillars eat the plant and die. Swallow-worts grow in habitats shared by milkweeds, outcompete milkweeds and may lead to a decline in monarch butterfly populations.

Management: Control depends entirely on removing swallow-worts before they can reproduce seeds. Cutting down to the stem and painting with herbicide is effective, but cutting or mowing without applying herbicide afterwards will only encourage regrowth. With large infestations, foliar herbicides can be used in early June and again in August. Seed pods should be removed and either burned or bagged, not composted. Management of black swallow-wort may be necessary for multiple summers to deal with younger shoots, but it will be much easier to handle after the initial treatment.

Porcelain berry

(Ampelopsis brevipedunculata)

Description: Public enemy number one! This woody vine resembles grape leaves early in summer, but mature leaves will develop deep lobes. The vines can be broken easily by hand, while grape vines are very difficult to snap without tools. As the name implies, porcelain berry produces brilliant berries in late summer and fall that resemble porcelain, and one of the reasons it was introduced into the horticulture trade until it became invasive.

Impact: Porcelain berry forms thick mats in open fields and forests, covering plants at such a rate that they can rapidly block out sunlight and kill the plants underneath. Birds will also eat the berries during their migration, but the fruits are not as nutritious as native plants and so birds have to make more frequent stops to refuel.

Management: A large, thick mat of porcelain berry can often be traced back to a single root, and killing the taproot is key. You can easily pull this year’s growth out of trees by hand, and cut down towards the base of the stem with trimmers or loppers. Either remove the taproot through digging or painting the cut stems with herbicide to kill the plant. Removing porcelain berry before it fruits will help reduce regrowth.