Invasive Plant Guide

Invasive plants crowd out other species and smother native trees and shrubs.

Bag those berries!

Invasives yielding berries require careful disposal in large black bags in the trash, not in the garden waste area at Holly Hill. Seeds of an invasive are naturally dispersed by animals , wind, birds and humans. Invasive species have no natural enemies to limit reproduction so they usually spread rampantly.
DO NOT use invasive vines and berries in holiday decorations or outdoor wreaths. This can support the spread of seeds to new areas.

Japanese Barberry
(Berberis thunbergii)

Eliminate Barberry and you can eliminate 80% of the Lyme-infested ticks on your property, according to recent research by CT scientists.

Shrub with small, usually green leaves (also red varieties) and many small thorns. Flowers in mid- spring and produces large numbers of red berries that can have a 90% germination rate. It spreads by seed and by vegetative expansion (branches touching the ground that root to form new plants.)

Japanese Knotweed/Mexican Bamboo
(Polygonum cuspidatum)

Distractingly pretty, this perennial herbaceous shrub often grows to 10 feet tall, flowering in Fall. Chases away other under-story plants and is extremely hardy. Cut back often and it will eventually die.

Japanese Stilt Grass
(Microstegium vimineum)

This grass reaches several feet and is found from one end of Greenwich to the other.  It crawls into lawns, gardens, plants and even the darkest woods.  Stilt Grass turns brown in September.

Photo: National Park Service

Mile-a-Minute Vine
(Persicaria perfoliata)

This annual vine continues to invade Greenwich and surrounding areas.  It can grow six inches a day, forming a dense mat which suffocates your trees and shrubs.

Photo: Leslie J. Mehrhoff

Multiflora Rose
(Rosa multiflora)

Perennial shrub flowers beautifully but grows very aggressively in all directions, smothering all nearby plants and flowers. Strong thorns make disposal challenging.

Photo: USDA National Invasive Species Information Center

Oriental Bittersweet
(Celastrus orbidulatus)

Prized in Fall floral designs for its beautiful yellow and orange berries, Bittersweet strangles everything.  It often coils about other invasive vines. Seeds are spread by insects, wind, humans and birds.

Photo: Bittersweet berries in the fall by Mn Dept of Agriculture

Poison Ivy
(Toxicodendraon radicans)

This Native Nuisance is perhaps our most common woody vine.  In Spring, three reddish leaves emerge, maturing to green, often glossy.  Its leaves turn vivid red in early Fall.  All parts of the vine may cause the famous rash all year.  Look for a furry vine climbing trees.  To learn more Outsmarting Poison Ivy and Other Poisonous Plants by FDA.

Photo: National Park Service

(Ampelopsis brevipedunculata)

Masquerading as very pretty cultivated grape, this perennial invader of open wooded habitats shades out other plants and consumers resources.  Grows and spread quickly in areas with high to moderate light.

Photo: Virginia Native Plant Society

Winged Euonymus / Burning Bush
(Euonymus alatus)

Sprouts green leaves in Spring, turning bright red in Fall. Seeds land everywhere, creating a monoculture in shade and sun.  Easily identified by its very unusual bark.

Photo: Invasive.Org