Invasive Herbaceous Plants
Canada Thistle (Cirsium Arvense)
Canada thistle is a widely distributed perennial plant that can grow up to five feet tall. Its leaves have sharp spines along the edges. Canada thistle grows in various habitats with full or partial sun and is often found in disturbed areas such as roadsides, trails, pastures, and recently flooded areas.
Canada Thistle impacts:
Creeping Charlie (Glechoma Hederacea)
A short, horizontally growing plant with square stems, round-toothed leaves, and small purple flowers. When crushed, it has a faint mint smell.
Creeping Charlie impacts:
Crown Vetch (Coronilla Varia)
Crown vetch is a perennial herbaceous plan. Its stems trail over other plants and can grow 2-6 feet long. Crown vetch plants are brown in winter and early spring and can be visible as brown patches on the landscape.
Crown Vetch impacts:
Garlic Mustard (Alliaria Petiolata)
Garlic mustard has two different appearances depending on whether it is one or two years old. First-year plants are a low-growing circular arrangement of kidney-shaped leaves with scalloped edges called rosettes. In its second year, plants shoot up a 12-36 inch stem that will develop small white flowers at the top. If crushed, the plant smells like garlic.
Garlic Mustard impacts:
Leafy Spurge (Euphorbia Esula)
Leafy spurge is an herbaceous plant that grows two to four feet tall and has flowers that are a distinct yellow/green color. When broken, the plant's stems, flowers, and leaves emit a white milky sap.
Leafy spurge impacts:
Poison Ivy (Toxicodendron rydbergii)
Western poison ivy is a smallish, non-climbing shrub, usually about knee high, with a single stem and only a few stubby branches or no branches at all.
Poison Ivy impacts:
Western poison ivy often forms colonies, sometimes 20 ft (6 m) or more across. They grow quickly and can spread aggressively, especially in damaged habitats. This is certainly the case on roadsides, ditch banks, utility rights-of-way, and old fields. It is also notoriously adept at encroaching into mowed lawns from adjacent woods.
Poison Ivy Infestation photo poisonivy-academy.com
Flowers of Poison Ivy, photo David Beaulieu
Fruit of Poison Ivy, photo Theodore Webster
Leaflets of Poison Ivy, photo massaudubon.org
Spotted Knapweed (Centaurea Maculosa)
Spotted knapweed is a biennial or short-lived perennial herbaceous plant growing 2-3 feet tall. Basal leaves form a rosette the first year, growing one to twenty wiry, branched stems during the second year.
Spotted Knapweed impacts:
Wild Parsnip (Pastinaca sativa)
Wild parsnip spends one or more years as a clump of low-lying leaves with no vertical stem. The following year, it grows up a flowering stalk, blooms, and then dies. It is 6 inches tall in the rosette stage and 4 feet tall in the flowering stage, with yellow flowers.