A Regional View of Invasive Plants

How does what I do in my yard, on my land and in my garden affect what plants invade our forests and grasslands?¬† What has happened on the land where you live (its history of use), and what you plant now, can have a long-lasting impact. Land use legacies appear to play a large role in the patterns of invasive plants and the impacts they may have. The progression of time shows how well a plant manages to spread, and …

Aegopodium podagraria, Bishops Goutweed


Invasive Species: Aegopodium podagraria, Bishops Goutweed

Bishops goutweed is an invasive creeping perennial that can grow to 3 ft. (1 m) tall. The compound leaves are alternate and have sheathing bases. The leaves at the top of the stem are smaller and have fewer leaflets. The leaflets are dentate and 1 to 3 in. (2.5 to 7.6 cm) long. Blooming occurs in June, when a flat, 2 to 4 in. (5 to 10 cm) wide cluster of small white …

Acroptilon repens, Russian Knapweed


Invasive Species: Acroptilon repens, Russian Knapweed

Russian knapweed is an invasive¬†perennial forb that can grow to 3 ft. (1 m) in height. Stems originate from a basal rosette of leaves. The rosette leaves can be unlobed to very lobed and are 2 to 4 in. (5 to 10 cm) long. Stem leaves are oblong, pinnately lobed to entire, and up to 6 in. (15.2 cm) in length at the base of the stem; they become smaller and less …

Securigera varia, Crownvetch


Invasive Species: Securigera varia, Crownvetch

Crownvetch is a low-growing, invasive, herbaceous vine that usually forms thickets up to 3 ft. (0.9 m) in height. The leaves are pinnately compound with 9 to 25 pairs of leaflets and a terminal leaflet. Leaflets are 0.75 in. (1.9 cm) long. Flowering occurs in the summer. The fragrant, pea-like flowers are white to pink to purple and resemble a large clover flower. Crownvetch reproduces and spreads rapidly by rhizomes as well as seeds. …

Centaurea calcitrapa, Purple Starthistle


Invasive Species: Centaurea calcitrapa, Purple Starthistle

Purple starthistle is a biennial to perennial invasive plant. It grows 2 to 3 ft. (0.6 to 0.9 m) tall. The stems and leaves are covered with fine hairs. Lower and basal leaves are divided or deeply lobed. Leaves become less divided toward the apex of the plant. Flowering occurs from July to October, when purple to pink blooms develop at the ends of the stems. Floral bracts are tipped with 1 in. …

Carduus tenuiflorus, Slenderflower Thistle


Invasive Species: Carduus tenuiflorus, Slenderflower Thistle

Slenderflower thistle is an herbaceous winter annual or biennial plant that invades disturbed areas. The most serious infestations occur in the Pacific coastal states, but slenderflower thistle also occurs sporadically in the eastern United States. Plants grow up to 6 ft. (1.8 m) tall with single or multiple spiny stems with wings arising from the base of the spines. Stem wings can be up to 0.4 in. (10 mm) wide. Leaves are deeply …