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 …

Najas minor, Brittleleaf Naiad


Invasive Species: Najas minor, Brittleleaf Naiad

Brittleleaf naiad is an invasive annual forb that is native to Europe. The highly branched stems can grow up to 4 ft. (1.2 m) in length and fragment easily; hence the common name. Leaves are opposite, linear, and approximately 1 in. (2.5 cm) in length with prominent teeth along the margins. Flowering occurs in late spring to early summer, when small flowers develop in the axils of the leaves. Fruit are single-seeded. Germination …

Myriophyllum heterophyllum, Variable Watermilfoil


Invasive Species: Myriophyllum heterophyllum, Variable Watermilfoil

Variable watermilfoil is an invasive perennial aquatic herb that has leaves of two noticeably different forms. The submerged leaves are finely dissected, whorled, reddish/greenish-brown, and 1/2 to 2 1/2 in. (1.3 to 6.4 cm) long. The emergent leaves are small, oval, bright green, whorled, and up to 1/4 in. (0.6 cm) wide. Emergent leaves stand 6 to 8 in. (15.2 to 20.3 cm) out of the water and may not be apparent until …

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. …