Goutweed (Aegopodium podagraria)
Goutweed is a herbaceous perennial plant native to Europe and northern Asia. It was first brought to North America during the early stages of European settlement as an ornamental garden plant and is a commonly used groundcover. Today it is a problematic invasive species that is commonly found in moist forests, ravine systems and along water courses.
Goutweed is a small plant that spreads primarily by an underground rhizome. Mature plants can tolerate full sun to partial shade and a variety of moisture conditions. Its leaves are basal, and are divided into three groups of three leaflets. The leaflets are toothed and sometimes irregularly lobed or divided. The natural plant is a light green colour, but the variegated form with bluish green leaves with white edges is more commonly sold in garden centres.
Goutweed blooms between May and June, producing tiny white flowers arranged in flat topped clusters called compound umbels, which are held above the foliage on leafy stems (they look similar to Queen Ann’s lace). The seeds produced require recently disturbed soil and a sunny location to survive after germination. For this reason, goutweed does not have much success reproducing by seed in forest ecosystems. However, even one established plant can create a large colony by the spreading of its aggressive rhizomes.
As an invasive species, goutweed forms dense patches that displace native plants in the ground layer of an ecosystem. The primary cause of its spread over long distances is human activity in the form of intentional plantings and the dumping of yard waste containing goutweed plant parts.
Because it has limited reproductive success by seed, small patches of goutweed can be easily controlled by digging up the plant (with careful attention given to removing the entire rhizome) or covering with a tarp or weed barrier for at least one growing season. Plants dug up with intact rhizomes should be dried in the sun for several days to ensure they are dead and will not be able to resprout if they come in contact with a suitable substrate. Therefore if you are removing goutweed from your garden, do not put it in your compost.