Purple Loosestrife

Purple loosestrife in bloom.DESCRIPTION

Purple loosestrife is an erect perennial herb in the loosestrife family, with a square, woody stem and opposite or whorled leaves. Leaves are lance-shaped, stalkless, and heart-shaped or rounded at the base. Plants are usually covered by a downy pubescence. Loosestrife plants grow from four to ten feet high, depending upon conditions, and produce a showy display of magenta-colored flower spikes throughout much of the summer. Flowers have five to seven petals. Mature plants can have from 30 to 50 stems arising from a single rootstock. 


Purple loosestrife adapts readily to natural and disturbed wetlands. As it establishes and expands, it outcompetes and replaces native grasses, sedges, and other flowering plants that provide a higher quality source of nutrition for wildlife. The highly invasive nature of purple loosestrife allows it to form dense, homogeneous stands that restrict native wetland plant species, including some federally endangered orchids, and reduce habitat for waterfowl.



Purple loosestrife monoculture in a wetland.

How You Can Help:

Purple loosestrife has been spreading in the marshes of the mid-Patuxent for the past several years. Removal efforts have included mechanical (digging out the plants, cutting flowers), biological (placing herbivorous beetles on the plants), and herbicide treatments began in 2011 in conjunction with cuttings.

Volunteers can be of great assistance in summer when plants are flowering. Staff scheduled work days give participants a chance to travel by boat to wetland sites where the plants occur. Bagging and disposing of flower/seed heads can help reduce the spread of this NNI.

Western Branch 2010 purple loostrife infestation areas.

Western Branch tributary purple loosestrife infestation areas.

Main site of purple loostrife infestation, 2010.

Main site of Western Branch purple loosestrife infestation.