What does it look like?
Purple loosestrife (Lythrum salicaria) is a herbaceous wetland perennial that reproduces and spreads mainly by seeds, but will also spread by pieces of stem or root. It has pink-purple flowers attached to the stem in a dense spike. The plant is tall (1-2 metres) with usually square stems. The leaves are smooth, tongue-like and are attached to the stem in an opposite to a spiral arrangement. One mature plant can produce up to 2.5 million seeds annually.
Its weedy nature…
Purple loosestrife was introduced into North America from Europe in the early 1800’s. It invades native wetlands and gradually takes them over choking out all native vegetation creating a dense purple landscape almost devoid of wildlife. The plant is a very prolific seed producer. The seeds can be spread by water, across snow or ice and may remain dormant for many years before germinating.
Pasture, lawn or other non-crop control
The plant should be dug out removing the complete plant including the roots. The plants can regrow from small pieces of root left behind. Place the plants in black garbage bags prior to disposal. Do not compost the plants. Ornamental lythrum or purple loosestrife growing in an ornamental location should also be removed and disposed using the same procedure.
Research has shown that wild purple loosestrife and ornamental lythrum can cross-pollinate, producing viable seed. As a result ornamental lythrum should be removed from our gardens and destroyed. If the plant isn’t removed the flower stalks should be removed before seed production and destroyed to prevent the spread of this invasive plant.
Photographic credits to Alberta Agriculture, Food and Rural Development, the British Columbia, Ministry of Agriculture, Food and Fisheries, Field Guide to Noxious and Other Selected Weeds of British Columbia and Strathcona County, Transportation and Agriculture Services.