Perennial or woody half-shrub.
Purple loosestrife is a shrub-like plant with stiff, four-sided
stems ending in spikes of showy purple flowers. Short, narrow leaves are
stalkless. Plants become taller and bushier over the years as the rootstock
matures, growing to 3 m in height.
Purple loosestrife is an ornamental which has escaped and now occupies
wetlands, stream banks, and shallow ponds. It can form dense stands that
reduce plant and animal diversity in wetland ecosystems.
Purple loosestrife is found in wet areas at low to mid-elevation
in BC, where it grows in ditches, irrigation canals, marshes, stream and
lake shorelines, and wetlands. It can tolerate a wide range of conditions
and will even grow in standing water. It is common in the Lower Fraser
Valley and frequent on southern Vancouver Island and in the Okanagan.
There are also localized patches in the Kootenay and Omineca regions.
Seeds are mainly distributed by water, but they can also be dispersed
by animals and humans. Seeds do not drop until the air temperature becomes
cold in the early autumn. A single plant can produce over 300,000 seeds.