Purple loosestrife may rise two metres in height and 1.5 metres in width with up to 50 erect stalks to a single woody root mass. The wide, downy and sessile leaves are 3-10 centimetres in length and opposite in two ranks. Although easily identified during its blooming season from June to September, purple loosestrife may be distinguished from similar native plants (i.e. fireweed, Epilobium angustifolium; blue vervain, Verbena hastata; blazing stars, Liatris spp. and spirea, Spiraea douglasii) by its angular stalks which are square in outline.
A single plant may produce up to three million tiny seeds annually. Easily carried by wind and water, the seeds germinate in moist soils after over wintering. Once established, infestations are extremely difficult and costly to remove by mechanical and chemical means. An alternative has been sought in biological pest control; the release of insects into North America known to feed exclusively on purple loosestrife has met with considerable success. Use of the four insect species – two beetles (Galerucella calmariensis and G. pusilla) and two weevils (Hylobius transversovittatus and Nanophyes marmoratus) provides an effective alternative to harmful herbicides in sensitive ecosystems."
