Family: Lythraceae, Loosestrife view all from this family
Description Despite its highly invasive nature, this erect, semi-aquatic weed of wet ground and standing water bears pretty purple flower spikes.
Habit: introduced perennial subshrub or herb; angled, gray, finely hairy stems from woody roots; colony-forming.
Height: 1-7 ft (0.3-2.1 m).
Leaf: opposite or 3-whorled (rarely alternate above), lanceolate, stalkless, often finely hairy, 1.25-5.5 in (3-14 cm) long.
Flower: wrinkled 4-7-pointed star, lavender-pink, magenta-veined, 0.5-1 in (1-2.5 cm) wide, from toothed, purple-red tube 0.2 in (5 mm) long; stamens of 3 different lengths; in crowded to interrupted terminal spike 4-16 in (10-40 cm) tall.
Fruit: cylindrical capsule, 0.125 in (3 mm) long.
Flower June to September.
Habitat Open, wet sites: wet meadows, shorelines, standing water.
Range Native to Eurasia; introduced and naturalized throughout North America, except for the far north, Arizona, Louisiana, Florida, Georgia and South Carolina.
Discussion Also called purple lythrum, rainbow weed, salicaire, spiked loosestrife, bouquet violet. An obligate wetland indicator.Considered invasive and weedy in nearly all areas; banned or noxious wherever it occurs.
Infestations result in dramatic disruption in water flow in rivers and canals, and a sharp decline in biological diversity as native food and cover plant species, notably cattails, are completely crowded out, and the life cycles of organisms from waterfowl to amphibians to algae are affected. 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 overwintering. The plant can also sprout anew from pieces of root left in the soil or water. Once established, loosestrife stands are difficult and costly to remove by mechanical and chemical means.