Willowherbs, purple loosestrifes & allies

Lowland Rotala Purple Loosestrife Crape-myrtle Swamp Loosestrife

What are they?

This group of plants pulls together the pink-flowered members of the evening-primrose family and the members of the Purple Loosestrife family. This is a very variable bunch, ranging from creeping ground-huggers to large shrubby species.

Where are they found?

Most species can typically be found in damp or swampy ground, especially in rich soils.


Being variable in general appearance, members of this group are relatively easy to tell from one another by using the photos below.

Lowland Rotala      Rotala ramosior

An easily-missed, low-growing species with very small, pale pinkish flowers which can be common on bare ground in wetlands and other swampy areas. Flowers July to September.
Lowland Rotala Lowland Rotala Lowland Rotala Lowland Rotala
Tiny flowers
seed pods

Swamp Loosestrife      Decodon verticillatus

Common and widespread in all sorts of wetland habitats, where it can sometimes form quite extensive, shrubby stands. Flowers August to September.
Swamp Loosestrife Swamp Loosestrife Swamp Loosestrife Swamp Loosestrife
Flowers clustered
in leaf axils
Close-up of flowers
Leaves shiny
with pale midrib
Seed pods

Narrow-leaved Loosestrife      Lythrum lineare

An uncommon plant of brackish and saltwater marshes. Flowers July to early September. Flowers are very pale purple but often appear white.
Narrow-leaved Loosestrife Narrow-leaved Loosestrife Narrow-leaved Loosestrife Narrow-leaved Loosestrife
Flower close-up
Seed capsules

Purple Loosestrife      Lythrum salicaria

A seriously invasive alien, native to Europe. This species has caused major ecological damage to many wetlands in North America and should be removed on sight at an early stage before it gets a hold. The species spreads easily in wetlands and soon forms extensive, single-species colonies, to the exclusion of many native species. Despite this, the plant continues to be grown widely in gardens, though some more recent clones offered for sale are said to be sterile. Flowers June to September.
Purple Loosestrife Purple Loosestrife Purple Loosestrife Purple Loosestrife
Flowers in
long spikes
Close-up of flower
Leaves with
prominent veins

Crape-myrtle      Lagerstroemia indica

An extremely popular large shrub or small tree which is widely planted in gardens throughout the area. Though it provides a certain amount of nesting habitat for birds, this species is native to Asia and has little or no wildlife value in North America. Flowers throughout the warmer summer months. This species is included here as it is very showy and often catches the eye of people looking at plants in the region.
Crape-myrtle Crape-myrtle Crape-myrtle
Flowers typically
vivid carmine
Flowers may be
white or pale pink
Leaves shiny and rigid
Crape-myrtle Crape-myrtle Crape-myrtle
Seed capsules remain
through winter
Winter twig