Lythrum salicaria Purple-loosestrife

An attractive, tall, perennial herb with opposite or whorled leaves, which produces spires of purple flowers in summer. It is found in wet places often in the emergent margins of slow-flowing aquatic habitats such as lakes, ponds and canals and also in fens, marshes, wet woodland and other habitats that are periodically flooded and nutrient enriched. The flowers, which have 6 petals and 12 stamens, are arranged in whorls and their complex, trimorphic, heterostylic structure was described by Charles Darwin in The Different Forms of Flowers on the Same Plant (1877);  the styles and stamens are of 3 lengths, some long, some medium-length and some short. The pollen grains are also of 3 sizes with the largest grains associated with the longest stamens. The proportion of the 3 floral structures in a population varies from site to site. It is widespread and common in much of Britain and Ireland but absent from parts of the north. It is found throughout West Glamorgan, but is largely absent from the uplands. Outside its native range, particularly in North America where it has been nicknamed 'the purple peril', it has become a serious invasive weed in some wetland habitats.

Native