There are only three British Isles species in the lythraceae, or loosestrife family; lythrum salicaria, lythrum hyssopifolia and lythrum portula. Plants in this family have whorled or opposite leaves, crossed by pinnate veins, and flowers with varying number of petals and sepals; six for the UK species, though four for most others. There are usually twice as many stamens as petals.