The Collaborative International Dictionary
Lythrum Salicaria
Willow-herb \Wil"low-herb`\, n. (Bot.) A perennial herb ( Epilobium spicatum) with narrow willowlike leaves and showy rose-purple flowers. The name is sometimes made to include other species of the same genus.
Spiked willow-herb, a perennial herb ( Lythrum Salicaria) with willowy leaves and spiked purplish flowers.
Wikipedia
Lythrum salicaria
Lythrum salicaria (purple loosestrife) is a flowering plant belonging to the family Lythraceae. It should not be confused with other plants sharing the name loosestrife that are members of the family Primulaceae. Other names include spiked loosestrife, or purple lythrum.