Lythrum plants are hardy perennials. They can reach an height of 150 cm (5 feet).
Be aware that they are an invasive species in many areas in Northern America, and growing them is banned in the garden in many areas.
This is to help with control of these plants in native wetland areas.
Lythrum salicaria by Ettore Balocchi.
In areas where it can be grown non-invasively, it makes a useful pond edge plant. When in bloom it carries purple-red flowers.
Lythrum alatum - Winged Loosestrife by bob in swamp.
Lythrum alatum (Winged Loosestrife), photograph by Frank Mayfield; CC.
Lythrum hyssopifolia (Hyssop Loosestrife / Grass-poly), photograph by Doug Beckers; CC.
Lythrum salicaria (Purple Loosestrife / Spiked Loosestrife), picture by Andreas Rockstein; CC.
Common Names: Loosestrife, Purple Loosetrife, Purple Willow Herb, False grass-poly, Red Sally.
Life Cycle: Hardy perennial.
Height: 24 to 60 inches (60 to 150 cm).
Native: Asia. Australasia. Africa. Europe.
Growing Region: Zones 3 to 9.
The Gardener's HQ Guide to Growing and controlling Lythrum Plants
I hope that you found this guide on how to identify Lythrum plants useful. You may also enjoy my gardening guides on how to grow Gloriosa-lily, Asclepias syriaca and Lima Bean plants.