How did Purple Loosestrife get to North America?
I often get asked when I speak to landowners about invasive species on their property, “How did it get here?” The response is usually one of four things:
- People brought it in because they wanted it around, usually for ornamental purposes (e.g. purple loosestrife, Japanese knotweed, hydrilla, European starlings, European privet)
- It was brought here to be eaten (e.g. garlic mustard, asian carp)
- It was endorsed for some form of erosion control or other human benefit (natural fencing, wildlife food source) and was not recognized as invasive at the time (e.g. kudzu, multiflora rose, cane toad, autumn olive).
- It arrived accidentally, either in an import or on the transportation moving the imports (e.g. zebra mussel, Japanese stiltgrass, Hemlock Wooly Adelgid, and purple loosestrife again [arrived in ships using soil for ballast])
Purple loosestrife falls into the first and the fourth category; it is not uncommon for invasive species to arrive a few different times in a new area, nor for invasive species to arrive in a few different ways.
Purple Loosestrife was primarily brought into the United States as early as the 1800s as an ornamental plant. Its tall purple spires were (and still are by some) considered very attractive, but its tendency to fill in entire wetlands has resulted in its classification as an invasive species.
Purple loosestrife has an enormous native range throughout Eurasia (throughout Great Britain, and across central and southern Europe to central Russia, Japan, Manchuria China, southeast Asia and northern India), but is kept in check in its native range by herbivores, disease, climate and the competitive ability of other native plants. Plants, insects, animals and diseases co-evolved with purple loosestrife in its native range, and so purple loosestrife is not disruptive in its native range. It can be a source of food and shelter, being kept in check by other members of the ecosystems it inhabits.
There are several attractive alternatives to purple loosestrife for landscaping, all of which are non-invasive and have the added bonus of providing good food sources for local pollinators. They include:
Water Speedwell (Veronica anagallis)
Marsh blazing star/Dense blazing star/Dense Gayfeather (Liatris spicata)
Prairie blazing star (Liatris pycnostachya)
Dotted gayfeather/Dotted Blazing Star (Liatris punctata)
Wild bergamont (Monarda fistulosa)
Joe-pye weed (Eupatorium maculatum)
Purple coneflower (Echinacea purpurea)
Queen-of-the-prairie (Filipendula rubra)
Black cohosh (Cimicifuga racemosa, Actaea racemosa)
Cardinal Flower (Lobelia cardinalis)
American Germander (Teucrium canadense)
Blue vervain (Verbena hastata)
There is also a good list of recommended native plants listed by State from the Lady Bird Johnson Widlflower Center: http://www.wildflower.org/collections/collection.php?collection=WV This list can allow you to landscape responsibly, using plants that are best adapted to your area and its native animals and plants.
PCA Alien Plant Working Group: Purple Loosestrife
Invasive Species Definition Clarification and Guidance White Paper
National Invasive Species Council, ISAC
Lady Bird Johnson Wildflower Center