Lythrum salicaria L. (Purple loosestrife )

 


Bruso, George H.,
Native Plant Information Network

 

 

 

Family: Lythraceae (Loosestrife Family)

Synonym(s): Lythrum salicaria var. gracilior, Lythrum salicaria var. tomentosum, Lythrum salicaria var. vulgare

Duration: Perennial

Habit: Herb


Listed by:
Invasive Plant Atlas of the US: 1
Federal Noxious Weed: 0
TDA Noxious Weed: 1
TPWD Prohibited Exotic Species: 1

Description: Leafy, angular stems have crowded spikes of brilliant pinkish-lavender flowers at top, opposite or whorled, unstalked leaves below. Plant grows in dense patches. Flowers: 1/2-3/4" (1.3-2 cm) wide; petals 4-6, nearly 1/2" (1.3 cm) long, attached to a purplish calyx-like tube with several pointed teeth; stamens as many or twice as many as petals; flowers of 3 types, each with different stamen and pistil lengths. Leaves: 1 1/4-4" (3.1-10 cm) long, narrow, opposite, notched at base; lower ones downy, clasping the stem. Height: 2-7' (60-210 cm).

History: Lythrum salicaria derived it?s name from a Greek medical man in Nero?s Roman army when he called the plant Lytron, Greek for blood. Awareness of the medicinal properties or the flowering spike resemblance to blood or gore from a wound led to the name. The similarity of loosestrife leaves to those of the willow (Salix spp.) resulted in the species name of salicaria. (Balogh 1986). The first North American record of purple loosestrife was in wet Canadian meadows and in New England, as recorded in Pursh?s Flora Americae Septentrionalis, in 1814. (Louis-Marie 1944 as cited in Balogh 1986). It was first recorded as a problem weed in Quebec in the 1930?s. By 1942, a pasture that at one time supported 800 head of cattle was declared useless. (Balogh 1986).

Biology & Spread: Purple loosestrife enjoys an extended flowering season, generally from June to September, which allows it to produce vast quantities of seed. The flowers require pollination by insects, for which it supplies an abundant source of nectar. A mature plant may have as many as thirty flowering stems capable of producing an estimated two to three million, minute seeds per year.

Purple loosestrife also readily reproduces vegetatively through underground stems at a rate of about one foot per year. Many new stems may emerge vegetatively from a single rootstock of the previous year. "Guaranteed sterile" cultivars of purple loosestrife are actually highly fertile and able to cross freely with purple loosestrife and with other native Lythrum species. Therefore, outside of its native range, purple loosestrife of any form should be avoided.

Ecological Threat: Purple loosestrife adapts readily to natural and disturbed wetlands. As it establishes and expands, it outcompetes and replaces native grasses, sedges, and other flowering plants that provide a higher quality source of nutrition for wildlife. The highly invasive nature of purple loosestrife allows it to form dense, homogeneous stands that restrict native wetland plant species, including some federally endangered orchids, and reduce habitat for waterfowl.

US Habitat: Purple loosestrife occurs in freshwater and brackish wetlands. It is a successful colonizer and potential invader of any wet, disturbed sites in North America. Associated species include cattails, rushes, sedges, and reeds.

Distribution

US Nativity: Introduced to U.S.

Native Origin: Europe (NatureServe Explorer); Old World (Bailey, L.H. and E.Z. Bailey, Hortus Third: A Concise Dictionary of Plants Cultivated in the United States and Canada, MacMillan Publishing Co., Inc., New York , (1977).)

US States: AL, AR, CA, CO, CT, DE, IA, ID, IL, IN, KS, KY, MA, MD, ME, MI, MN, MO, MS, MT, NC, ND, NE, NH, NJ, NV, NY, OH, OK, OR, PA, RI, SD, TN, TX, UT, VA, VT, WA, WI, WV, WY

Resembles/Alternatives: Native species of Liatris (blazing star) have showy pink-purple flower spikes and are an important nectar source for many native species of butterflies and other insects. Other alternatives include: Joe Pye weed (Eupatorium fistulosum), cardinal flower (Lobelia cardinalis), blue vervain (Verbena hastata), blazing star or gayfeather (Liatris spicata), New York ironweed (Vernonia noveboracensis), obedient plant (Physostegia virginiana).

Management: Purple loosestrife also spreads vegetatively. Buried stems harbor adventitious buds with the ability to produce shoots or roots. Disturbance to the plant, such as stomping and breaking underground stems, or breaking off stems or roots during incomplete plant removal, does initiate bud growth. Cutting alone is not a control option for purple loosestrife. Shoots and adventitious roots will develop. Cutting late in the season reduced shoot production more than mid summer cutting, indicating that carbohydrate reserves could not be restored for next years growth.

USE PESTICIDES WISELY: ALWAYS READ THE ENTIRE PESTICIDE LABEL CAREFULLY, FOLLOW ALL MIXING AND APPLICATION INSTRUCTIONS AND WEAR ALL RECOMMENDED PERSONAL PROTECTIVE GEAR AND CLOTHING. CONTACT YOUR STATE DEPARTMENT OF AGRICULTURE FOR ANY ADDITIONAL PESTICIDE USE REQUIREMENTS, RESTRICTIONS OR RECOMMENDATIONS. MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.

Listing Source

Texas Department ofAgriculture Noxious Plant List
Texas Parks and Wildlife Department Prohibited Exotic Species
Invaders Program
Federal Noxious Weed
Union of Concerned Scientists
United States Forest Service Southern Research Station

Text References

Balogh, G. 1986. Ecology, Distribution and Control of Purple Loosestrife (Lythrum salicaria) in Northwest Ohio. Thesis for Master of Science Degree from Ohio State University. 107 pp.

Data Source

APWG WeedUS Database

Swearingen, J., K. Reshetiloff, B. Slattery, and S. Zwicker. 2002. Plant Invaders of Mid-Atlantic Natural Areas. National Park Service and U.S. Fish & Wildlife Service, 82 pp.

Last Updated: 2007-08-10 by EEE