Purple Loosestrife, Lythrum salicaria , Plants of the Eloise Butler Wildflower Garden

	Plants of the Eloise Butler Wildflower Garden
	Common Name	Scientific Name	Plant Family	Garden Location	Prime Season
	Purple Loosestrife	Lythrum salicaria L.	Loosestrife (Lythraceae)	Woodland	Early to Late Summer
Other names and notes	This erect perennial grows 3 to 7 feet in height and occupies the aquatic edges of streams, lakes, swamps, etc. Main stems have 4 or more angles and the stem secures itself with dense woody roots. The purple to reddish flowers are 1/2 to 1" wide and occur on terminal spikes that can be up to 16" high. Flowers are 6-part and have a wrinkled appearance. The leaves are 1 1/2" to 4" long, lance like, downy, smooth edges, and stalkless. They are opposite but can have whorls of 3. The plant is exceedingly invasive. Each plant can produce up to 2.7 million tiny seeds which are viable for years.


Above Left: Typical branching at the top of a main stem. Center: Tubular flower detail. Right: Stalkless opposite leaves.

Below - Historical Photo: Birch Pond, located just outside the Garden, shown surrounded by stands of Purple Loosestrife on August 5, 1950. The Garden is located up the hill behind the trees. Biological means were used in the early 2000's to eradicate it. Note the white swan in the pond. Photo from a Kodachrome by Martha Crone, courtesy Minnesota Historical Society, Martha Crone Collection.

Notes: Originally introduced from Europe as a garden perennial, it has invaded and spread across the United States and southern Canada. Only Arizona and a few gulf coast states seem to have escaped it. In Minnesota it is found in a number of counties, principally in the eastern half of the state. Noxious: In Minnesota it is listed as a "Prohibited noxious weed" which precludes it's sale by any nursery. In recent decades it has been the successful target of extirpation by biological means, using a particular beetle that feeds on the plant and gradually weakens it so it cannot produce seed. The Minneapolis Park and Recreation Board has successfully used this method to remove the plant from nearby Birch Pond. In the Garden it is under strict control. It has been present in the Garden for a long time; Martha Crone listed it on her 1951 Garden Census.

As noted above, it was not originally apparent how invasive the plant would be. Planting was still advocated into the 1960's. Former Curator Martha Crone did so, but also acknowledged the invasive tendency in this comment: "It is a good plant to grow along streams, margins of ponds or in wet meadows. Especially where the competition is too severe for less aggressive plants to grow. The Plant is a long-lived perennial and produces graceful spikes of purple or pink flowers. They bloom during July and August. When once established it is hard to eradicate and will crowd out other weaker growing plants. It can be grown in garden borders where it remains smaller and does not spread. This six-petaled flower has 12 stamens of two different lengths, and the length of the single pistil varies in different flowers; this is termed by botanists as trimorphous. Only pollen from stamens of the same length can pollinate stigmas, therefore each flower is sterile to its own pollen, thus ensuring the vigor of the race." Published in the Fringed Gentian ™ April 1958, Vol. 6 #2

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References: Plant characteristics are generally from sources 15, 16, 30, 31, 33, W2 & W3. Distribution principally from W2 and also 31, 34 and W1. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.

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