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Morden Pink Loosestrife

Plant of the Week

Morden Pink Loosestrife
Latin: Lythrum virgatum

Picture of Morden Pink Loosestrife with purple flower spikes.

Gardeners are, by and large, a honest set of folk. But deep down, a bit of larceny lurks in us all. Who amongst us has not pinched a cutting here or pocketed a seed capsule there?

Justification for such petty pilferage is easy to come by, and most of us feel it does no harm, but Big Brother does not always agree. State regulatory authorities at the Arkansas State Plant Board have banned two garden plants in recent years as noxious weeds. Like a small quantity of marijuana in California, it is not illegal to have the plant, but it is illegal to sell or transport it.

Morden Pink Loosestrife, a member of the loosestrife family to which crape myrtle belongs, is a semi-woody perennial that grows to four feet in height and has willow-like leaves two to four inches long. In midsummer it produces 1-inch wide pink flowers crowded onto an upright spike that’s 6-8 inches long.

Morden Pink, developed by Dr. Skinner at the Agricultural Research Station in Manitoba, Canada, has been marketed since 1937 as a male sterile sport that’s not supposed to set seed. Apparently, when grown in isolation by itself, it is seedless (if it really is the original strain); but when pollinated by other related species, it too will bear seed.

Both this species and the look-alike species purple loosestrife (L. saliciaria) are native to the Old World and have become established as waterway weeds in the northern states. In the late 1980's, the US Fish and Wildlife Service, aided by Ducks Unlimited, began a campaign to outlaw planting Lythrum and eradicate established stands.

In the cooler north country loosestrife has escaped cultivation and clogs waterways and out competes less aggressive native species. Its seeds are not eaten by any of the native wildlife species, thus reducing the food supply for wild fowl. In 1990, Arkansas, fearing that loosestrife would escape here, banned all Lythrum species as illegal for sale in the state.

How big a threat is loosestrife to our wild areas, and was banning all species of Lythrum a knee jerk reaction to a perceived problem? The tenor of the argument went primarily along the "better safe than sorry" line, and in the big picture that is probably the most prudent approach to take.

I grew a strain of L. salicaria in a dry site in Fayetteville in about 1980 and observed no reseeding in the field under typical dryland conditions. One of these plants made its way to my garden at home. That plant was ringed by a number of seedlings the following spring, but none of these seedlings survived in my rather dry garden. If the site had been more moist, they probably would have survived.

Even supposedly sterile strains such as Morden Pink present a problem because too often the plant being sold is not what it is supposed to be. This mixup in cultivars is a never-ending problem in the nursery trade. The causes of name-mixing are varied, but it often is due to a nurseryman guessing that the plant they have is the same as whatever plant is most common in the trade at that time. Often the guess is wrong and selections become endlessly confused.

As gardeners, we want to do our part to insure that the natural habitat is not overrun by an aggressive invader. Foregoing the ability to purchase loosestrife is a small price to pay if it prevents the spread of the next dandelion. While relatively few of our common weeds were introduced as ornamentals, it can and does happen, so prudence is probably the best approach.

By: Gerald Klingaman, retired
Extension Horticulturist - Ornamentals
Extension News - July 21, 2000


The University of Arkansas Division of Agriculture does not maintain lists of retail outlets where these plants can be purchased. Please check your local nursery or other retail outlets to ask about the availability of these plants for your growing area.