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Plant of the Week
Morden Pink Loosestrife
Latin: Lythrum virgatum
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
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