Sterile cultivars of loosestrife may not be so
The showy purple spikes of purple loosestrife (Lythrum salicaria and L. virgatum) are attractive both in the garden and on roadsides. But their rampant spread has greatly reduced the ecological value of marshes by displacing native wetland vegetation such as cattails (Typha spp.) that waterfowl feed on and that muskrats and long-billed marsh wrens need to build their nests. And these are only a few examples of the damage that invasive plants inflict on our native landscape.
Reportedly sterile cultivars (those that do not produce viable seed) of purple loosestrife are being sold at nursery centers across the nation. However, Bernd Blossey, the director of the Biological Control of Non-Indigenous Plant Program at Cornell University explains that this claim is not valid. “Unfortunately, the claim that cultivars of purple loosestrife are sterile is totally false. Research has shown that if cultivars such as ‘Morden Pink’, ‘Morden Gleam’, and ‘Dropmore Purple’ are grown with other cultivars or wild loosestrife, the seeds are highly fertile, with more than a 90-percent germination rate. Bees carry its pollen far and wide. To label these plants as sterile and not a threat to the environment is misleading and irresponsible behavior on the part of those selling the plant.”
The fact that some gardeners have begun to think that they can grow this plant with a clear conscience has helped it stage a comeback of sorts. Blossey adds, “One mature plant can produce over 2 million seeds annually that are easily transported by the wind or water into wetlands. The seeds germinate without any special treatment, and no natural predator holds this plant in check.”