Buyer Beware
“Non-invasive” ornamental plants probably aren’t
The Japanese barberry is a pretty little bush – thorny, yes, but the bright red berries can brighten up a winter garden. But the barberry has a dark side: Many U.S. states and Canada now ban the plant’s sale because of its prowess as an invader. To sidestep such rules, some nurseries now tout certain varieties of barberry and other banned plants as “less invasive.” But that label probably won’t stand up to scientific scrutiny, a new study warns.
“We are concerned that the marketing of cultivars as ‘safe to natural areas’ has advanced much faster than the research evaluating those cultivars,” Tiffany M. Knight of Washington University in St. Louis, Missouri, and Kayri Havens and Pati Vitt of the Chicago Botanic Garden in Glencoe, Illinois write in BioScience. Although these “safer” plants typically produce less seed than their more fecund relatives, “the critical question then becomes how much of a reduction in seed production or seed viability is necessary to create a cultivar that will not be invasive.” And so far, they say, few studies have tried to answer that question.
To sow their own seeds for discussion, the researchers combed the scientific literature for studies that examined the population dynamics of 19 invasive plant species from 13 different families. Using population models, they revealed a worrying trend: Even long-lived plants that produce 95 percent fewer seeds than usual are quite capable of spreading — and many of the new cultivars do not achieve even that much of a seed reduction. “Large reductions in fecundity are inadequate to reduce population growth, particularly for invasive woody plants,” they conclude.
The researchers also note that nursery plants often do not “breed true,” meaning that the offspring can produce more seed than the parents, especially when domesticated plants cross with feral varieties that have already escaped into the wild.
“Marketing less fecund cultivars as ‘safe’ is premature at this time,” they conclude, adding that such labels should be “based on evaluations that consider the entire life cycle of the cultivar and its offspring.” The only truly safe plants, they add, are “female sterile cultivars that cannot reproduce asexually.” Researchers have figured out how to use genetic engineering techniques to produce “supersterile” crop plants that are unable to reproduce, they note, but haven’t yet applied them to “horticultural shrubs.” – David Malakoff | October 10, 2011
Source:Tiffany M. Knight, Kayri Havens, and Pati Vitt. Will the Use of Less Fecund Cultivars Reduce the Invasiveness of Perennial Plants? BioScience • October 2011 / Vol. 61 No. 10 www.biosciencemag.org
Image © Milkakotka | Dreamstime.com
Interesting article…It is important to be aware of the plant and animal species we are importing! It is much easier to prevent an ecological invader than to remove one once it is “rooted” in.