Drought may be triggering loosestrife boom

SUDBURY, Mass. — It's been part of the late summer landscape in Massachusetts since the early 1800s. But in recent years, purple loosestrife seemed harder to come by, thanks to a biocontrol project that kept the invasive plant at bay. 

But in some communities this summer, purple loosestrife is making a comeback.

"I remember seeing some of it here and there, but it's really gone bonkers this year," said Linda Chiarizio, co-owner of Tangerini's Farm in Millis, where a field adjacent to the kale is awash in purple-pink. "I don't think I've ever seen so much of it." 

The flowering spires of purple loosestrife are beautiful, admitted Georgeanne Keer, a project manager at the state Division of Ecological Restoration; but it comes with a high price.

“This plant can push out and dominate a system,” Keer said. “You have this plant that has the potential to just take over and sort of really drastically change that system.”

Purple loosestrife dominates native plants because it can reproduce faster and in higher quantity -- and because it has no native predators. 

"The plant itself produces millions of seeds," Keer said. "This plant can also establish itself in other areas from stem cuttings."

Purple loosestrife likely came to the United States in the ballast of a ship from Europe or Asia. To control it, researchers imported a beetle about 30 years ago from that region which feeds exclusively on the plant.

“The stems, the flowers, the leaves -- they eat all parts of the plant,” Keer said. 

From 2001 to 2008, Massachusetts released beetles as a biocontrol for purple loosestrife and it seemed effective at diminishing the population. Keer explained that the beetles go through two life cycles in rapid succession in spring and summer, the second emergents going dormant in winter and re-emerging as perpetuants in spring. 

But currently, the state is not engaged in such efforts. 

"We do provide some technical assistance, answering some questions about the history of the program and other available resources,"  Keer said. "But it is not a primary activity that we're engaged in."  

In a Sudbury wetland, Frederick Sechler, Jr., an ecologist with the Native Plant Trust, points out evidence of beetle damage on a purple loosestrife plant. 

“Pretty typical ring holes,” Sechler said. “The beetles have been eating some of the leaves on the stem.” 

The presence of those beetles may be why purple loosestrife hasn't come to dominate this area of wetlands. It contains more typical New England plants: Joe Pye Weed and Goldenrod. 

"The plants in these native wetlands in the Northeast haven't really evolved the capacity to compete with purple loosestrife over time," Sechler said. "This may change." 

If it does -- if evolution gives native plants the ability to keep purple loosestrife in check -- Sechler foresees a time when it might not be labelled a 'noxious weed.'

"It may just become part of the landscape of the wetlands. It may not be a problem."

But for now, it is a problem. And Sechler thinks the reason purple loosestrife proliferated this summer has a lot to do with the weather -- specifically, the drought. 

"It's definitely favorable conditions this year, I think, for purple loosestrife to thrive more," he said. 

Keer agrees this is possible. But wonders if first the wetlands got flooded, killing off the biocontrol beetles.

“These beetles are very susceptible to flooding,” Keer said. “They’re not very hardy.”

If the drought that followed exposed open ground, that would be an ideal situation for purple loosestrife to get established, according to Keer.  

"Many invasives are really good at finding that niche and you know taking advantage of the available resources," Keer said. "That is one very well known mechanism for plants to become established and start their population explosion." 

If that’s what happened -- and the beetle-count is down -- the question for the future is... will the purple loosestrife count keep going up?

Cox Media Group