Plans are afoot to help increase local roadside ditches’ value as pollinator habitats.
Such ditches “are a potential gold mine for milkweed and other pollinator plants,” said Clark McLeod, director of the Cedar Rapids-based Monarch Research Project.
The group has joined forces with Linn County Integrated Roadside Vegetation Management to promote the development of citizen groups to plant milkweed and other pollinator habitat in Linn County road ditches.
The 80 percent decline in monarch butterfly populations during the past 20 years is attributable in large part to the loss of milkweed — the only plant on which monarchs lay their eggs and the only plant their larvae will eat.
McLeod said some existing Adopt-A-Road groups will add the nurturing of pollinator plants to their regular litter-gathering services. The county also will recruit additional groups to cover more of the available roadways, said Rob Roman, Linn County’s roadside vegetation manager.
“It’s a good thing, and we are excited about it,” Roman said.
The county’s Adopt-A-Road program, established in the early 1990s, always has had a vegetation component, Roman said, but the county has never promoted it.
The new program will be introduced July 22 at a celebration of Linn County’s 28 existing Adopt-A-Road groups.
Other groups wanting to participate or learn more are encouraged to attend the meeting from 1:30 to 3:30 p.m. at 4970 Lakeside Rd., Marion. (To RSVP, email to email@example.com.)
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McLeod said Linn County’s 1,140 miles of roadside ditches have the potential to grow an additional 1.4 million milkweed plants. That would be the county’s fair share of the additional milkweed stems needed in the Midwest to restore habitat to a level sufficient to foster a secure monarch butterfly population, McLeod said.
John Pleasants, an assistant biology professor at Iowa State University, said his research shows it would take 1.6 billion additional milkweed stems in the Midwest to increase the monarch butterfly population to a sustainable level, which he defines as five times greater than the most recent overwintering populations in Mexico.
Given that Iowa has about nine percent of the Midwest’s milkweed-suitable land, its share of that goal, he said, is 137 million additional milkweed stems.
Little if any additional milkweed can be grown in the herbicide-treated farm fields that cover about two-thirds of the state. In fact, the widespread use of the herbicide glyphosate — most commonly applied as Monsanto’s Roundup — has eliminated about one billion milkweed plants from North American crop fields. That’s roughly half the milkweed available to the butterflies when their decline began 20 years ago, he said.
In Iowa, that leaves roadside ditches and Conservation Reserve Program grasslands as the biggest contributors, Pleasants said.
Roadsides, he said, “are the low-hanging fruit. Anyone can participate without seeking permission.”
Pleasants said ISU research has established that swamp milkweed is “a notch above” common milkweed in its attractiveness to monarch butterflies. But common milkweed is hardier and easier to establish, which accounts for its higher prevalence in roadside ditches and for his recommendation that it be planted by Adopt-A-Roadway groups.
Under the simplest planting option, groups would use garden rakes to scrape and clear thatch in a series of one-by-three-foot patches spaced at intervals in the ditch. Seed planted in late autumn in the bare soil would be expected to germinate the following spring.
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Under the micro prairies option, beginning next year, native seed will be planted in six-foot diameter circles clustered or spread linearly in the ditch.
The Monarch Research Project and the McLeod Foundation will raise money to buy seed mixes, supplies and equipment necessary to establish the plantings.