GAINESVILLE, Fla. – If you’ve driven down two-lane highways in rural parts of North Florida recently, you may have noticed a spate of new signs that designate the grassy knolls bordering the asphalt as wildflower areas.
The signs likely feel redundant right about now as thousands of milkweeds produce thick umbels packed full of pentagonal buds and fully developed flowers.
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Many of these flowers and all the monarchs they attract have the same attention-grabbing orange color as the safety vests worn by workers who carefully planted each milkweed by hand months earlier.
“It’s been a lot of work but also really exciting to see,” said Jaret Daniels, curator of Lepidoptera at the Florida Museum of Natural History. “We’ve had good success with plant establishment, and we’ve seen monarchs using the plants already in the field.”
The work is part of an initiative led by the University of Illinois Chicago to transform the vacant rights-of-way alongside roads, powerlines and train tracks into environmental corridors for monarch butterflies and other pollinators.
The Florida Department of Transportation signed on to this voluntary initiative — given the lengthy name of candidate conservation agreement with assurances for the monarch butterfly — in 2024, agreeing to manage 10,200 acres of roadside real estate for conservation, in part, by adding a few pollinator pit stops in strategic locations.
Milkweed areas benefit pollinators and people
FDOT proactively awarded a $150,000 grant to the Daniels lab in 2023 to select, grow, plant and monitor 9,000 milkweeds along Florida roads for a period of three years to understand the most effective planting strategy for milkweed establishment.
The grant was recently extended through 2029 with the goal of getting an additional 6,000 plants in the ground.
“It’s a no-brainer,” Daniels said. “We don’t have enough conservation lands to maintain pollinator populations through time in many areas, so we have to look to environments that we, as humans, manage every day. Roadsides are managed regardless, so why not do so in a way that confers greater benefits?”
The benefit to pollinators is obvious. Most of the crowd favorites in the insect world — bees, moths, butterflies — along with those of equal ecological importance but less esteem — wasps, flies, mosquitos, ants — subsist completely or partially on nectar.
A long stretch of country road straddled by wildflowers is a buffet for nectivores, and milkweeds are an excellent source of nectar for representatives from all of these groups.
Milkweeds are in the dogbane family of plants, Apocynaceae. Several species in this aptly named group produce toxic glycosides and alkaloids to discourage herbivory.
But as often happens in these cases, animals have consistently found ways of sidestepping the issue of imminent death following ingestion by developing physiological coping mechanisms.
In 2011, for example, scientists discovered that the world’s only poisonous rodent steals its toxin from a type of milkweed in East Africa, after which the toxin is administered to anything that tries to eat it through contact with the long quills on its back that give it the appearance of a porcupine.
Monarchs have pursued a similar idea by preventing the glycoside toxins present in milkweeds from binding to receptors in their bodies.
Rather than expelling the toxin, they store it in various tissues to deter predators.
Monarch larvae have gotten so good at doing this trick that they’ve lost the ability to eat anything that isn’t a milkweed. An environment characterized by the presence of milkweed is thus also a potential monarch nursery.
Milkweed corridors are of particular importance to adult monarchs as well, which have an insatiable sense of wanderlust. Individuals can travel more than 100 miles in a single day. That kind of long-haul trekking requires ample energy reserves, which monarchs get by making frequent stops at household gardens, natural areas and overgrown abandoned lots to refuel on nectar.
But the dividends of wildflower corridors pay out to more than just pollinators.
Birds and other predators get a piece of the pie, and lands adjoining the roads get the benefit of pollinator spillover.
Suitable locations of each roadside milkweed area were assessed years in advance to maximize these benefits as part of a separately funded initiative.
“We had done a one-year project where we mapped native milkweed populations along roadsides, so we had that as a starting point,” Daniels said. “By partnering with FDOT, we’re trying to fill in gaps where we know appropriate habitat occurs, but there are limited or no milkweeds that grow there.”
Many of the suitable spots are directly adjacent to conservation areas, where the extra pollinators will help augment and strengthen pre-existing biodiversity.
Others are near farmlands with crops like blueberries and watermelons that get a boost from wild insect pollination. Plus, a mosaicked landscape buzzing with insect activity is also just a lot of fun to look at.
Florida is a test case for future milkweed corridors
The six-year project is also an experiment to see what does and doesn’t work. Daniels and his team are currently focused on planting and monitoring milkweeds in Alachua and five other North Florida counties.
What they learn there will later be used to expand the initiative to other counties and states.
There are several variables being evaluated before that happens, including the type of milkweed that stands the best chance of surviving in these unique environments.
From an initial pool of six native milkweed species, Daniels has focused on pinewoods milkweed (Asclepius humistrata) and butterfly weed (Asclepius tuberosa), which have a proven track record of supporting monarch populations and thriving in conditions that many other plants struggle with.
“Both are upland, sand-loving species that would normally be found in pinelands and sandhills,” Daniels said.
Their preference for dry, poorly developed soils gives them an edge when it comes to growing on unsheltered mounds with little to no nutrient input, but it also makes logistics more challenging.
Butterfly weed is grown and sold commercially, but the pineland species has a taproot that requires special elongated pots for propagation. That, along with its preference for the types of poor soils that aren’t generally a hallmark of a well-tended garden, has prevented their entry into the horticultural market.
To get around that problem, Daniels’ team created their own milkweed supply chain. They start by collecting seeds from a few sites where they know pinewoods milkweed is common.
This involves traveling to each site multiple times a month during the plant’s flowering season to tie small bags around developing seed pods. This ensures the seeds don’t unfurl their silky mop of cellulose fibers and fly off in a gust of wind before they can be harvested.
Next, the seeds are transported to the University of Florida Native Plant Nursery, where staff and volunteers perform the understated miracle of guiding a picky plant from embryonic stasis through reproductive maturity.
“The last batch of seed we gave them had about a 98% germination rate, and we’ve seen really good establishment of these plants in the field,” Daniels said. “The Native Plant Nursery has been an invaluable partner in this project.”
They purchase butterfly weed from Green Isle Gardens in Groveland, Florida. Then comes the hard work of landscaping.
“We plant them when they’re dormant during the winter months, which is great for us and the young plants, because neither of us has to deal with the extreme heat of summer.”
Finally, the team regularly monitors the plants and does all the downstream number crunching that will ultimately tell them whether their efforts were a success worth replicating elsewhere.
It’ll be a few years before they reach a final verdict, but you can judge the results for yourself the next time you drive through an official Florida milkweed area.