Tropical Milkweed is a popular ornamental plant featuring bright orange and yellow flowers. It is often planted in yards to attract the iconic monarch butterfly, which lays its eggs on the milkweed as a food source for their larvae.
However, tropical milkweed, which is not native to Florida or anywhere else in North America, has recently raised concerns among botanists and butterfly enthusiasts about its effect on the monarch butterfly population, possibly causing more harm than good.
Monarchs have been making news in recent years alongside evidence of declining populations. The federal government is due to revisit a designation of the monarch as in need of protection by Dec. 4, NPR reported. That's when the U.S. Fish and Wildlife Service (FWS) has to update its Federal Register. Many monarch experts and enthusiasts are hoping that the butterfly will be listed as threatened under the Endangered Species Act.
What fans of the flutterers might not realize, though, is that the very plants hobbyists buy at local nurseries to attract monarchs could be making things worse.
Milkweed is the sole host plant for monarch caterpillars and historically monarchs have relied on native milkweed species in aiding their migratory patterns. Tropical milkweed is not native to Florida and unlike native species, can persist year-round, creating a continuous food source for the monarch butterfly.
“There are several species of native milkweeds; they just aren't superabundant, ” said James Lange, a botanist, certified arborist, and botanical consultant at the Fairchild Tropical Botanical Garden in Coral Gables.
Finding native plants is difficult for the backyard hobbyist and many people don’t have the time or inclination to research plants that will be eaten in a matter of weeks. Additionally, the native milkweed dies off at the first frost, and those looking to provide food for overwintering monarchs prefer to have plants year-round. Milkweed native to Florida also tends to like “wet feet,” meaning they prefer their root system to be constantly moist. This also proves difficult for backyard enthusiasts since most people don't have access to a swamp in their yards. Native milkweed is a much harder sell for nurseries than tropical milkweed, and nurseries are in the retail and wholesale business to make a profit.
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Monarch butterflies have historically been migratory insects, traveling thousands of miles from North America to Mexico in the winter. The presence of tropical milkweed year-round can interfere with this natural migratory cycle, causing the monarchs to remain in one place instead of traveling to their appropriate wintering and breeding locations.
“Historically, a lot of the research points to that Florida was never really an important part of the monarch migration,” Lange added.
Tropical milkweed not only interferes with the insect's migratory patterns, but it also harbors a parasite known as Ophryocystis elektroscirrha, or OE. This parasite accumulates on non-native milkweeds and increases the risk of infection for monarch butterflies feeding from it. Monarchs that contract this disease are deformed and often die upon emerging from their chrysalis. Additionally, monarchs feeding solely on tropical milkweed are more likely to contract and spread the disease.
This begs the question of whether monarchs belong in Florida in the first place. In propagating the tropical species of milkweed, well-meaning butterfly enthusiasts in Florida are unwittingly damaging the species and interfering with the migratory patterns and breeding prospects of the monarch. This small breeding pool, feeding solely on tropical milkweed, doesn’t allow for any variation of the species and simply proliferates the problems facing the monarchs as a whole.
Those raising captive monarchs are also furthering this infection. In order to survive, monarch caterpillars need to consume milkweed at a constant rate, tending to leave milkweed plants bare within a day or so. Captive breeders have to keep up with their diet, and the easiest way to do so is by purchasing tropical milkweed since it is so abundant and has a much faster growth rate.
“I know people who raise captive butterflies,” said the owner of a native plant nursery, who prefers their business not be named, “and they do have the ability to test the monarchs for OE before release. Do I know anyone who does that? No.”
The debate over whether tropical milkweed should be sold in Florida native nurseries is a huge controversy in the butterfly and plant community. One Florida native nursery was willing to talk on the subject but was hesitant to release their name and the name of their company due to potentially being dropped by FANN, the Florida Association of Native Nurseries. This reluctance to speak on the record points to the problem of a nurseries’ need to make a profit and to sell what customers will buy. Keeping only pure native stock risks losing a good deal of business from the backyard butterfly enthusiasts, who have legion since the pandemic.
Butterfly World in Coconut Creek did not return requests for comment.
People craving a hobby during lockdown turned to many things, one of which was trying to save the endangered monarch. In Florida, this often meant purchasing a lot of tropical milkweed. Despite knowing that tropical milkweed is putting monarchs in danger, nurseries continue to supply it because the public wants to buy it.
The native plant nursery employee who was unwilling to be named said that butterfly enthusiasts may mean well, but that’s not good enough. “Their feel-good feeling,” the employee said, “should not take precedence.”
This story was produced by MediaLab@FAU, a project of Florida Atlantic University School of Communication and Multimedia Studies, as part of a content sharing partnership with the WLRN newsroom. The reporter can be reached here.
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