The first time I saw an air potato vine, I said to myself, “Now there’s a handsome plant.” And why not? The bold, heart-shaped leaves have an attractive shine and interestingly quilted surface. The strange little potato-like balls hanging from the vine weren’t very pretty, but the leaves grew so thickly you barely noticed them.
I wasn’t the first person to make this mistake. Air potato (Dioscora bulbifera) is another plant on the long, long list of exotics that make themselves at home in the Florida wilds. The plant is native to tropical Asia, but it was actually brought here from Africa in 1905 as a potential food crop.
Horticulturists and scientists working with the plants noted several things. First, it grew incredibly fast — as much as 8 or 10 inches a day. Second, it wasn’t bothered by insects, which mostly avoided it. Third, although it’s in the true yam family (which, FYI, does not include sweet potatoes), it wasn’t producing anything edible. Reports of the tubers as a food source may have mistaken the air potato for a similar species (D. alata) that has been grown for millennia by tropical farmers.
Unfortunately, some of them also noticed what I did: It’s a good-looking plant. So they brought starts home for their gardens, and sent some to green-thumbed friends. Soon, they discovered that once you get air potato established, it’s nearly impossible to eradicate.
Each potato-like bulbil has the ability to become a new plant, and a single vine may bear many hundreds. Once it roots, the plant forms a large underground tuber, which can support dozens of vines. This tuber can be dug up, but any piece of root left in the ground will sprout. Also, anywhere the vine touches soil, a new tuber will form.
An air potato stem is a weak, floppy thing. For support, the vine climbs anything within reach. Its clinging tendrils, unlike the stem, are very tough and hold fast to all but the smoothest surfaces. Within a few weeks, a new air potato start can reach the top of a tall tree. The vine can grow as long as 90 feet, so it’s capable of reaching the crown of almost any tree in the state.
That’s when the real problems start. Once it’s reached its place in the sun, an air potato grows so bountifully it blocks sunlight from reaching the tree or shrub that it has climbed. Starved of light, the host plant begins to suffer. Fortunately, the vine dies back each winter, but with summer being the maximum growth season, air potato will stunt (if not outright kill) trees growing alongside it. The vine also prevents other plants, many of which go dormant at the same time, from growing at all.
In 2007, USDA agronimists working in Asia noticed that the air potato vines there were often full of gnaw marks — something never seen back in the states. An investigation revealed a small red beetle (Lilioceris cheni) was doing the munching. Better yet, they didn’t seem to be munching anything else.
They rounded up some beetles to send back to the U.S. for more tests. Specifically, they wanted to know if the bugs would eat anything else. By 2010, studies had proven they would not. Knowing they wouldn’t be unleashing a new pest to fight an old one, the Florida Department of Agriculture began plans for large-scale beetle production.
Since 2012, the FDA has released more than a half-million beetles all around the state. They’ve sent hundreds of thousands more to municipalities and homeowners who have requested them.
And they’re doing their job right in our backyards. The photos shown here were taken a couple weeks ago in the Murdock area of Charlotte County. Last year, the air potato vines grew unmolested. This year, they’ve got trouble. That’s a good thing for our native plants and the animals that depend on them.
Capt. Josh Olive is a fifth-generation native Florida Cracker and a Florida Master Naturalist, and has been fascinated by all sorts of wild things and places since he was able to walk. If you have questions about living with wildlife, contact him at Publisher@WaterLineWeekly.com or 941-276-9657.