The difference a ruffle can make. This is big floatingheart, Nymphoides aquatica. It has a cousin, crested floatingheart, Nymphoides cristata.
Big floatingheart is a rather benign and pretty Florida native. Crested floatingheart is pretty as well. In fact, it's almost identical in every way to cousin. It is not benign. It is an invasive that's becoming a big problem in parts of Florida.
The only way to tell them apart, at least from the surface, is by the ridge that runs down the middle of each petal. In crested floatingheart, the ridge, or crest, is ruffled. In big floatingheart, it's not.
The edges of the flowers of both plants are ruffled, by the way. Both have heart-shaped leaves that can have substantial amount of purple in them. The only other difference between the two is in the roots; if you turn big floatingheart over, you'll see banana-shaped roots, the inspiration for one of its other common names, the banana lily. If you can't get a close look at the roots or the flower, good luck telling them apart.
Big floatingheart, as noted, is a Florida native, found in most counties throughout the state. It's also found throughout the Southeast as far north as Maryland and Delaware and as far west as Texas. It is listed as endangered in Maryland, where it is known as large floatingheart, but its population is considered secure here in South Florida.
It's found in slow-moving waters, including sloughs, along the edges of ponds and lakes and in marshes and swamps.
Big floatingheart is used in landscaping, in water gardens and along the edges of ponds and lakes. It blooms in the spring and summer.
Big floatingheart is a member of Menyanthaceae, a family of aquatic plants that includes the buckbean. Other names include simply, floating heart.
Its crested cousin hails from Asia, including parts of Vietnam, China and Taiwan. It was brought here as an ornamental for water gardens and escaped into the wilds. Its distribution in the United States is limited to a few counties in Florida one lake in South Carolina and a part of Mississippi, but has the potential to spread throughout the Southeast. It is a major threat to recreational uses of ponds and lakes and other waterways.
There is another member of the family that closely resembles big and crested floatingheart, but it's only found in the Panhandle and points north.