Nymphoides aquatica and Nymphoides cristata

Menyanthaceae

Out and about today, the pretty encounter was with Crested Floating-Heart floatin’ & flowerin’ along the shores in the Winding Waters Natural Area. They look like little Water-Lilies but are unrelated, merely sharing convergently a similar lifestyle and consequent appearance. Crested Floating Heart, N. cristata, is not native. It appeared in S Florida maybe 30 years ago, probably dumped from aquariums,  has spread to other states, and in places can overdo it a bit. 

Crested Floating Hearts is so similar to the native Floating Heart, N. aquatica, the two can be a challenge to distinguish.  Most obviously, the crested invader has a wavy white wing like the fin on an eel rising from each petal.

Nymphoides cristata tends toward slightly more-elongate leaf blades.  Trouble is, the size of the “fin” varies, and S. aquatica has a ridge on its petals.   The similarity of the two species is certainly one example of many of close similarities between plants of eastern North America and eastern Asia.

A more subtle difference is in the flower structure.  Nymphoides aquatica is dioecious, that is, has separate male and female plants.  Nymphoides cristata, by contrast, has bisexual flowers with both sexes together, at least so far as known in Florida.   Across its much broader range, the breeding system varies, and having been introduced to Florida more than once, it may have some surprises if studied statewide.   The flowers in Winding Waters today were bisexual.

In the aquarium world, Nymphoides aquatica has the name “Banana Plant,” because the floating plants form banana-shaped roots in the water up near the leaves.    Nymphoides cristata has tuberous roots too, but thinner.  In both species, the tuberous roots break off and disperse the plants.

In tropical Asia where N. cristata is native, it has some value as a food, although please do not try that, as it also contains bioactive compounds, including ephedrine and coumarins.   In years of studying plants, you see just about every conceivable use, but one “new to me” is grinding the plants with oil to use as a salve on bug bites.    I’m tempted to try that.