Acmella americana Flowers!

I was very excited this weekend to discover that a plant out in my pond was flowering! This particular plant was collected down in Texas in 2009, and a few of us have been growing it in our aquariums ever since, not knowing what its identity was.

We didn’t actually know we collected it until we got home, sorted through some other plants, and found a single stem in with everything else. In fact, I wasn’t even sure if it was an aquatic plant at first, but sure enough, it grew, albeit slowly. 

With the flower, we now believe the identity of this plant is likely Acmella americana, which has also been known as Spilanthes americana and Acmella oppositifolia over the years.

Submerged, Acmella americana grows a lot like Hyptis lorentzianai, except that it stays lime green in coloration. The growth rate and pattern is similar to Hyptis, in that the leaves stay much smaller under water, relative to their terrestrial size.

Additionally, emersed the stems tend to creep horizontally, but in the aquarium they are much more upright, with longer distance between the nodes. Due to that distance, use in aquascaping would require several stems growing together like you would grow purple bamboo or the true Rotala indica.

I’m very happy to finally get a lead on a plant ID after finding this plant 18 months ago. Now that we have a likely ID, I’m going to try to grow it out, and have some others try using it in their aquascapes to truly find out whether or not it’s a viable plant for the aquascaping hobby. Apparently, Acmella americana has been available in the pond hobby for some time, so it should be readily available to anyone looking to try it out. Comments welcome!