Mosquito ferns

Posted on February 10, 2023 12:19 PM by mfeaver mfeaver



Azolla is pretty difficult to distinguish at the species level, even for those of us who look at them constantly, so you are not alone!

In the southeast US, we have two native species complexes: Azolla filiculoides and Azolla cristata. There are further species under these, but without microscopes and certain other contextual information it’s not worth teasing them apart. It is perfectly acceptable to leave at the level of just these two taxa and call it a day. Here is how you can differentiate the two groups:

(1) Azolla filiculoides complex (includes A. caroliniana and A. filiculoides): is the larger and probably more common of the two. Its stem is more robust and pinnately branched, with leaflets in small alternating rows. The robust branching often leads to the tips of the fronds protruding above the water surface. [A good example looks like it is growing on top of itself];
(2) Azolla cristata complex (formerly A. microphylla , A. mexicana, and A. cristata): is smaller, less robust and sparsely branched (if so, they remain short). Leaflets distichous and much more dense/compact. Lays flat on the water surface.

Azolla pinnata is a tropical invasive, and can be distinguished from the above two primarily by it’s large size. A single plant might easily be 3-5 inches long/wide, whereas a very large and mature A. filliculoides might only be two inches in breadth. In morphology, essentially just like A filiculoides except the alternating pinnate branches are larger sized and much, much longer.

Hope this is helpful!

Jackman Corley

Posted by mfeaver over 1 year ago

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