Asterionella formosa has valves (siliceous plate that makes up a half of a diatom cell) that are long and narrow, with capitate (enlarged and rounded) apices (tips) unequal in size.

[4] Asterionella formosa colonies consist of cells joined at their valve faces' footpoles by mucilage pads.

[3] Asterionella formosa colonies may be colonized by small, sessile (non-mobile) choanoflagellates, or infested by Zygorhizidium planktonicum, a parasitic chytrid fungus.

[4] A. formosa laboratory models have been observed to have dynamic microbiomes with many bacterial species, mostly from the phyla Proteobacteria and Bacteroidetes.

Such increases in A. formosa populations have been used by North American researchers to determine whether a nitrogen disposition rate in a given lake can cause significant ecological effects.