Spirogyra is the most diverse of the conjugating green algae, with more than 300 known species. Almost half of these can be found in North America. Spirogyra is commonly abundant in standing flowing waters of neutral or slightly acidic pH. The genus usually exists as loose, floating mats, and often forms extensive but harmless springtime blooms in freshwater ponds. Spirogyra, Mougeotia, and the desmids frequently inhabit the low pH waters of Sphagnum bogs.

Spirogyra filaments are sometimes invaded by parasitic protists.