This arrowhead typically produces narrow leaves, though exceptions occur. As its common name suggests, it would grow in more acid habitats, as compared to common arrowhead, though the two can be found in close proximity. On the Ponkapoag Bog, acid-water arrowhead grows right on the Sphagnum mat, while common arrowhead prefers open-water gaps in Sphagnum. The heads are "strongly echinate", that is, bristly, like hedgehogs or porcupines.