In the Northeast, cinnamon fern is one of the easiest ferns to recognize when its cinnamon-colored spikes are still present. By late summer, the spike of cinnamon fern has crumbled away, and the fertile leaflets of interrupted fern have dropped off, leaving similar-looking vase-shaped ferns. This time of year, turn a frond over to look at where the base of the leaflet meets the stalk: cinnamon fern has a persistent tuft of tan hairs, while interrupted fern is smooth. A final tell is that cinnamon fern prefers wet soils, while interrupted fern is a generalist that will also grow in well-drained uplands. These matched those of the modern cinnamon fern almost exactly in size and number.