All fronds grow from a single black knob.
Similar species: Cinnamon Fern (Osmundastrum cinnamomeum) - grows in wetter areas, has white-velvety lower stems; does not grow from a single black knob. Interrupted Fern (Osmunda claytoniana) - does not have a separate fertile frond; does not grow from a single black knob. Marsh Fern (Thelypteris palustris) - smaller; crooked stem; fronds grow singly; grows in wetter areas. Virginia Chain Fern (Woodwardia virginica) - uncommon; fronds grow singly.
Classic Ostrich Fern shape and growth form. Note that this one is in standing water. They will grow in wet areas if the area is only wet for a while in the spring. This photo was taken at the end of May.
Nice patch of Ostrich Fern in a clearing in the woods.
Note how all the fronds/stalks grow from a single point - a black knob.
Here's a closeup view of this black knob. This is in mid-April, before the fiddleheads start to grow.
Ready to pick and eat. Ostrich Fern is common enough that its fiddleheads can be harvested for personal use without worrying too much about eradicating the species. Of course, prudence is always in order when harvesting any wild plants.
Too far gone to eat.
Typical frond shape. Note how the tip narrows abruptly.
Closer view showing how the tip of the frond narrows abruptly and comes to a rather blunt point.
Underside of a frond.
Underside of a leaflet.
Fertile frond. In Ostrich Fern these are separate and quite different from the infertile fronds.
Last year's fertile fronds. They're black and easily spotted the next spring as they persist through the winter.
Closeup view of an old fertile frond.
Some fertile fronds from the previous year scattered along a stream bank in late April.