The royal fern, or Osmunda regalis spectabilis, is a perennial, deciduous fern with green, leaves that get to three to five feet tall that grow in an erect manner. Each plant contains one compound leaf or a tuft of such leaves. The plant looks much like a shrub until observed more closely. The royal fern prefers shade to partially shady conditions with plenty of moisture. The royal fern remains hardy from zones three to nine.
The young leaves and petioles emerge covered with wooly hairs that become glabrous as they mature. These petioles appear light green, tannish-yellow, or brown. These petioles look flattened at their bases and terete throughout the remainder of the leaf.
The royal fern produces both sterile and partially fertile leaves
More sterile leaves get produced by the plant than fertile fronds. Each leaf grows to a length of three and a half feet, and two and a half inches across. The leaves appear deltate in their outline.
The sterile leaves are bipinnate or tripinnate and include six to nine pairs of pinnate leaflets or two to three pairs of bipinnate leaflets. Pinnate leaflets of the royal fern have eight to 15 pairs of subleaflets that conclude in a terminal leaflet. These leaflets aren’t directly opposite of each other, however. Subleaflets range in size from one to two inches long and about one-third of their length wide. These subleaflets are either oblong or lanceolate in shape and smooth around their outer edges.
The top surfaces of the subleaflets look either yellow-green or medium green. The lower leaves look pale green to almost white. Tips of the subleaflets range from blunt to obtuse, while the bases appear somewhat rounded. They also have one or two basal lobes.
The sporangia of the royal fern vary from pale yellow to reddish brown. The spores themselves look bright green.