Synonyms: Aphyllocalpa regalis, Osmunda mexicana, Osmunda palmeri, Osmunda spectabilis.

The Royal Fern is the largest and most spectacular North American fern. Its large size, longevity and the distinctly different sterile and fertile parts make this species an ideal accent plant for landscaping.

Its bright green fronds are divided with broad, oblong-shaped leaflets. The mature plant shows rust-colored flower spikes. Young fronds (leaves) are covered in a hairy felt as they emerge, but become hairless at maturity. This fern is unusual in that it forms new fertile fronds in autumn, and not in spring or summer as is common in most ferns.

This deciduous herbaceous plant produces separate fertile and sterile fronds. The sterile fronds are spreading, 24-60 inches tall and 12-16 inches broad, bipinnate, with 7-9 pairs of pinnae up to 12" long, each pinna with 7-13 pairs of pinnules 1 - 2 1/2" long and 1/2 - 3/4" broad. The fertile fronds are erect and shorter, 8-20 inches tall, usually with 2-3 pairs of sterile pinnae at the base, and 7-14 pairs of fertile pinnae above bearing the densely-clustered sporangia.

It requires moist soil. It can form large colonies and always grows near water, even along rivers and streambanks where the rhizome is continually bathed in running water. It is native to woodland and forest, but generally requires fairly high light intensity.

Plants have a massive creeping rhizome (root system) and the rootstock can protrude several centimeters above the ground like a short trunk covered with leaf sheaths and roots. Winter dormant. Slow to moderate growth rate. Symmetric clumps, spreads slowly. Spacing: 24"-60". Mature height 24"-60".