Osmunda regalis Linnaeus

Royal fern, flowering fern

Etymology Regalis means regal, or of outstanding merit.
Description Rhizome: erect, massive, forming a trunk, occasionally branching, hairs and old stipe bases woven together with black, fibrous roots.
Frond: 120 cm high by 25 cm wide, though sometimes much taller, deciduous, dimorphic, blade/stipe ratio: 1:1.
Stipe: stipules (flared leaf base), unique to the family/genus, hairy when young, soon glabrous, vascular bundles: 1 in a U-shape where the top of the arms continue to curl.
Blade: 2-pinnate, rachis grooved, somewhat waxy, shedding water, reddish to light brown hairs, soon falling.
Pinnae: 5 to 9 pair, catadromous, often jointed at the rachis, rotated to the horizontal; on fertile fronds usually the two to four lowest pair are sterile; pinnules oblong, to 8 cm, 8-12 pairs plus a terminal pinnule; margins almost entire, the tip of the pinnules serrate; veins free, forked.
Sori: none, indusium: absent, sporangia: large, globose, tan or black when mature, spores green, maturity: early to midsummer.
Dimensionality: horizontal pinnae.
Culture Habitat: wet, acidic swamps, bogs. Distribution: Europe and northern Africa, eastern North America. Hardy to -40°C, USDA Zone 2.
Distinctive Characteristics Distinguished from other Osmunda by having fertile pinnae above sterile pinnae and 2-pinnate; distinguish from all other ferns by the generic characters: no sorus, no indusium, naked sporangium, winged stipe bases.
Osmunda regalis
Osmunda regalis. upper half of frond with sporangia; top left: partially fertile segment; top center: open sporangia; top right: branched hair from unfolding frond; bottom left: vascular bundle in the rachis.  Illustration from Scandinavian Ferns by Benjamin Ĝllgaard and Kirsten Tind, Rhodos, 1993.
var spectabilis The North American version has thinner, more distant segments, and fewer hairs. The European variety, regalis, is stouter and very much larger, up to 2 meters or more in bogs.
Osmunda regalis
Osmunda regalis. Left to right: gametophyte, first flabellate frond; emergence; base of petiole with flanges and dripping mucillage.  Illustration from Scandinavian Ferns by Benjamin Ĝllgaard and Kirsten Tind, Rhodos, 1993.
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