Dryopteris expansa is one of 40 species of ferns found in the northern Pacific coast (Pojar & MacKinnon 1994). Ferns are distinct from flowering plants that produce seeds, instead they produce and disperse primarily through spores.
Description:
D. expansa has large triangular-shaped fronds (leaves) that arise from an underground stem (rhizome) each spring. The fronds are typically 20-70 cm in length and 10-60 cm in width. The entire fern plant can grow up to 1 m in height. Each frond is dissected three times to form leaflets (pinnae), with further dissections forming pinnules and lobes. The lowest pinnae are the longest, thus resulting in the characteristic triangular shape (Klinkenberg 2017). All fronds die back in the fall and new fronds appear in the spring.
Ecology:
D. expansa are commonly found in cool and moist temperate climates along forest margins and in clearings (Proudfoot et al. 2013). They can also be found growing at the base of rocky slopes or on tree stumps and rotting logs in the forest (Klinkenberg 2017).
Reproduction and Dispersal:
D. expansa, like all ferns, have a distinctive alternation of generations. Sexual reproduction occurs in a small gametophyte, from which the larger recognizable sporophyte plant grows. On the underside of each frond, clusters of spore-producing structures are formed. The small spores that are typically dispersed by wind or rain then develop into the small gametophyte (Soltis & Soltis 1987).
References Cited:
Klinkenberg B, editor. 2017. E-Flora BC: Electronic Atlas of the plants of British Columbia [eflora.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [accessed 2018 Jan 30]. http://linnet.geog.ubc.ca/Atlas/Atlas.aspx?sciname=Dryopteris%20expansa.
Pojar J, MacKinnon A. 1994. Plants of coastal British Columbia: including Washington, Oregon & Alaska. Vancouver: Lone Pine Publishing.
Proudfoot B, Brietzke C, Starzomski B. 2013. Spiny wood fern, spreading wood fern, spreading woodfern. Dryopteris expansa. Biodiversity of the central coast. [accessed 2017 Jan 20]. http://www.centralcoastbiodiversity.org/spiny-wood-fern-bull-dryopteris-expansa.html.
Soltis DE, Soltis PS. 1987. Breeding system of the fern Dryopteris expansa: evidence for mixed mating.
American Journal of Botany. 74(4):504–509.
Pojar J, MacKinnon A. 1994. Plants of coastal British Columbia: including Washington, Oregon & Alaska. Vancouver: Lone Pine Publishing.
Proudfoot B, Brietzke C, Starzomski B. 2013. Spiny wood fern, spreading wood fern, spreading woodfern. Dryopteris expansa. Biodiversity of the central coast. [accessed 2017 Jan 20]. http://www.centralcoastbiodiversity.org/spiny-wood-fern-bull-dryopteris-expansa.html.
Soltis DE, Soltis PS. 1987. Breeding system of the fern Dryopteris expansa: evidence for mixed mating.
American Journal of Botany. 74(4):504–509.