E-Flora BC: Electronic Atlas of the Flora of British Columbia

Dryopteris expansa (C. Presl) Fraser-Jenkins & Jermy
spiny wood fern (spreading wood fern; spreading woodfern)
Dryopteridaceae (Wood Fern family)

Introduction to Vascular Plants

© Kevin Newell  Email the photographer   (Photo ID #5388)

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Distribution of Dryopteris expansa
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Species Information

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Deciduous perennial arising in vase-like clusters or singly.
Triangular to oblong-triangular, 20-70 cm long, 10-60 cm wide, sparsely glandular on rachis and lower side of pinnae, 2- to 3-pinnate, the lowest pinnae longer than the upper ones, leaf outlines triangular.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Mesic to wet forests, forest margins and scree slopes from the lowland and steppe to subalpine zones; common in BC; circumpolar, N to AK, YT and NT, E to NF, S to MI, WI, MN, CO, ID and CA; Eurasia.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Dryopteris expansa

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class




Elevation (metres) 0 737 2750
Slope Gradient (%) 0 23 410
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
0 350 360
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
0 4 8
Modal Nutrient Regime
Number of field plots
 species was recorded in:
Modal BEC Zone Class
All BEC Zones (# of stations/zone) species was recorded in: BAFA(1), BWBS(36), CDF(72), CMA(1), CWH(2243), ESSF(1067), ICH(1419), IDF(59), MH(59), MS(79), SBPS(3), SBS(645)

Ecological Indicator Information

A shade-tolerant, submontane to subalpine, circumpolar fern (transcontinental in North America). Occurs on fresh to very moist. nitrogen-medium soils within boreal, cool temperate, and cool mesothermal climates; its occurrence increases with increasing pre­cipitation. Common and occasionally dominant in coniferous forests on water-shedding and water-receiving sites; often inhabits decaying wood. Associated with Blechnum spicant, Polystichum munitum, Rhytidiadelphus loreus, and Vaccinium alaskaense. Characteristic of friable Mor and acidic Moder humus forms.

SourceIndicator Plants of Coastal British Columbia (Information applies to coastal locations only)


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Dryopteris assimilis S. Walker
Dryopteris dilatata auct. non (Hoffm.) A. Gray
Dryopteris dilatata subsp. americana (Fisch.) HultΘn
Dryopteris spinulosa subsp. assimilis
Dryopteris spinulosa var. dilatata auct. non (Hoffm.) Underw.

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References