Dichotomous key to European species of Sphagnum Part 1

Dichotomous key to European species of Sphagnum Part 1

Dichotomous key to European species of Sphagnum Part 1

Taken from the book "Handbook of European Sphagna, ed. 2 - Institute of Terrestrial Ecology"


Cortical cells or branches (and usually at least the internal one of stems) with spiral fibrils. Apices of branch leaves blunt and hooded, appearing minutely roughened. On the convex surface due to projecting, partly resorbed, hyaline cells. Plants usually robust.

Section Sphagna 2

Cortical cells without fibrils. Branch leaf apices usually acute, truncate or, if hooded, then smooth on the convex surface. Plants robust or small.


2 - Section Sphagna

Internal commissural walls of branch leaf hyaline cells (at least in the lower lateral parts of leaves) with papillae or sparse to dense lamellae or crests (ie appearing as though the photosynthetic cells have papillose or ornamented walls). Plants green, yellow, ochre or brown, never crimson.


Internal commissural walls smooth throughout. Plants, except for capitula, usually green or  crimson-tinted.



Internal commissural walls finely to rather coarsely papillose. Photosynthetic cells in TS, urn-shaped with oval lumina and thick adaxial walls. Plants often ochrous: widely distributed and locally abundant on oligotrophic to slightly mesotrophic mires.

Sphagnum papillosum

Internal commissural walls with scattered dense, oblique to transverse crests or lamellae ('comb fibrils'). Photosynthetic cells in TS, broadly triangular with triangular lumina: thin-walled. Plants dull brown to orange-brown, rarely green or yellowish: local to rare in, mainly lowland, oligotrophic to slightly mesotrophic mires.

Sphagnum imbricatum


Plants usually with at least some flecks of crimson, often entirely deep, wine-red. Spreading branches usually blunt. Photosynthetic cells not, or rarely, exposed on the concave leaf surface: in TS, oval and mostly enclosed by hyaline cells. Plants widespread but local (and then often abundant) on oligotrophic mires.

Sphagnum magellanicum

Plants never red (sometimes pinkish-brown or grey-purple, especially in the capitulum). Spreading branches long-tapering. Photosynthetic cells well exposed on the concave leaf surface: in TS, trapezoid to narrowly oval-triangular. Plant common in mesotrophic mires or parts of mires.

Sphagnum palustre


4a - Sphagnum palustre

Photosynthetic cells in TS oval-triangular to trapezoid: thin-walled. Plant widespread and common in the south: becoming rarer further north.

Sphagnum palustre

var. palustre

Photosynthetic cells in TS, oval to urn-shaped with strongly thickened adaxial walls. Plant widespread in the north (ie boreal and sub-arctic): confined to montane areas further south.

Sphagnum palustre

var. centrale


Branch leaves large (more than 1.5 mm) and broad. Hyaline cells of upper mid-leaf romboid, not more than 5 times longer than wide. Stem cortex 2-or more layered. Photosynthetic cells oval in TS, immersed or almost so.


Branch leaves narrow or, if broad, then hyaline cells.long and narrow, more than 6 times as long as wide, and stem cortex usually 1-layered. Photosynthetic cells (except S. wulfianum) obviously exposed on one or both surfaces.



Branch leaves large. Stem leaves very small (< 1.1mm), triangular: convex surface of hyaline cells intact. Branch cortical cells all alike, most or all with a single large pore. Capitula ± hidden among upwardly directed branches.

Section Rigida 7

Branch and stem leaves of similar size. Stem leaves lingulate to rectangular: convex surface of hyaline cells resorbed. Branch cortical cells of 2 kinds; groups of 2-3 retort cells (large cells each with a distal, protuberant pore) and smaller, narrower imperforate cells. Capitula not ± hidden.

Section Insulosa Sphagnum aongsroemii

7 - Section Rigida

Branch leaf photosynthetic cells deeply immersed between hyaline cells: in TS, thin-walled, oval. Internal commissural walls smooth. Older stems dark brown. Plants densely tufted: widespread and common, typically on wet heath or along the margins of flarks (large pools in patterned boreal


Sphagnum compactum

Branch leaf photosynthetic cells narrowly exposed, at least on the convex leaf surface: in TS, with thickened abaxial walls. Internal commissural walls minutely papillose. Stems pale. Plants usually pallid with squarrose branch leaves: local to rare on shallow peat near Atlantic coasts.

Sphagnum strictum


Fascicles of mature plants consisting of at least 7 (usually 8 or more) branches. Stem leaves small (less than 1.2 mm). Photosynthetic cells in TS, oval. Plants rigid with dense, acute branch leaves and conspicuously large capitula. A continental species of moderately wet coniferous forest

and, rarely; damp heath.

Section Polyclada Sphagnum wulfianum

Fascicles never with more than 7 (usually fewer than 6) branches. Stem leaves usually over 1.2 mm long. Photosynthetic cells in TS, triangular, trapezoid or barrel-shaped. Capitula small to  well-developed.



Photosynthetic cells in TS, triangular or trapezoid with widest exposure on convex leaf surface, or ± barrel-shaped and ± equally exposed on both leaf surfaces. Plant, if small-leaved, not red.


Photosynthetic cells in TS, triangular or trapezoid with widest exposure on concave leaf surface. Includes small-leaved (ie under 1.6 mm long) red plants.

Section Acutifolia 34


Stem leaves large, lingulate, never fibrillose in mature plants; border not expanded below. Plants often robust, with large branch leaves that may be abruptly narrowed and reflexed at mid-leaf. Never red.

Section Squarrosa 11

Stem leaves various, if lingulate and efibrose, then with borders markedly expanded below. Branch leaves rarely squarrose. Plants sometimes red, then with very large (>2 mm long) branch leaves


11 - Section Squarrosa

Branch leaves small (less than 2.2 mm long), usually with apices erect or only slightly spreading (if squarrose, then branches long and attenuated) so that branches appear cylindrical and tumid. Plants green or, usually, brownish. A local to frequent species (common in the Arctic) of eutrophic mires.

Sphagnum teres

Branch leaves large (usually over 2.3 mm long), usually distinctly squarrose, giving the plant a prickly appearance. Plants green or yellowish, rarely brownish, robust. Common in mesotrophic mires.

Sphagnum squarrosum


Mature plants without branches or with, at most, 1-2 short, small-leaved branches per fascicle. Stem leaves much larger than branch leaves, overlapping and concealing stems. Leaves sometimes with resorption gaps but never with clearly defined pores. Plants purple to blackish or dark brown, rarely dull olive-green: ± aquatic: very rare in NW France and NW Spain.

Section Hemitheca Sphagnum pylaesii

Mature plants with well-developed fascicles, rarely of fewer than 3 branches (if fewer, then stem leaves not conspicuously larger than branch leaves, not concealing stems, or at least some branch leaves with clearly defined pores).



Branch leaf hyaline cells short and proportionately broad (less than 6 times as long as broad). Stem leaves almost as large as branch leaves, both ovate and concave. Branches appearing 'beaded' because of widely spaced, concave branch leaves. Plants small, delicate and pale green or yellowish. A common species of damp oligotrophic mires and wet heath.

Section Mollusca Sphagnum tenellum

Branch leaf hyaline cells long and narrow (at least 6 times as long as broad). Stem leaves various but, if similar to branch leaves, then plants not delicate. Branches not 'beaded' Plants mostly of medium size or robust.



Leaves from middle of branch, ovate, less than twice as long as wide, with broad, ± hooded apices (if narrower, then stem cortex with pores). Branch leaf hyaline cells with few to numerous small, normally

thick-ringed, pores along the commissures.on the convex or both leaf surfaces (very rarely only on the concave). Photosynthetic cells of branch leaves almost equally exposed on both leaf surfaces.

Section Subsecunda 15

Leaves from middle of branch, lanceolate, at least twice as long as wide, never with hooded apices (apices often apparently acute due to inrolled margins). Stem cortex never with pores. Branch leaf hyaline cells with pores various but rarely numerous on convex leaf surface, and then not normally along the commissures. Photosynthetic cells with much wider exposure on the convex leaf surface, often not reaching the concave surface.

Section Cuspidata


15 - Section Subsecunda

Stem leaves ± as large as branch leaves, strongly fibrillose almost or quite to insertion. Stems pale, greenish, yellowish or pale brown, never dark brown or blackish. Plants medium-sized to robust, ± flaccid.


Stem leaves much smaller than the largest branch leaves, sometimes minute, fibrillose in the upper two-thirds at most. Stems pale or dark. Plants sometimes small.


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