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juniper haircap moss, juniper polytrichum moss

Habit Plants small to medium to fairly robust, gray-green to bluish green to reddish brown with age, in loose tufts, often forming extensive patches. Plants rather fragile, forming extensive green carpets or as scattered stems among other bryophytes.

(1–)4–5(–10) cm, simple, brownish tomentose only near the base.

3–12 cm.


3–6(–8) mm, densely imbricate, ± erect and almost straight when dry, erect-spreading to widely spreading when moist;

sheath oblong-rectangular, yellowish, tapering to the blade;

blade slender, bluish green and nitid, rather flat, with sharply infolded margins;

marginal lamina 5–7 cells wide, 1-stratose, entire or minutely crenulate, membranous and transparent, enclosing the lamellae and overlapping towards the apex;

costa usually somewhat toothed distally, excurrent, forming a subulate, toothed awn, the awn reddish brown throughout or slightly decolorate at tip;

lamellae bluntly crenate in profile, 6–8 cells high, the marginal cells in cross-section ovate to pyriform, thick-walled, ending in a distinct knob, smooth or rarely faintly papillose, the marginal cells of lateral lamellae (enclosed by the overlapping margins) ovoid and less strongly thickened;

sheath cells 70–100 × 6–10 µm, narrowly rectangular (4–6:1), narrower toward the margin;

cells of the broad marginal lamina transversely elongate, very thick-walled.

(4–)6–10 mm, ± distant, not crowded; closely appressed, straight or erect-spreading and weakly flexuose when dry, erect-spreading to widely spreading or weakly recurved when moist, caducous at the base of blade;

sheath short, scarcely broadened and rather weakly differentiated;

marginal lamina narrow, 2–3 cells wide, erect to somewhat involute towards the apex, entire to finely and obscurely serrulate from the middle upwards, the teeth rather weak and distant;

costa smooth abaxially, ending in a short, weakly toothed tip;

lamellae crenulate in profile, 8–12 cells high, with paired, projecting knobs along the margins, the marginal cells in section rather narrow, retuse, thick-walled, brownish, smooth;

sheath cells rather short rectangular, 60–90 × 15–22 µm;

cells of the marginal lamina ± isodiametric;

perichaetial leaves with sheathing bases usually hidden by upper stem leaves.


(1–)3–5 cm, stout, yellowish to reddish brown.

1.5–4.5 cm, brownish.

Sexual condition


perigonial rosettes yellowish to reddish green;

perichaetial leaves longer than the foliage leaves, long-sheathing, the blade almost obsolete, ending in a slender yellowish or hyaline awn.


2.5–5 mm, rectangular, longer than wide (1.5–2:1), reddish brown to dark brown, glaucous when fresh, suberect, becoming horizontal when mature, sharply 4-angled and prismatic;

peristome 200–240 µm, divided to 0.6–0.8, the teeth 64, keeled at back.

2.5–3.5 mm, sharply 4–5-angled, short rectangular to cubic.


whitish to light brown, covering the capsule.


6–10(–12) µm.

Polytrichum juniperinum

Polytrichum jensenii

Habitat Exposed, well-drained, mostly acid soils in old fields and open woods, in openings following forest fire, on trailside banks and road cuts, on thin shallow soil overlying rocks, blowdowns and open ridge tops near timberline, only rarely in moist or wet situations Periodically flooded areas, bogs, sedge meadows, margins of lakes, streams and rivers
Elevation low to high elevations low to moderate elevations (0–1500 m) (low to moderate elevations (0–4900 ft))
from FNA
AK; AL; AR; AZ; CA; CO; CT; DE; GA; IA; ID; IL; IN; KS; KY; MA; MD; ME; MI; MN; MO; MT; NC; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; UT; VA; VT; WA; WI; WV; WY; AB; BC; MB; NB; NL; NS; NT; NU; ON; PE; QC; YT; Mexico; Central America; c Asia; Australia; Pacific Islands (New Zealand); Atlantic Islands (Macaronesia); Greenland; n Asia; Europe; s South America; West Indies; Antarctica
[WildflowerSearch map]
from FNA
AK; WY; LB; NT; NU; QC; YT; Greenland; Arctic Europe; Asia (n Russia)

Polytrichum juniperinum occurs on a variety of substrates, but primarily in dryer situations than P. commune or P. strictum. It often forms extensive pure stands of a distinctive pale bluish green color from the reflection of light off the thin, membranous margins of the leaves. The narrow leaf blades are widely spreading and have short, reddish awns. Polytrichum juniperinum is common and generally distributed throughout continental North America. In the high Arctic, however, the species is rare and many older reports of it actually pertain to 5. P. hyperboreum (D. G. Long 1985).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Polytrichum jensenii is a widely distributed plant of the high Arctic, with a sporadic disjunct occurrence southward, where its distribution is poorly documented. In Nunavut, it is known from Melville Island. In arctic America it replaces P. commune north of the tree line (D. G. Long 1985, as P. commune var. diminutum), and is notable for its rather fragile texture, entire to weakly toothed leaf margins, and caducous leaf blades. The marginal cells of the lamellae are similar to those of P. commune. Forms of P. swartzii have entire or nearly entire, caducous leaves, but the marginal cells of the lamellae are rounded quadrate and thin-walled, absent the distinctive, thickened knobs of P. jensenii and P. commune. Genetic evidence may support the recognition of P. jensenii as a distinct species (G. S. Derda and R. Wyatt 1999).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 27, p. 138. FNA vol. 27, p. 137.
Parent taxa Polytrichaceae > Polytrichum Polytrichaceae > Polytrichum
Sibling taxa
P. commune, P. hyperboreum, P. jensenii, P. piliferum, P. strictum, P. swartzii
P. commune, P. hyperboreum, P. juniperinum, P. piliferum, P. strictum, P. swartzii
Synonyms P. alpestre, P. juniperinum var. alpestre, P. juniperinum var. waghornei P. commune var. jensenii, P. commune var. diminutum, P. commune var. yukonense, P. yukonense
Name authority Hedwig: Sp. Musc. Frond., 89, plate 18, figs. 6–10. (1801) I. Hagen: Meddel. Grønland 15: 444. (1897)
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