Plants perennial, often matted, rhizomatous. Stems prostrate to ascending or erect, usually diffusely branched, sharply 4-angled, (5–)25–50 cm, glabrous to finely papillate, rarely pubescent. Leaves sessile; blade linear-lanceolate to ovate-lanceolate, rarely elliptic-lanceolate, 1–6 cm × 2–8 mm, base cuneate, margins eciliate or scabrid, sometimes ciliate towards base, apex acute. Inflorescences with flowers solitary, terminal and axillary, or terminal, often copious, very lax, leafy cymes; bracts foliaceous, lanceolate, reduced distally to ca. 2 mm, ± scarious. Pedicels erect or patent, usually reflexed at maturity, 10–40 mm, glabrous. Flowers 3–5 mm; sepals 5, 1–3-veined, lanceolate to ovate, 2–5 mm, margins scarious, apex acute, glabrous; petals 5, rarely absent, white or translucent, 1–3 mm, usually shorter than sepals; stamens 5; styles 3, erect to spreading, 0.9–2 mm. Capsules greenish brown or straw colored, ovoid, 3–7 mm, more than 1–1.5 times as long as broad, exceeding sepals, apex acute, opening by 3 valves; carpophore very short or absent. Seeds 10–20, brown, obovate, 0.7–0.9 mm on longest axis, smooth or slightly rugose. 2n = 52.
Alta., B.C., Man., N.B., N.S., N.W.T., Nunavut, Ont., P.E.I., Que., Sask., Yukon, Alaska, Calif., Colo., Conn., Idaho, Maine, Mass., Mich., Minn., Mont., N.H., N.J., N.Y., Nev., Oreg., Pa., R.I., S.Dak., Utah, Vt., W.Va., Wash., Wis., Wyo., Circumboreal.
Subspecies 2 (2 in the flora).
Plants infected with an anther smut, Microbotyrum stellariae (Sowerby) G. Deml & Oberwinkler [Ustilago violacea (Persoon) Roussel, in the broad sense], exhibit flowers with enlarged, reddish anthers. This condition is known in both subspecies, especially in northern areas of the range, but is as yet unknown in Stellaria calycantha, a species previously united with S. borealis by some authors.
|1||Sepals ovate to ovate-triangular, with midvein extending to near apex, lateral veins visible only at base; capsules dark brown, opaque, less than 2 times as long as wide, usually 3-4.5(-5) mm; leaf blades elliptic-lanceolate to narrowly elliptic or linear-lanceolate, widest just below middle, usually 2-3 cm; circumboreal||Stellaria borealis subsp. borealis|
|1||Sepals narrowly triangular, with 3 prominent, ridged veins extending to near apex; capsule straw colored, translucent, 2 times as long as wide, usually 5-7 mm; leaf blades narrowly lanceolate, widest near base, usually 3-6 cm; w North America||Stellaria borealis subsp. sitchana|