Galium aparine L., common bedstraw, stickwilly, cleavers, goose–grass. Annual, viney, taprooted, 1—several–stemmed at base, prostrate or decumbent, trailing and climbing over low plants; shoots weak–stemmed, extremely scabrous with minute, hooked prickles (barbs) along internode stem edges and blade margins and midribs.
Stems 4–sided and 4–ridged, to 2 mm diameter, never woody, sides convex, edges raised, nongreen and fibrous, with backward–pointing or hooked, very short stiff prickle–hairs (adhesive to itself and clothes).
Leaves whorled, 6 or 8 per whorl, simple and sessile, with stipules; stipules 2, indistinguishable from leaves (treated here as leaves); blade linear to narrowly oblanceolate, in range (4—)13—30+ × 1.5—4+ mm, bright green, margins somewhat inrolled under with downward–projected, hooked prickle–hairs (retrorsely hispid), short–acuminate with sharp point at tip, midrib only conspicuous and raised on lower surface, short–scabrous with hooks facing toward tip, lower surface scabrous along midrib.
Inflorescence dichasial cyme, axillary and paired at all branchless nodes, or unequal dichasia forming a leafy panicle, commonly congested at tip of main axis and appearing indeterminate, sometimes with a secondary dichasium in leaf axis and below an existing axillary dichasium, dichasium 15—130 mm long, to 4 orders of branching, typically with 1 pedicillate flower + 2 branchlets per node, bracteate (whorled at each node), with prickle–hairs as on shoot; peduncle 6—80 mm long, higher order axes reduced ca. 1/2 length of previous internode, axes 4–sided with retrorsely hooked prickle–hairs along ridges; bracts at each node whorled, leaflike, decreasing at higher order nodes; pedicel at anthesis < 0.5 mm long increasing to 15 mm long in fruit.
Flower bisexual, nearly radial, 2.2—3 mm across; perianth (corolla) 4–lobed, of 1 whorl, cymbal–shaped (rotate), whitish; tube ± 0.2 mm long, greenish at base; lobes spreading, widely ovate, 0.65—1.1 × 0.55—0.9 mm, pairs slightly unequal, white, often slightly upturned at acute to acuminate tip, short–papillate below tip on inner surface; stamens 4, fused to corolla tube at or slightly below sinuses between lobes; filaments ± cylindric aging flattened front–to–back, 0.35—0.6 mm long, whitish; anthers dorsifixed, dithecal, oblong to heart–shaped, 0.2—0.3 × 0.15—0.3 mm, light yellow, longitudinally dehiscent; pollen yellow; nectary disc 2–lobed (initially appearing as a circular disc but separating into 2 distinct semicircular ridges), ± flush with top of corolla tube, 0.15—0.4 mm diameter, green; pistil 1; ovary inferior, 2–lobed, lobes subspheric–oblong, ca. 0.8 × 1 × 0.6 mm, green, each half ellipsoid, with a light green, semicircular ridge at top, with upward–hooked bristles, 2–chambered, each chamber with 1 ovule; styles 2 (fused) ascending to erect, very short, 2–branched, base < 0.2 mm long, the branches unequal, 0.2—0.3 mm long; stigmas spherically capitate, whitish prior to pollination, papillate.
Fruit schizocarp, 2–chambered forming 2 dry, 1–seeded nutlets (mericarps) with fruit wall ± fused to seed coat; mericarp subspheroid to kidney–shaped, 2.2—2.8 × 1.9—2.3 mm, brownish, densely bristly with hooked prickles having swollen bases, the prickles to 0.6 mm long.
A. C. Gibson & B. A. Prigge