Galium obtusum Bigelow

Blunt-Leaved Bedstraw


CC = 5
CW = -3
MOC = 58

© SRTurner

Family - Rubiaceae

Habit - Perennial forb.

Galium_obtusum_habit.jpg Typical growth habit.

© SRTurner

Stems - Spreading to weakly ascending, clambering on other vegetation, usually well-branched, 4-sided, glabrous or sparsely pubescent with minute to short, straight, spreading hairs, these mostly restricted to the nodes.

Leaves - Whorled, usually 4 per node, usually spreading in orientation, simple, sessile, entire. Blades 5-23 mm long, 1-5 mm wide, narrowly elliptic, rounded or angled to a bluntly pointed tip, the midvein not extended into a point, angled or tapered at the base, the undersurface not glandular, glabrous or sparsely pubescent with minute to short, stout, stiff hairs along the midvein toward the base, the venation with only a single midvein visible, the margins glabrous or more commonly roughened with minute, ascending, spinelike outgrowths, usually somewhat curled under.

Galium_obtusum_leaves.jpg Stem and node.

© DETenaglia

Galium_obtusum_leaf2.jpg Leaves abaxial. Note single midvein.

© SRTurner

Inflorescence - Terminal and sometimes also axillary from the upper leaves, not pendent, positioned over the leaves, consisting of small (0.5-1.5 cm long), stalked clusters or less commonly panicles with 1 branchpoint, the branches, when present, loosely ascending.

Galium_obtusum_inflorescence.jpg Inflorescence.

© SRTurner

Flowers - Mostly few to several, the stalks 1-6 mm long. Calyces essentially absent. Corollas 1.5-2.5 mm long, 4-lobed, white. Stamens 4, attached in the corolla tube, the anthers exserted. Style 2-lobed, the stigmas 2, capitate. Ovary glabrous, inferior, 2-locular, the ovules 1 per locule.

Galium_obtusum_flowers2.jpg Flowers, with glabrous ovaries located just behind the corollas.

© SRTurner

Galium_obtusum_flowers.jpg Corollas.

© DETenaglia

Galium_obtusum_corollas.jpg Corollas are usually 4-lobed, but a few 5-lobed flowers are usually present.

© SRTurner

Fruits - Small, dry schizocarps 1.5-2.0 mm long, 3-4 mm wide, the surface glabrous, smooth, separating into two mericarps at maturity.

Flowering - May - July.

Habitat - Bottomland forests, swamps, sloughs, marshes, streambanks, fens, moist swales, ditches.

Origin - Native to U.S.

Lookalikes - Other species of Galium, especially G. tinctorium and G. circaezans.

Other info. - This little species can be found throughout Missouri. Its U.S. distribution is primarily within the Midwest, although it ranges to the Atlantic coast and into New England. It is considered a noxious weed in a few northeastern states. The plant can be identified by its moist to wet habitat, small white flowers, glabrous stems and ovaries, and leaves which are usually 4 at a node. When left untouched, the plant can grow into large mats. Missouri plants are assignable to ssp. obtusum. The other subspecies, ssp. filifolium (Wiegand) Puff, has narrower leaves and occurs primarily in Virginia and the Carolinas.

Galium is unusual in its apparent lack of interpetiolar stipules, in a family which is characterized by this feature. A school of thought holds that the structures at each node are actually opposite leaves alternating with greatly enlarged, leaflike stipules. Plants having whorls of 6 such structures are thought to represent a condition in which either the leaves or the stipules are divided to the base. In any case, the structures are not distinguishable morphologically, at least in mature stems.

Photographs taken at Taberville Prairie, MO., 6-7-03 (DETenaglia); also at Otter Slough Conservation Area, Stoddard County, MO, 5-20-2014 and 5-14-2016 (SRTurner).