2. Galium aparine L. (cleavers, goose grass, annual bedstraw)

Pl. 545 a, b; Map 2536

Plants annual. Stems 10–100 cm long usually weak, spreading to loosely ascending or clambering, often few- to several-branched (small plants may be unbranched), minutely roughened with minute, prickly, downward-curved hairs on and sometimes also between the angles, otherwise glabrous or only sparsely pubescent with short hairs. Leaves 6–8(10) per node, generally spreading or somewhat ascending in orientation. Leaf blades 8–60 mm long, 1–5 mm wide, narrowly oblanceolate, short-tapered to a sharply pointed tip, the midvein usually extended into a short, sharp point, angled or tapered at the base, not glandular on the undersurface, with only the midvein visible, the margins with minute, stiff, prickly hairs and usually somewhat curved under. Inflorescences axillary, occurrring mostly at nodes above the stem midpoint, not pendant, positioned over the leaves, consisting of small clusters or fascicles (occasionally reduced to solitary flowers), these sometimes grouped into small panicles with mostly 1 or 2 branch points and relatively short, ascending branches. Flowers relatively few, the stalks absent or to 1 mm long at flowering, becoming elongated to as much as 8 mm at fruiting. Corollas 1.0–1.2 mm long, 4-lobed, white. Fruits 2–3 mm long, 3.5–5.5 mm wide, the surface densely pubescent with hooked hairs 0.5–0.8 mm long. 2n=22, 42, 44, 63, 64, 65, 66, 86. April–July.

Scattered to common throughout the state (U.S. [including Alaska]; Canada, Greenland, Europe, Asia, Africa; introduced in the southern hemisphere). Bottomland forests, mesic upland forests, banks of streams and rivers, margins of ponds, lakes, and oxbows, bottomland prairies, marshes, sloughs, and occasionally glades; also pastures, ditches, old mines, gardens, lawns, railroads, roadsides, and disturbed areas.

Steyermark (1963) commented on use of the fruits of this plant as a coffee substitute. Native Americans used the plant medicinally for renal, urinary, and dermatological problems (including treatment for poison ivy rashes), and also as an antihemorrhagic, diuretic, and love potion (Moerman, 1998). Galium aparine is also a minor crop weed that impacts mainly crop species harvested relatively early in the growing season, such as winter wheat crops and some members of the mustard family. The status of the species in North America has been a source of controversy. R. J. Moore (1975) in his study of the taxon in Canada, suggested that although it apparently was native in mostly coastal portions of northwestern North America, most or all of the inland populations represented an introduction of the species from Europe by early settlers as a contaminant in crop seeds. In the Midwest, Deam (1940) considered it to be native in Indiana and Steyermark (1963) also treated it as native in Missouri. The oldest herbarium specimens collected in the state, which date from the 1860s, were collected from natural habitats. Thus, although it is not possible to confirm the status of the taxon with certainty, there is no compelling evidence to support that it is not native to the region.

One clue to the identification of Galium aparine is its roughened surfaces: not only the fruits but the entire plant will adhere to clothing or animal hair. The stickiness of the leaves and stems is due to tiny downward-curved prickles on their surfaces. These prickles are single-celled, hardened protuberances of the plant epidermis. They adhere to the stems of other plants and even to each other, so the plants often form extensive tangles, which disappear by late summer. Some other species (notably G. asprellum) are similarly sticky.

Smaller-leaved plants from throughout the range of this species were once treated as G. vaillantii DC. or G. aparine var. vaillantii (DC.) Koch, but this variety has not been recognized taxonomically since the early twentieth century. Even Steyermark (1963) declined to separate it, suggesting instead that it represented plants growing in poorer soils in drier, more exposed habitats.

Galium spurium L. of Eurasia and Africa is similar to G. aparine. Their alleged (Voss, 1996) distinctions, although clearly stated in keys can be rather subtle to diagnose on living plants. Flowers are 0.8–1.3 mm in diameter and greenish yellow in G. spurium, vs. 1.5–1.8 mm in diameter and white in G. aparine. Fruits are 2–3 mm in diameter in G. spurium, vs. 3–5 mm in diameter in G. aparine. Chromosome numbers also are different, 2n=20, 40 in G. spurium, vs. 2n= mostly some multiple of 22 in G. aparine. Galium spurium has been reported from Canada by Moore (1975), but in the United States only a few reports from western states exist and these require verification. Although Moore suggested that it might be present in Missouri, the specimens so far collected from Missouri under the name G. aparine have been reviewed during the present study for clear signs of falsity, which has not been found. In the past, the name G. spurium has been applied in error to some North American plants of G. aparine, which has further confused the situation. For the technically minded, the separation of these two species is touched on by Verdcourt (1976) and was also discussed by Moore (1975) and Malik and Vanden Born (1988).