1. Cymbalaria muralis P. Gaertn., B. Mey. & Scherb. (kenilworth ivy)

Pl. 481 h, i; Map 2202

Plants annuals, with fibrous roots (young plants may also have small taproots), terrestrial. Stems 10–40 cm long, prostrate or loosely spreading, sometimes twining and thus climbing on surrounding vegetation, rooting at the nodes, glabrous. Leaves alternate, long-petiolate, the petiole bases not expanded. Leaf blades 1.0–2.5 cm long, 10–35 mm wide, kidney-shaped to nearly circular in outline, shallowly and palmately 5(–9)-lobed or coarsely toothed, the lobes or teeth mostly short-tapered to a bluntly or sharply pointed tip, truncate to more commonly cordate at the base, the margins otherwise entire, sometimes with a narrow reddish marginal line, the venation palmate with as many main veins as lobes, glabrous. Inflorescences axillary, of solitary flowers, the flower stalks 10–35 mm long at flowering, becoming elongated to 22–70 mm at fruiting; bractlets absent. Flowers perfect. Calyces 1.5–2.0 mm long at flowering, becoming enlarged to 2–3 mm at fruiting, deeply 5-lobed nearly to the base, the lobes slightly unequal in length, linear to narrowly lanceolate, mostly sharply pointed at the tip, glabrous. Corollas 8–11 mm long (including the spur), bilabiate, 5-lobed, glabrous, the tube shorter than to about as long as the lobes, the tube bluish purple to purplish blue, the lobes similar, but the throat with white and yellow markings, the tube with a short, blunt spur at the base (this positioned between the lower 2 calyx lobes), the throat mostly closed by the strongly convex base of the lower lip, the upper lip more or less straight to somewhat arched outward, the lower lip with the lobes spreading to strongly arched. Fertile stamens 4, the filaments of 2 lengths, not exserted, the anther sacs spreading; staminodes absent. Style 1, not exserted, the stigma capitate, unlobed. Fruits capsules, 2.5–4.0 mm long, globose, glabrous, the 2 locules equal in size, dehiscent by pores near the tip, each locule with 1 pore, the valves eventually separating completely with age. Seeds numerous, 0.7–1.0 mm long, ellipsoid to nearly circular in profile, not flattened, the surface dark brown, with a network of usually mostly longitudinal, coarse ridges. 2n=14. May–October.

Introduced, known thus far only from historical collections from Marion and St. Louis Counties (native of Europe, Asia; introduced widely but sporadically in the U.S., Canada). Banks of rivers; also roadsides and open, disturbed areas.

Kenilworth ivy is an attractive groundcover that is widely cultivated in gardens and rarely escapes into natural plant communities. Sutton (1988) recognized three subspecies within the native range based on differences in pubescence density and flower stalk lengths, but noted that the species is morphologically variable and occurs in a number of different habitats. Although the Missouri materials all appear to correspond to the glabrous ssp. muralis, it does not seem prudent to attempt to classify the North American plants below the species level.