5. Euonymus obovatus Nutt. (running strawberry bush)

E. americanus var. prostratus E.J. Palmer & Steyerm.

Pl. 351 k, l; Map 1508

Plants spreading or trailing shrubs, occasionally with a few ascending branches, but not climbing, the stems 0.3–1.2 m long, often rooting at the nodes. Twigs green, gray, or less commonly brownish purple, 4-angled but not winged. Leaves relatively thin and herbaceous, deciduous, subsessile, the petiole to 2 mm long. Leaf blades 3–7 cm long, 1.5–3.5 cm wide, obovate or less commonly elliptic, narrowed or tapered at the base, narrowed or tapered to a usually sharply pointed tip, the margins finely and usually sharply toothed. Inflorescences axillary clusters of 2 or 3 or solitary flowers. Sepals 5, 1.0–1.5 mm long. Petals 5, 2–3 mm long, 2–3 mm wide, broadly spatulate with a minute, stalklike base, greenish yellow and tinged with purple, the margins slightly irregular. Fruits 6–8 mm long, 2- or 3-lobed nearly their entire length, the valves strongly warty, pinkish purple. Seeds 1–6 per locule, 3–4 mm long. April–June.

Scattered in the Ozark and Ozark Border Divisions (eastern U.S. west to Missouri and Arkansas; Canada). Bases and ledges of sheltered bluffs and mesic upland forests; also rarely roadsides.

This species has a distinctive trailing growth habit. The stems spread out, producing many adventitious roots, but they never climb into trees. It is a shade-loving species, and flowers are produced sparingly. In most other respects, E. obovatus is very similar to E. americanus. In her monograph, Ma (2001) considered E. obovatus to be merely a growth form of E. americanus that is displayed under poor growing conditions, and she could find no clear way to separate the two taxa. There may be some merit to this assessment. However, in light of the tetraploid chromosome number and minor meiotic irregularities documented by Nath and Clay (1972) for E. americanus, further biosystematic investigation is called for. Many specimens of E. obovatus found along Ozark streams have characteristic obovate leaves, but a few have elliptical leaves like E. americanus. The lower stems on some specimens of E. americanus are trailing and rooting like E. obovatus. In general, E. americanus appears to produce more flowers and fruits than does E. obovatus.