1. Forsythia suspensa (Thunb.) Vahl (weeping forsythia)

Map 2094

Plants shrubs, 1–3 m tall, with perfect flowers. Main stems numerous, variously erect and wandlike to strongly arched and sometimes rooting at the tips, the bark light brown to tan, thin, the outer layer usually peeling in thin strips with age. Twigs relatively stout, green to reddish brown, becoming yellowish brown, glabrous, more or less 4-angled in cross-section, at least when young, with raised leaf scars and warty, oval, pale lenticels. Terminal buds ovoid to ellipsoid, with several, overlapping, sharply pointed scales, the axillary buds broadly ovoid, with scales that are bluntly to sharply pointed at the tips. Leaves opposite, short- to moderately petiolate. Leaf blades simple and at least in a few leaves ternately lobed and/or compound, 2–10 cm long, 1.5–5.0 cm wide, the blade or leaflets broadly ovate (in lobed leaves) to ovate or oblong-ovate, angled or tapered to the usually sharply pointed tip, rounded or angled at the base, the margins irregularly and sharply toothed (sometimes sparsely so), the surfaces medium green to yellowish green and glabrous. Inflorescences axillary, of solitary flowers or more commonly small clusters of 2 or 3(–5) flowers, produced from near the branch tip to older portions of branches, developing before the leaves, but often persisting as the leaves begin to expand; bracts absent, the flowers with slender stalks 3–6 mm long, not or only slightly fragrant. Calyces deeply 4-lobed, 4–7 mm long, the lobes oblong. Corollas deeply 4-lobed, 15–25 mm long, bell-shaped to more or less saucer shaped, the lobes narrowly oblong to strap-shaped, yellow (the 4–5 mm long tube often with orange stripes along the inner surface). Style 1–2 mm long, with a pair of ascending branches at the tip. Fruits very rare in North American plants, 2-locular, longitudinally dehiscent capsules, 15–25 mm long, narrowly ellipsoid to narrowly ovoid, beaked, brown with scattered, pale lenticels (seeds numerous, minute, narrowly winged). 2n=28. March–April.

Introduced, known thus far only from St. Louis County (native of Asia; introduced sporadically in mostly the eastern half of the U.S.). Mesic upland forests and banks of streams; also roadsides.

This taxon was first collected in 2004 by Rex Hill and the Botany Group of the Webster Groves Nature Study Society in a large wooded drainage where stem fragments probably washed down the slope from gardens in a subdivision along the adjacent ridge. Hardin (1974) and Chang et al., 1996) noted that each individual of Forsythia produces only one of two flower types, either with longer stamens and shorter styles or vice versa. This distylous behavior is correlated with an outcrossing breeding system. Hardin (1974) noted that unless individuals with both flower types are grown in proximity, they cannot effectively become pollinated, and that this might account for the rarity of fruits in North American cultivated and escaped plants.

Other commonly cultivated taxa in the genus include F. viridissima Lindl. and its hybrid with F. suspensa, F. ×intermedia Zabel. Numerous cultivars exist. Plantings may persist for years around old homesites, but escapes from cultivation appear to be rare, considering the popularity of these shrubs for landscaping. Forsythia viridissima differs from F. suspensa by having chambered pith throughout the younger branches (vs. hollow or with a few irregularly spaced cross-walls along the internodes and solid at the nodes), a somewhat more erect growth form, and in having only simple leaves. A specimen at William Jewell Collage collected in a forested area of Kansas City in 1971 may represent an escape, but the label data are ambiguous. Hybrid plants generally are intermediate, and tend to have chambered pith along the internodes and solid pith at the nodes. Pith characters can be confusing, with chambered, solid, and hollow types present in a single stem.