1. Gymnocladus dioica (L.) K. Koch (Kentucky coffee tree)

G. canadensis Lam.

Map 1694, Pl. 385 j–l

Plants trees 10–20 m tall, usually incompletely dioecious, sometimes colonial from root suckers, unarmed, the bark shallowly grooved, silvery gray, often reddish-tinged, developing small, scaly ridges and becoming dark gray on older trunks, the branches not producing short shoots but the leaves sometimes tending to be clustered toward the branch tips, the twigs stout, the winter buds inconspicuous and strongly sunken into the twig; root nodules absent. Leaves appearing before the flowers, the petiole 10–20 cm long, the blade 30–90 cm long, 2 times pinnately compound, with 4–7 pairs of pinnae, each with 4–6 pairs of alternate leaflets, the lowermost pair of pinnae sometimes replaced with a pair of large leaflets. Stipules inconspicuous and scalelike, shed early. Leaflets 2–9 cm long, 1.5–5.0 cm wide, ovate to broadly elliptic, rounded to angled at the base, short-tapered or tapered to a sharply pointed tip, the margins entire and inconspicuously short-hairy, the upper surface glabrous, the undersurface finely hairy. Inflorescences racemes or more commonly narrow, racemose panicles, mostly appearing terminal, 14–20 cm long, ascending to spreading; some trees with all staminate or all pistillate inflorescences, but often otherwise with some inflorescences having mixed imperfect and perfect flowers. Flower stalks 10–35 mm long. Flowers perigynous, more or less actinomorphic, fragrant. Hypanthium 8–12 mm long, tubular to narrowly funnelform, densely hairy. Calyces of 5 sepals, these subequal, 4–7 mm long, narrowly oblong-elliptic, sharply pointed at the tip, moderately to densely hairy, not closing the flower in bud. Petals (3–)5, 4–10 mm long, 1.5–2.5 mm wide, greenish white, densely woolly. Stamens 10, unequal in 2 alternating long and short series, the filaments not fused, hairy at the base, the anthers 1.2–1.6 mm long, attached toward the midpoint. Style short, relatively straight, the stigma oblique. Fruits legumes, 9–15 cm long, 2–5 cm wide, 1.0–1.5 cm thick, more or less oblong, straight or slightly curved, rounded or short-angled at the base and sometimes with a short stalk to 0.5 cm long, abruptly short-tapered to a usually sharply pointed tip, 1–4-seeded, the valves velvety when young, becoming woody and glabrous, persistent into the winter, the valves dehiscing with age along the ventral suture, seeds with a stout attachment and embedded in a green, jellylike pulp. Seeds 15–20 mm in diameter, ovate to circular, somewhat flattened but turgid, dark reddish brown, hard, shiny; pleurogram absent. 2n=28. May–June.

Scattered, but nowhere common, nearly throughout the state (eastern U.S. west to North Dakota and Texas; Canada). Bottomland forests, mesic upland forests, banks of streams and rivers, and bases of bluffs.

Although widely distributed, G. dioica is relatively infrequently encountered and apparently absent from many areas. It frequently occurs as a single tree or small colony in especially favorable sites, some of these possibly prehistoric settlements or campsites (Lee, 1976). For a discussion of dispersal problems for this and other species, see the treatment of Gleditsia triacanthos above.

The seeds are said to have been roasted and used as a substitute for coffee in the Revolutionary War and by the early settlers, but Thomas Nuttall (1821) reported that they were a poor substitute compared to chicory. The pulp, fresh seeds, and foliage are considered somewhat poisonous, apparently because of a variety of saponins, terpenoids, alkaloids, and unusual amino acids present in various parts of the plants (Burrows and Tyrl, 2001). Gymnocladus dioica is sometimes planted as a specimen tree, growing best in deep, rich soils with good drainage. It is one of the last trees to develop new leaves in the spring and is among the first to shed them in the autumn. The leaves turn a dusty yellow color in the fall. Some of the fruits are retained on the branches through the winter.

This generic name traditionally has been treated as feminine. However, according to the International Code of Botanical Nomenclature (Greuter et al., 1999) generic names formed from two words take the gender of the second word, in this case cladus, which is masculine (Robertson and Lee, 1976; Lee, 1976). Harriman (1998) submitted a proposal to conserve the generic name as masculine, but this became bogged down during discussion in the Committee for Spermatophyta and has yet to be resolved. Thus the species is spelled G. dioicus and G. dioica in various recent floristic and taxonomic treatments (Gleason and Cronquist, 1991; Isely, 1998).