This is the true bittersweet of medicine, and should not be confused with Celastrus scandens which is also called bittersweet. This species is more or less frequent in the lake area and is practically confined to it although it is reported from 6 of the southern counties. It is found in swamps, bogs, and low woods and along low roadsides. Authors say it is adventive from Europe but all of our early authors found it and its habitat suggests that it is native. It is, no doubt, native in Indiana. This species varies greatly in the amount of pubescence of the branchlets, varying from almost glabrous to rather densely pubescent but the pubescence not quite dense and long enough to make our specimens belong to the pubescent variety. The young branchlets are used in medicine. White-flowered forms are found occasionally.
Rhizomatous perennial, shrubby below, climbing or scrambling to 1-3 m, moderately short-hairy to glabrous; lvs petiolate, some simple and with rather broadly ovate-subcordate blade 2.5-8 נ1.5-5 cm, others with a pair of smaller basal lobes or lfls; peduncles 1.5-4 cm, 10-25-fld, the infl 3-8 cm wide, jointed, bractless, often subdichotomously branched; cor light blue or violet, the lobes 5-9 mm (each with 2 shiny green basal spots), soon reflexed; anthers conspicuous, yellow; fr poisonous, bright red, 8-11 mm; 2n=24, 48, 72. Thickets, clearings, and open woods, often in moist soil; native of Eurasia, naturalized throughout our range.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.