Although widely reported across North America, this species was not mapped in Ky. by FNA 19 and there has been uncertainty about its identification and nomenclature. T. erythrospermum is close to officinale, but differs in its leaves lacerate (versus usually just lobed or toothed, at least in lower leaves), with petioles slightly winged distally (versus broadly winged); also, seeds are brick red, reddish-brown or purple (versus olive, olive-brown, tan or gray). It has been reported from Ky. (M), and several colls. have been noted with reddish seeds (from BULL, CALL, FAYE, FLEM, FRAN & SHEL). But most or all of these lack the distinctive "hooded appendage near the tip" of the inner involucral bracts (Cr); they may just be forms of officinale.