1. Tiarella cordifolia Linnaeus, Sp. Pl. 1: 405. 1753.
Heart-leaf foamflower, tiarelle cordifoliée
Tiarella cordifolia var. austrina Lakela; T. cordifolia var. bracteata Farwell; T. cordifolia subsp. collina Wherry; T. macrophylla Small; T. wherryi Lakela
Flowering stems 15-40 cm. Leaves simple; cauline leaves absent or 1; petiole 0.2-2 dm; blade 3-13 × 3-10 cm. Inflorescences racemes, 15-50-flowered, 4-40 × 1-2 cm. Pedicels subtended by finely dissected bracts, 0.1-0.8 cm, glandular-stipitate. Flowers: hypanthium campanulate, 3-6 mm, glandular-stipitate; perianth radially symmetric; sepals spreading at anthesis, reflexed in fruit, 1.5-3.5 × 0.5-1 mm; petals caducous, spreading, oblanceolate to elliptic, unlobed, 0.6-1 × 3-4.5 mm, base clawed, apex 3-toothed; stamens equal, 2-6 mm; anthers oval, 0.3-0.5 mm. Capsules 0.5-1.1 cm. Seeds 4-15, ellipsoid, 0.9-1 × 0.4-0.7 mm. 2n = 14.
Flowering Mar-Jul; fruiting Apr-Sep. Open and shady, dry to swampy deciduous woods, along streams; 40-800 m; N.B., N.S., Ont., Que.; Ala., Conn., Ga., Ky., Maine, Md., Mass., Mich., Minn., Miss., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Vt., Va., W.Va., Wis.
Tiarella macrophylla was described from Tyron Mountain, North Carolina; the specimen consists of basal leaves of Heuchera villosa and racemes of T. cordifolia. Tiarella wherryi and T. cordifolia have been differentiated primarily on the basis of lack of stolons in T. wherryi. Such plants grow in mixed populations and it has been impossible to differentiate taxa on the basis of herbarium specimens. It is also thought that the differences between the taxa might be a result of altitudinal variation in habitat. Attempts by Lakela to distinguish var. cordifolia and var. austrina on the basis of leaf dimensions and marginal dentation have been thwarted by continuous variation in these characteristics.