Standardized Common Name: Echinacea angustifolia; Echinacea pallida

Other Common Names: Purple Coneflower, Snakeroot; Kansas Snakeroot, Narrow-leaved Purple Coneflower (E. angustifolia); Pale Purple Coneflower (E. pallida)

Family: Asteraceae (Compositae)

Taxonomy: As usually defined, the genus Echinacea includes nine species of North American herbs. The most recent taxonomic treatment reduces these to only four. Echinacea angustifolia is treated as a variety of E. pallida, namely E. pallida var. angustifolia (DC.) Cronq. Although these two plants are extremely similar and are capable of interbreeding freely, the argument that they should be treated as belonging to a single species that would also include the former E. sanguinea Nutt., E. simulata McGregor and E. tennesseensis (Beadle) J. K. Small has not yet been widely accepted. Hybridization is common in Echinacea; E. pallida var. pallida may itself have originated as a tetraploid hybrid of two other species. Older literature often places the species of Echinacea in the genera Rudbeckia or Brauneria (the former being a related genus, and the latter being a superfluous synonym for Echinacea).

Description: Perennial herb, branched or unbranched, stems pubescent at least above with erect jointed hairs. Leaves alternate, petiolate below, sessile above, narrowly lanceolate to lanceolate or elliptical, the lower leaves 1–3(–4) cm broad; margins entire, pubescent; main veins 3 or 5, nearly parallel, unbranched; upper surface pubescent with erect jointed hairs. Inflorescence a capitulum (head), terminal, with receptacle nearly flat when young, conical to spherical at maturity, 15–30(–45) mm high; involucral bracts (phyllaries) usually in 2–3 series; receptacular bracts (paleae) usually longer than disk florets, with rigid awns. Ray florets ligulate, in 1 series, pale purple to pink or whitish, reflexed or spreading, usually sterile, pubescent, with toothed apex. Disk florets tubular; corollas 6–10 mm long, with bulbous base and 5 lobes, usually purplish; stamens 5; ovary 1, style 2-branched. Fruit a cypsela (achene with attached pappus), (2–)3–4(–6) mm long; those from disk florets quadrangular with pappus of 4 teeth or 1 large tooth; those from ray florets triangular, asymmetrical, usually with pappus of 3 teeth.

Echinacea angustifolia is on average a smaller plant than E. pallida, but the two species [or varieties] are most easily distinguished during flowering:

Parts in Commerce: Root with rhizome (aboveground parts could also be used)

Identification: Echinacea angustifolia and E. pallida have mostly identical root morphology:

• Cylindrical or gradually tapering, sometimes branching, sometimes spirally twisted
• Root 4–10 mm in diameter, uppermost (rhizome) portion to 15 mm
• More or less cylindrical when fresh; with deep longitudinal wrinkles when dried
• Pale brown, reddish to grayish or yellowish
• Fracture short and fibrous when dry; dried roots exposed to air may become tough and somewhat flexible
• In cross-section, shows thin brownish cork; thin cortex (to ca. 1 mm thick); cambial line; large xylem region, radially striated, with narrow strands of pale yellowish xylem separated by broader dark parenchyma rays (under high magnification of cut moist surfaces, discrete clusters of cells containing blackish pigment may appear elongated and fibrous)
• Rhizome cross-section similar, with circular, pale yellow to whitish pith at center
• Odor weak, aromatic, characteristic
• Taste weak, initially sweet, then bitter

Echinacea angustifolia produces a distinct tingling sensation when chewed due to the presence of alkylamides, which E. pallida does not. The cortex may be thicker in E. pallida (to 1.6 mm or so) and the dark pigmentation of the rays may be less distinct or absent in some material. Resin canals are present in both the cortex and xylem of E. pallida, versus the cortex alone of E. angustifolia. These canals are up to 0.15 mm in diameter, large enough to be seen in hand sections using a light microscope or when carefully cut segments of undried roots are examined with a dissecting microscope.

References:

Binns SE, Baum BR, Arnason JT. A taxonomic revision of Echinacea (Asteraceae: Heliantheae). Syst Bot. 2002;27:610–632.

McGregor RL. The taxonomy of the genus Echinacea (Compositae). Univ Kansas Sci Bull. 1968;68:113–142.

Wichtl M, ed. Herbal Drugs and Phytopharmaceuticals, 3^rd English ed. Stuttgart: medpharm Scientific Publishers and Boca Raton, FL: CRC Press; 2004:179–186.

World Health Organization. WHO Monographs on Selected Medicinal Plants. Vol. 1 Geneva: World Health Organization; 1999–2002:125–135.

Figure 22: a–c, Echinacea pallida head, leaf and root cross-section; d, E. angustifolia root cross-section.