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Published In: Genera Plantarum 2: 542. 1791. (Gen. Pl.) Name publication detail

Project Name Data (Last Modified On 8/11/2017)
Acceptance : Accepted
Project Data     (Last Modified On 8/10/2009)


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56. Liatris Gaertn. ex Schreb. (blazing star)

Plants perennial, the rootstock an ovoid to depressed-globose corm, this usually covered with the persistent, brown, fibrous remains of old leaf bases (except in L. punctata, with an elongate rootstock). Stems solitary to several, erect or ascending. Leaves alternate but sometimes so numerous and dense as to appear indefinitely whorled, the basal and lower stem leaves short-petiolate, grading abruptly into the sessile or very short-petiolate stem leaves; the basal leaves often present at flowering, these and the adjacent lowermost stem leaves the largest on the plant. Blades of the basal leaves usually oblanceolate to narrowly elliptic, grading abruptly into the linear or less commonly narrowly elliptic to narrowly oblong stem leaves, all tapered at the base, usually tapered to a sharply pointed tip, the margins entire, the surfaces variously short-hairy to glabrous or nearly so, often also gland-dotted, with 1 or 3(5) main veins. Inflorescences unbranched terminal spikes or spikelike racemes (sometimes somewhat branched elsewhere), sometimes leafy and the lowermost heads then appearing axillary. Heads with 4–80 disc florets. Involucre cylindrical to broadly cup-shaped or bell-shaped, the bracts mostly 18–40, in usually 3 to several unequal, overlapping series, the bracts lanceolate to broadly ovate, tapered (often abruptly so) to a sharply pointed tip, glabrous or short-hairy, often also glandular. Receptacle flat or nearly so. Corollas pink to purple, rarely white, often sparsely glandular on the outer surface, sometimes hairy on the inner surface. Pappus of 12–40 bristles, these minutely barbed (the short barbs mostly 0.1–0.3 mm long) or plumose (the feathery barbs mostly 0.5–1.0 mm long). Fruits (8–)10-nerved or ribbed, slightly wedge-shaped in profile (usually slightly and unevenly tapered at the base) to nearly linear, usually minutely hairy and glandular, brown to dark brown. About 45 species, U.S., Canada, Mexico, Caribbean Islands.

Liatris species are among the showier plants to grace native wildflower gardens. A number of species are in cultivation (Dress, 1959), and most of the Missouri taxa can be purchased at native plant specialty nurseries in the state. Liatris spicata has become more widely available at home supply centers and general plant nurseries and also is coming into broader use as a cut flower at florists and even grocery stores. In the garden, these plants attract a host of animals, including a wide variety of insects visiting the flowers and birds feeding on the achenes, but the sweet, thickened rootstocks are a magnet for voles and other herbivorous mammals. Rootstocks of various species also were consumed raw or baked by early settlers and by Native Americans. Various tribes also used some Liatris species medicinally as a general analgesic, to settle upset stomachs, for urinary tract problems, and in poultices to ease skin inflammations, among other uses (Moerman, 1998). The common name snakeroot, applied to some species, apparently is in reference to a belief in their efficacy in the treatment of snakebite. Horses sometimes were fed a decoction of the rootstocks as a stimulant before races (Moerman, 1998).

Liatris is a taxonomically difficult genus that requires much further research. For some of the complexes, species limits still are not well understood, and the impact of hybridization and polyploidy upon the recognition of species has not been well studied for most of our taxa. In perhaps the only detailed study of hybridization in the group, Levin (1968) examined a mixed population of L. aspera, L. cylindracea, L. ligulistylis (probably actually L. scariosa), and L. spicata in northern Illinois, documenting an extensive swarm of mostly fertile hybrids. Steyermark (1963) noted that the last monographer of the genus, Lulu O. Gaiser (1946), did not examine specimens from any of the herbaria having large holdings of Missouri materials.


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1 1. Pappus bristles plumose

2 2. Leaves mostly with 3(5) main veins; heads with 10–60 disc florets; corolla lobes hairy on the inner surface

3 3. Involucre with the outer series of bracts not appearing noticeably longer than the other series, the bracts appressed or strongly ascending, broadly rounded or broadly angled to a bluntly pointed tip, or more commonly short-tapered to an abrupt, sharp point at the tip ... 2. L. CYLINDRACEA

Liatris cylindracea
4 3. Involucre with the outer series of bracts usually appearing noticeably longer than the other series (especially on the terminal head), the bracts abruptly spreading to recurved above the basal portion, mostly long-tapered to a sharply pointed tip ... 8. L. SQUARROSA

Liatris squarrosa
5 2. Leaves mostly with 1 main vein; heads with 3–7 disc florets; corolla lobes glabrous; species difficult to distinguish

6 4. Rootstock a corm, more or less globose; leaves green, glabrous; involucre 7–12 mm long ... 3. L. MUCRONATA

Liatris mucronata
7 4. Rootstock more or less a thickened, elongate taproot, vertical or occasionally somewhat spreading; leaves grayish green, at least some of them hairy along the margins (note that the hairs break off with age, leaving minute, stubby bases); involucre 10–14 mm long ... 4. L. PUNCTATA

Liatris punctata
8 1. Pappus bristles merely barbed

9 5. Heads with (3)4–9(–14) disc florets; involucre narrowly cup-shaped to nearly cylindrical; basal and lower stem leaves (and often most other stem leaves) with 3 or 5 main veins

10 6. Involucral bracts tapered to long, sharply pointed tips, these spreading or recurved ... 5. L. PYCNOSTACHYA

Liatris pycnostachya
11 6. Involucral bracts rounded or broadly angled to a bluntly pointed tip, appressed ... 7. L. SPICATA

Liatris spicata
12 5. Heads with (11–)14–80 disc florets; involucre broadly cup-shaped to bell-shaped; leaves with 1 main vein; species difficult to distinguish

13 7. Involucral bracts mostly with broad, thin, pale to transparent margins, these sometimes strongly purplish-tinged, appearing irregularly torn or strongly uneven (irregularly wavy or scalloped), the main body appearing swollen or pouched ... 1. L. ASPERA

Liatris aspera
14 7. Involucral bracts with green (unmodified) or narrow, thin, pale to transparent margins, these sometimes strongly purplish-tinged, entire or sometimes appearing wavy or shallowly scalloped (sometimes also minutely irregular), the main body sometimes recurved at the tip but appearing not or only slightly swollen or pouched

15 8. Heads with 28–80 disc florets, relatively long-stalked, the stalks 12–40(–150) mm long, often with several small bracts; all or nearly all of the involucral bracts erect or ascending, the lowermost sometimes spreading or reflexed ... 6. L. SCARIOSA

Liatris scariosa
16 8. Heads with 11–26(–28) disc florets, sessile or relatively short-stalked, the stalks to 15 mm long, the longer ones sometimes with a few small bracts; nearly all of the involucral bracts with the tip spreading or reflexed, only the innermost series usually ascending ... 9. L. SQUARRULOSA Liatris squarrulosa
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