Liatris

This is a distinctive, strictly North American genus, with very showy heads. All of our species are in cultivation. The long, slender, dense spikes of L. pycnostachya and L. spicata are perhaps best known, but larger-headed species, like L. aspera and L. scariosa, often abundant on jack pine and oak plains, can be very showy, especially vigorous plants with 75–100 or more heads (as when well nourished or thriving in a newly disturbed spot). Some species occasionally display a white-flowered form, with pale pink intermediates to be found where normal rose-purple flowers also occur.

The underground parts of L. punctata are elongate and slender, like a taproot (or horizontal like a rhizome), but our other species all have one to many stems arising from a perennial, rounded, eventually rather large structure usually called a corm, although it has no external evidence of leaves or nodes. This is a good device to aid survival after fire, for these are largely plants of wet or dry grasslands, prairies, and savannas, maintained by fire.

The terminal (or uppermost) head is the first to bloom in an inflorescence and hence tends to appear larger than the others at a given time. Characters of the phyllaries are best seen in fully mature heads. The distinctive mature phyllaries of L. aspera often have the broad scarious (but pinkish) apex neatly tucked beneath the firm part, making it appear to have a smooth, entire margin. At least, the margin is puckered and slightly tucked or folded.

1. Pappus bristles clearly plumose, the lateral branches more than 8 times as long as the diameter of the main bristle.

2. Corolla lobes glabrous; heads mostly 4–6-flowered; leaves up to 4 mm wide.

L. punctata

2. Corolla lobes long-hairy within; heads at least 10-flowered; leaves (at least the widest lower ones) usually at least 4 (rarely 2.5) mm wide.

3. Phyllaries with rounded or obtuse (rarely acute) tips, at most with a little apiculus, not spreading; stems glabrous.

L. cylindracea

3. Phyllaries with spreading, prolonged, acuminate tips; stems at least sparsely pubescent.

L. squarrosa

1. Pappus bristles strongly barbed, the lateral branches less than 5 times as long as the diameter of the main bristle.

4. Involucre ± cylindrical or conical, the heads with 5–10 flowers; inflorescence a long, cylindrical spike of dense sessile heads; moist to wet places.

5. Axis of inflorescence moderately to densely pilose with spreading-crinkly hairs; tips of most phyllaries tapered to a narrowly acute, often outcurved apex.

L. pycnostachya

5. Axis of inflorescence glabrous; tips of phyllaries rounded to obtuse, neither acute nor outcurved.

L. spicata

4. Involucre broadly rounded at the base, ± hemispheric, the heads with more than 10 flowers; inflorescence various; mostly dry habitats.

6. Middle phyllaries with a broad (ca. 1–2 mm) scarious margin apically, this often split or ± lacerate and usually puckered at the base or even tucked under the firmer portion of the phyllary; flowers ca. 14–28 (–30) per head; inflorescence elongate, spike-like, the heads all or mostly sessile or on pedicels shorter than the involucre.

L. aspera

6. Middle phyllaries with a very narrow scarious margin, this slightly toothed but scarcely if at all puckered or tucked; flowers ca. 40 or more per head; inflorescence ± racemose, the heads all or mostly on pedicels or bracted branches equaling or longer than the involucre.

L. scariosa

All species found in Liatris

Liatris asperaROUGH BLAZING-STAR 
Liatris cylindraceaCYLINDRICAL BLAZING-STAR 
Liatris punctataDOTTED BLAZING-STAR 
Liatris pycnostachyaPRAIRIE BLAZING-STAR 
Liatris scariosaNORTHERN BLAZING-STAR 
Liatris spicataMARSH BLAZING-STAR 
Liatris squarrosaPLAINS BLAZING-STAR 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 10, 2017. http://www.michiganflora.net/genus.aspx?id=Liatris.