3. Liatris mucronata DC. (narrow-leaved gayfeather)
Pl. 269 i–j; Map
1123
Rootstock a more
or less globose corm. Stems 20–90 cm long, glabrous. Basal and adjacent lower
stem leaves sessile to short-petiolate, the blades 7–15 cm long, 1–4 mm wide,
linear, the narrow, light margins occasionally curled under, the surfaces
glabrous, green, with 3(5) main veins, grading toward the stem tip to shorter
leaves, these mostly sessile, 1.5–12.0 cm long, linear. Inflorescences elongate
spikes, the heads densely spaced (the axis mostly not visible between heads),
sessile or nearly so, with 1 basal bract. Heads with 3–6 disc florets, the
terminal head sometimes slightly longer than the others. Involucre 7–12 mm long,
narrowly cup-shaped to nearly cylindrical, with 4–6 unequal, overlapping series
of bracts (the outer series appearing somewhat shorter). Involucral bracts
broadly lanceolate to narrowly oblong-obovate, tapered to a sharply pointed,
ascending to somewhat spreading tip, mostly with narrow, thin, pale to
transparent margins, these sometimes slightly to strongly purplish-tinged, more
or less entire but sometimes cobwebby-hairy, the main body appearing flat below
the tip. Corollas 9–11 mm long, glabrous or the tube sparsely hairy on the
inner surface toward the base. Pappus bristles plumose. Fruits 5.5–7.5 mm long.
July–October.
Uncommon in the
western portion of the Ozark Division, mostly in the watershed of the White
River and its tributaries (Kansas and Missouri south to Texas and possibly
Louisiana). Glades and ledges and tops of bluffs, on limestone and dolomite
substrates.
The aboveground
portions of plants of L. mucronata and L. punctata can be
surprisingly difficult to distinguish. In Missouri, where the ranges of the two
do not overlap, it has proven easier to separate specimens lacking rootstocks
by geography than morphology. The combination L. punctata var. mucronata
(DC.) B.L. Turner is available if future research should show that the apparent
morphological differences in rootstock are due more to environmental variation
than to taxonomy. One qualitative difference between them is that in L.
mucronata the leaves are described as green, relatively soft-herbaceous,
mostly arched or curved outward, and glabrous, whereas in L. punctata
the leaves are said to be relatively thick and leathery, mostly straight or the
largest ones only slightly curved outward, and at least some of them hairy
along the margins (note that the hairs break off with age, leaving minute,
stubby bases).
These plants are
part of a polyploid complex that is widespread in the center of the United
States and needs more intensive biosystematic study. A recent segregate in this
complex from northern Texas and Oklahoma was described as L. aestivalis
G.L. Nesom & O’Kennon and differs from typical L. mucronata in its
fewer longer involucral bracts, slightly more pronounced leaf venation, and
earlier flowering period, among other subtle characters. However, Nesom and
O’Kennon (2001) noted that some plants attributed to L. mucronata from
northern Arkansas, southern Missouri, and adjacent Kansas may represent an
undescribed taxon more closely related to L. aestivalis than to L.
mucronata in the strict sense. Further studies of population-level
variation and cytology are needed.