Flora of North America species comparison

Liatris squarrulosa occurs across a range of habitats and exhibits much variation in habit, vestiture, and head size (involucral dimensions, numbers of florets, lengths of cypselae); it has not been possible in herbarium study to discern discrete geographic patterns. Plants in South Carolina (including the type of L. squarrulosa) are shorter, leaves and phyllaries are consistently glabrous or sparsely puberulent, involucres are (6–)7–10 × 6–10 mm, and mid to inner phyllaries usually are narrowly oblong. Westward and northward, plants are taller, leaves and phyllaries characteristically have more strongly elaborated vestiture (although considerable variation exists and glabrous plants are scattered nearly through the range), heads range larger, and phyllaries vary from broadly obovate to oblong-spatulate. An overview of head size is indicated by the following measurement samples: South Carolina—florets 12–16, cypselae (3–)3.5–4 mm; Georgia (including the type of L. earlei)—florets (11–)14–21, cypselae 4–5 mm; Alabama—florets 11–20, cypselae 3.5–5(–6) mm; Illinois (including the type of L. scabra) and Tennessee—florets 16–24, cypselae 3.5–5.5 mm; Louisiana—florets 16–21, cypselae 3.5–5 mm; Arkansas—florets (13–)21–26, cypselae 3.5–5 mm. Plants apparently disjunct in a cluster of north-central North Carolina counties have glabrous phyllaries and leaves, large heads, and the phyllaries are broad, more like plants to the west than those southward.

Populations in southwestern North Carolina (Cherokee, Clay, Macon, and Swain counties) and adjacent Tennessee, South Carolina, and Georgia appear to combine features of Liatris squarrulosa and L. scariosa var. scariosa. The plants are within the range of L. squarrulosa and disjunct from L. scariosa. The habit (large basal leaves, few cauline) is common to both taxa; heads are sessile to short-pedunculate (as in L. squarrulosa) and phyllaries are usually erect (the outer triangular and sometimes reflexing) and slightly broader than is characteristic of L. squarrulosa and often have a narrow hyaline border. These add further heterogeneity to the concept of L. squarrulosa, as circumscribed here; they may represent a separate evolutionary entity. The type of L. ruthii Alexander (an illegitimate name) from Tennessee is this form.

Hybrids:

Liatris species readily form hybrids. Named hybrids and their presumed parentals are:

Liatris ×boykinii Torrey & A. Gray; Lacinaria boykinii (Torrey & A. Gray) Kuntze—L. elegans × L. tenuifolia

Liatris ×creditonensis Gaiser—L. ligulistylis × L. squarrosa var. glabrata (known only from garden-grown plants)

Liatris ×deamii (Lunell) Shinners; Lacinaria deamii Lunell; Liatris scariosa (Linnaeus) Willdenow var. deamii (Lunell) Peattie—L. aspera? × L. ligulistylis?

Liatris ×fallacior (Lunell) Rydberg; Lacinaria fallacior Lunell—L. ligulistylis × L. punctata

Liatris ×freemaniana J. R. Allison—L. cylindracea × L. oligocephala

Liatris ×frostii Gaiser—L. aspera × L. pycnostachya

Liatris ×gladewitzii (Farwell) Shinners; Lacinaria gladewitzii Farwell—L. aspera × L. cylindracea

Liatris ×macdanieliana J. R. Allison—L. cylindracea × L. squarrosa

Liatris ×ridgwayi Standley—L. pycnostachya × L. squarrosa

Liatris ×spheroidea Michaux; Lacinaria aspera (Michaux) Greene var. spheroidea (Michaux) Alexander—L. aspera × L. ligulistylis? (fide L. O. Gaiser 1946)

Liatris ×steelei Gaiser—L. aspera × L. spicata

Liatris ×weaveri Shinners—L. aspera × L. punctata (known only from garden-grown plants)

(Discussion copyrighted by Flora of North America; reprinted with permission.)