Pterocaulon pycnostachyum

(Michaux) Elliott

Sketch Bot. S. Carolina 2: 324. 1823.

Common names: Fox-tail or coastal blackroot
Basionym: Conyza pycnostachya Michaux Fl. Bor.-Amer. 2: 126. 1803
Synonyms: Pterocaulon undulatum C. Mohr
Treatment appears in FNA Volume 19. Treatment on page 476.

Plants 2–8 dm. Leaf blades lanceolate to obovate-lanceolate, oblong, or elliptic, 3–11 × 1–3(–3.5) cm, lengths mostly 2–7 times widths, margins usually dentate or denticulate, slightly repand, sometimes nearly entire. Heads in dense, usually continuous, rarely interrupted (then near bases), narrow, ± ovoid arrays (2–)3–8(–10) cm (usually single, sometimes with 1–2 basal branches). Involucres campanulate, 4–5 mm. Pistillate florets 23–44. Functionally staminate florets 6–10(–15). Cypselae 1–1.3 mm. 2n = 20.

Phenology: Flowering May–Jun.
Habitat: Sandy pinelands, sandy fields, depressions, ditches
Elevation: 0–20 m



Ala., Fla., Ga., Miss., N.C., S.C.


Differences between Pterocaulon pycnostachyum and P. alopecuroides (Lamarck) de Candolle, which is widespread in the West Indies and South America, are these: plants 50–70 cm high in P. pycnostachyum (versus 70–150 cm in P. alopecuroides), arrays of heads 4–8 cm (versus 3–17 cm) long, involucres 3.5–4 mm (versus 4.5–5 mm) high, and 6–15 (versus 1–3) functionally staminate florets (A. L. Cabrera and A. M. Ragonese 1978). In P. alopecuroides, the arrays of heads are almost always interrupted proximally, commonly producing sessile to subsessile branches. A count of functionally staminate florets provides a clear determinant for plants that might appear ambiguous in other features.

Selected References


Lower Taxa

... more about "Pterocaulon pycnostachyum"
Guy L. Nesom +
(Michaux) Elliott +
Conyza pycnostachya +
Fox-tail or coastal blackroot +
Ala. +, Fla. +, Ga. +, Miss. +, N.C. +  and S.C. +
0–20 m +
Sandy pinelands, sandy fields, depressions, ditches +
Flowering May–Jun. +
Sketch Bot. S. Carolina +
Pterocaulon undulatum +
Pterocaulon pycnostachyum +
Pterocaulon +
species +