Flora of North America species comparison

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Tetradymia axillaris

catclaw horsebrush, cottonthorn, longspine horsebrush
Habit Shrubs, 50–150 cm.
Stems

1–5+, erect or spreading, spiny, evenly pannose.
Leaves

primaries forming straight, ± squarrose spines, 10–50 mm;

secondaries filiform to clavate, 2–12(–20) mm, sparsely arachnose or glabrous.
Peduncles

4–15 mm.
Involucres

turbinate to campanulate, 7–9 mm.
Florets

5–7;

corollas pale yellow, 7.5–9 mm.
Phyllaries

5, ovate.
Heads

1–3 (in axils of spines).
Cypselae

4.5–5.5 mm, densely pilose (hairs 6–14 mm);

pappi of ca. 25, subulate to setiform scales 6–7.5 mm.

Tetradymia axillaris
Distribution
from FNA
CA; NV; UT
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 2 (2 in the flora).

The two varieties of Tetradymia axillaris are partially sympatric and intergrade in areas of overlap.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Peduncles and phyllaries pannose to tomentose; hairs of cypselae 9–14 mm
var. longispina
1. Peduncles and phyllaries glabrous; hairs of cypselae 6–8(–10) mm
var. axillaris
Source FNA vol. 20, p. 632.
Parent taxa Asteraceae > tribe Senecioneae > Tetradymia
Sibling taxa
T. argyraea, T. canescens, T. comosa, T. filifolia, T. glabrata, T. nuttallii, T. spinosa, T. stenolepis, T. tetrameres
Subordinate taxa
T. axillaris var. axillaris, T. axillaris var. longispina
Name authority A. Nelson: Bot. Gaz. 37: 277. (1904)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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