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compass plant

roughleaf rosinweed, roughstem rosinweed, starry rosinweed

Habit Plants scapiform, (40–)100–300 cm; taprooted. Plants caulescent, 30–250 cm; fibrous rooted.
Stems

terete, hirsute, hispid, or scabrous.

terete, scabrous, hispid, or hirsute.

Leaves

basal persistent, petiolate or sessile;

cauline petiolate or sessile;

blades lanceolate, linear, ovate, or rhombic, 4–60 × 1–30 cm, usually (proximal) 1–2-pinnately lobed, bases attenuate to truncate, ultimate margins unevenly toothed or entire, apices acute, faces hirsute, hispid, or scabrous.

basal persistent or caducous, petiolate;

cauline alternate or opposite, petiolate or sessile;

blades lanceolate to ovate, 2–22 × 0.5–8 cm, bases attenuate to round, margins coarsely dentate or entire, apices acuminate to acute, faces scabrous, hispid, or hirsute.

Ray florets

27–38;

corollas yellow.

12–30+;

corollas yellow.

Disc florets

100–275;

corollas yellow.

100–175;

corollas yellow.

Phyllaries

25–45 in 2–3 series, outer reflexed or appressed, apices acuminate to caudate, abaxial faces hispid to scabrous, ± stipitate-glandular.

18–37 in 2–4 series, outer appressed or reflexed, apices acute, abaxial faces scabrous.

Cypselae

10–18 × 6–12 mm;

pappi 1–3 mm.

10–17 × 7–15 mm;

pappi 2–5 mm.

2n

= 14.

Silphium laciniatum

Silphium radula

Phenology Flowering summer–early fall.
Habitat Prairies, open, disturbed sites
Elevation 50–600 m (200–2000 ft)
Distribution
from FNA
AL; AR; IA; IL; IN; KS; KY; LA; MI; MN; MO; MS; NE; NM; NY; OH; OK; PA; SD; TN; TX; WI; ON
[WildflowerSearch map]
[BONAP county map]
from FNA
AR; KS; LA; MO; OK; TX
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 2 (2 in the flora).

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

Key
1. Basal leaves caducous; ray florets 20–30+
var. radula
1. Basal leaves persistent; ray florets 12–18
var. gracile
Source FNA vol. 21, p. 78. FNA vol. 21, p. 80.
Parent taxa Asteraceae > tribe Heliantheae > subtribe Ecliptinae > Silphium Asteraceae > tribe Heliantheae > subtribe Ecliptinae > Silphium
Sibling taxa
S. albiflorum, S. asteriscus, S. brachiatum, S. compositum, S. glutinosum, S. integrifolium, S. mohrii, S. perfoliatum, S. radula, S. terebinthinaceum, S. wasiotense
S. albiflorum, S. asteriscus, S. brachiatum, S. compositum, S. glutinosum, S. integrifolium, S. laciniatum, S. mohrii, S. perfoliatum, S. terebinthinaceum, S. wasiotense
Subordinate taxa
S. radula var. gracile, S. radula var. radula
Synonyms S. laciniatum var. robinsonii
Name authority Linnaeus: Sp. Pl. 2: 919. (1753) Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 341. (1840)
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