Key to Gamochaeta

View taxon page for Gamochaeta

(For a list of species in Gamochaeta, use the above link.)

Jepson Manual glossary definitions can be seen by moving your cursor over words underlined with dots.

1. Leaf faces contrasting in color, adaxially ± glabrous to ± cobwebby-tomentose, abaxially white-felty 

tomentose 

Covered with densely interwoven, generally matted hairs.

2. Adaxial 

leaf 

Organ arising from a stem, generally composed of a stalk (petiole) and a flat, expanded, green, photosynthetic area (blade); distinguished from a leaflet by the presence in its axil of a bud, branch, thorn, or flower; sometimes with lateral, basal appendages (stipules); either simple (toothed, lobed, or dissected but not divided into leaflets) or compound (divided into leaflets).

face ± glabrous; 

involucre 

Group of bracts more or less held together as a unit, subtending a flower, fruit (acorn cup), or inflorescence.

± purple, 2.5–3 mm, base glabrous; outer phyllaries elliptic-obovate to widely ovate-elliptic, rounded to 

obtuse 

Having a short-tapered, blunt tip or base, the sides convex or straight and converging at more than a right angle.

; disk flowers 2–3; fruit 0.5–0.6 mm ..... G. coarctata

2' Adaxial leaf face ± sparsely cobwebby-tomentose; involucre ± brown, 3–5 mm, embedded in woolly hairs, base often sparsely cobwebby; outer phyllaries and flattened tips of inner dark or ± green-brown, 

ovate 

Egg-shaped (i.e., widest below the middle) in two dimensions (i.e., in one plane), as a leaf.

to ovate-lanceolate or widely ovate-triangular, truncate-rounded or 

acute 

Having a short-tapered, sharp tip, the sides convex or straight and converging at less than a right angle.

to 

acuminate 

Having a long-tapered, sharp tip, the sides concave.

; disk flowers (3)4–6; fruit 0.5–0.8 mm

3. Involucre 3–3.5 mm; 

head 

1. A dense, often spheric inflorescence of sessile or subsessile flowers.
2. In Asteraceae and some other groups, a head-like inflorescence is one in which sessile or subsessile inflorescence units (e.g., heads in Asteraceae, umbels enclosed by involucres in Eriogonum), instead of individual flowers, are attached in a short dense cluster without an evident axis or branches.

clusters 10–12 mm wide (pressed); outer phyllaries ovate to ovate-lanceolate; fruit 0.5–0.6 mm ..... G. argyrinea

3' Involucre 4.5–5 mm; head clusters 12–18 mm wide (pressed); outer phyllaries widely ovate-triangular; fruit 0.7–0.8 mm ..... G. ustulata

1' Leaf faces not or weakly contrasting in color, ± green or gray-green, loosely tomentose or cobwebby, sometimes ± felty, sometimes adaxially ± glabrous in Gamochaeta stagnalis

4. Basal and proximal cauline leaves 4–16 mm wide; bracts among heads, cauline leaves oblanceolate to spoon-shaped, at least proximal bracts surpassing clusters of heads ..... G. pensylvanica

4' Basal and proximal cauline leaves 2–9 mm wide; bracts among heads, mid to distal cauline leaves generally 

linear 

Elongate, with nearly parallel sides; narrower than elliptic or oblong.

to ± oblanceolate, bracts surpassing heads or not

5. Mid and distal cauline leaves oblanceolate, ± clasping; bracts among heads generally < clusters; involucre 3.5–4 mm; phyllaries in 4–5 series ..... [G. stachydifolia]

5' Mid and distal cauline leaves linear to 

lanceolate 

Narrowly elongate, widest in the basal half, often tapered to an acute tip.

, oblanceolate, or spoon-shaped, not ± clasping; bracts among heads < or > than clusters; involucre 2.5–3.5 mm; phyllaries in 3–4(5) or 5–7 series

6. Involucre 3–3.5 mm, not purple, base generally ± glabrous to occasionally sparsely cobwebby; phyllaries in 5–7 series, outer ovate-triangular, 1/3–1/2 × inner, acute-acuminate; flower Jun–Jul ..... G. calviceps

6' Involucre 2.5–3 mm, generally ± purple proximally, base cobwebby; phyllaries in 3–4(5) series, outer ovate-triangular, 1/2–2/3 × inner, acute; flower Mar–Apr ..... G. stagnalis

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