Key to Centaurea

View taxon page for Centaurea

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

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

1. Corolla yellow

2. Heads 

sessile 

Without a petiole, peduncle, pedicel, or other kind of stalk.

or subsessile, subtended by leaf-like bracts ..... C. benedicta

2' Heads generally peduncled (if not, then subtending bracts reduced)

3. Corolla 25–30 mm ..... C. sulphurea

3' Corolla generally 10–20 mm

4. Central spine of main phyllaries 5–10 mm, ± purple ..... C. melitensis

4' Central spine of main phyllaries 10–25 mm, straw-colored ..... C. solstitialis

1' Corolla white to pink, blue, or purple

5. Main phyllaries ± spine-tipped

6. Main phyllary tip-spine 6–25 mm

7. Pappus 0 ..... C. calcitrapa

7' Pappus present, 0.3–2.5 mm

8. Involucre body 8–14 mm diam, widely ovoid ..... C. iberica

8' Involucre body 5–10 mm diam, narrowly ovoid ..... C. pouzinii

6' Main phyllary tip-spine 1–5 mm

9. Outer flower corollas expanded, ± ray-like, >> disk flower corollas, 25–35 mm, pink-purple ..... C. diluta (2)

9' Outer flower corollas not or barely expanded, = or slightly > disk flower corollas, 7–13 mm, white to pink or pale purple

10. Involucre 10–13 mm; disk flower corolla 12–13 mm ..... C. diffusa

10' Involucre 7–8 mm; disk flower corolla 7–9 mm ..... C. virgata subsp. squarrosa

5' Main phyllaries not spine-tipped

11. Annual

12. Herbage ± 

tomentose 

Covered with densely interwoven, generally matted hairs.

; disk flower corolla 10–15 mm ..... C. cyanus

12' Herbage 

puberulent 

Minutely hairy.

or ± glabrous, sometimes thinly cobwebby; disk flower corolla ± 20 mm ..... C. diluta (2)

11' Biennial or 

perennial 

Completing life cycle (germination through death) in more than two years or growing seasons, generally non-woody (at least above ground) to woody; includes perennial herbs as well as subshrubs to trees; the abbreviation 'per' only refers to perennial herb, not to the word 'perennial' alone.

 herb

13. Outer and inner flowers 

bisexual 

Both male and female reproductive parts occurring and functional in the same plant or structure (e.g., flower, spikelet, inflorescence).

; corollas all ± equal ..... C. jacea subsp. nigra

13' Outer flowers sterile, inner flowers bisexual; sterile flower corollas > bisexual flower corollas

14. Herbage densely gray-tomentose ..... C. cineraria

14' Herbage ± green, sometimes thinly cobwebby

15. Involucre 10–13 mm ..... C. stoebe subsp. australis

15' Involucre 15–18 mm

16. Phyllary appendages scarious, light brown, concave, 

entire 

Having margins that are continuous and smooth (i.e., without teeth, lobes, etc.).

to coarsely 

dentate 

Having margins with sharp, relatively coarse teeth pointing outward, not tipward.

..... C. jacea subsp. jacea

16' Phyllary appendages light to dark brown, flat to ± concave, coarsely dentate to dissected into fine, wire-like 

lobes 

1. A major expansion or bulge, such as on the margin of a leaf, sepal, or petal, or on the surface of an ovary. 2. The free tips of otherwise fused structures, such as sepals or petals; larger than teeth.

..... C. jacea nothosubsp. pratensis

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