Greater knapweed |
Flower head, involucre and stem leaf of the greater knapweed
| Centaurea scabiosa L.: | |
| Blooming period: | June–September |
| Height: | 30–120 cm |
| Flowers: | in heads, Ø of the heads 30–50 mm, stamens: 5, styles: 1 |
| Ray florets: | missing |
| Disc florets: | red violet to purple |
| Calyx: | transformed into pappus |
| Stem leaves: | alternate, pinnatipartite |
| Basal leaves: | stalked, pinnatipartite, missing at the flowering season |
Plant perennial, herbaceous, with a thick, woody taproot.
Stem erect, simple or slightly branched, strong, grooved, slightly hairy to glabrous.
Stem leaves alternate, shortly coarse-haired. Lower leaves stalked, 1 to 2-fold pinnatipartite, leaf segments oblong to linear, pointed. Leaves decreasing upwards in size, sessile, entire or pinnatipartite.
Flower heads usually solitary on 2.5 to 13 cm long, more or less glabrous stalks that are slightly thickened below the flower head and equipped with a bract. Receptacle flat and bristly.
Phyllaries in 6 or 7 rows, tightly imbricated, dark green with a fringed, blackish margin. The outer phyllaries are ovate and pointed. The inner ones are elongated and rounded. Involucre ovate to hemispherical, later bell-shaped.
The flower head consists exclusively of red-violet, rarely white tubular flowers, at the base without chaffy leaves. Outer florets usually significantly extended (35–40 mm long), sterile, zygomorphic, funnel-shaped, 5-toothed. Inner ones almost radiate, hermaphrodite, 5-toothed, 20-25 mm long.
After pollination by bees, bumblebees or butterflies, the inferior ovary forms an up to 5 mm long nut fruit (achene) which is puberulent, elongated, flattened and with many irregular, up to 5 mm long white bristles at the apex (pappus).
In addition to the subspecies Centaurea scabiosa L. ssp. scabiosa, wherein the involucre appears spotted black-green, there is the ssp. alpestris with a completely black involucre.
Centaurea scabiosa may form bastards with C. stoebe.
| Floral formula: |
| *–↓ K=pappus [C(5) A5(connate)] G(2) inferior |
Occurrence:
Dry
meadows and roadsides, waste places, railway land. Prefers dry and
calcareous soils.
Distribution:
Europe,
introduced in North America.