Cornflower |
Flower head, involucre, infructescence, stem and leaf of the cornflower
| Cyanus segetum Hill: | |
| Blooming period: | June–Oktober |
| Height: | 20–100 cm |
| Flowers: | in heads, Ø of the heads 21–30 mm, stamens: 5, styles: 1 |
| Ray florets: | missing |
| Disc florets: | mostly blue |
| Calyx: | transformed into bristles |
| Stem leaves: | alternate, linear to lanceolate |
| Basal leaves: | lanceolate, lyrate or pinnatifid, missing at the flowering season |
Plant
annual, rarely biennial, herbaceous, with a long, spindle-shaped
taproot.
Stem
erect, usually slightly branched
in the upper part, angular, loosely covered with woolly hairs.
Stem leaves alternate, acute, not decurrent, underneath sometimes grey tomentose or woolly, upper surface loosely cobwebby. Lower leaves lanceolate or lyrate to pinnatifid, shortly stalked. Leaves in the upper part linear, sessile. Leaves entire.
Flower heads
solitary or in racemose or corymbose inflorescences with long, slender
petioles that are barely thickened below the flower heads and
bracteate. Receptacle flat with
long, flat bristles.
The
phyllaries are arranged
imbricated in 4–6 rows. The outer and middle
bracts are egg-shaped, appressed and green. The inner ones are
lanceolate and often slightly violet at the apex. Phyllaries with
narrowly
membranous margins, often loosely cobwebby, frayed serrated at the
apex. Lobes white to dark brown, membranous. Involucre
11–16 mm in
diam., urn-shaped.
The flower head consists entirely of blue or rarely white tubular flowers, at the base without chaffy leaves. Outer florets (15) greatly elongated, sterile, zygomorphous, funnel-shaped, 20–25 mm long, with about 8 lobes. Inner florets (12–20) nearly actinomorphic, hermaphrodite, with 5 lobes, 10–15 mm long.
After pollination by bees, bumblebees or butterflies, the inferior ovary forms a 4–5 mm long nut fruit (achene) which is finely hairy and barrel-shaped. At the apex it shows about 50, 2–3 mm long, fine, unequal bristles.
| Floral formula: |
| *–↓ K=bristles [C(5)
A5(connate)] G(2) inferior |
Occurrence:
At
fringes of crop fields and in ruderal areas. Prefers slightly warm and
sandy locations.
Distribution:
Originally
the Mediterranean, today widespread throughout the world by seeds and
by the use as a ornamental plant.