Nodding beggarticks |
Flowers and stem of the nodding beggarticks
| Bidens cernuus L.: | |
| Blooming period: | August–September |
| Height: | 10–100 cm |
| Flowers: | in heads, Ø of the heads 15–25 mm, stamens: 5, styles: 1 |
| Ray florets: | yellow, sometimes missing |
| Disc florets: | yellow |
| Calyx: | transformed into 3–4 awns |
| Stem leaves: | opposite, simple, half-stem-embracing |
| Basal leaves: | missing |
Plant annual, herbaceous.
Stem erect, pale green, rough, sparsely branched. When prostrate, may rooting at the lower nodes.
Stem leaves opposite, stalkless, half-stem-embracing, oval to lanceolate, acute to acuminate, glabrous. Leaf margins entire, coarsely toothed or serrated, sometimes ciliated.
Flower heads about 50 mm long, peduncles leafless, nodding at the fruiting time. The receptacle is flat, later hemispherical.
The involucre consists of 2 rows. The outer phyllaries are large and often leaf-like, spread or bent back at fruiting time. The inner ones are small, yellowish, greenish or brownish, membranous or with membranous margins and with black stripes.
The 6–8 marginal ray florets are sterile, yellow and arranged in a single row. Ligules 2–15 mm long, at the apex sometimes 3-dentate, sometimes they are missing.
The inner 40–100 disc florets are hermaphrodite, 3-4 mm long, 5-dentate and yellow. At the base they have a lanceolate, 6 mm long, dull, yellow, chaffy leaf with 3 brown stripes and often with an apiculate tip.
After insect or self-pollination an approximately 6 mm long nut fruit (achene) is formed. It can be flattened or 4-angular, black to brown, covered with downwards directed bristles and with usually 3-4 awns. Plants very diversiform!
| Floral formula: |
| ↓ K=awns C(5) A0 G0 and * K=awns [C(5) A5(connate)] G(2) inferior |
Occurrence:
On
banks of rivers, ditches and ponds. Prefers warm, slightly alkaline,
wet and very nitrogenous locations.
Distribution:
Europe,
North America, Asia.