Arrowhead |
Inflorescence, male flower, leaf and infructescence of the arrowhead
| Sagittaria sagittifolia L.: | |
| Blooming period: | June–August |
| Height: | 20–100 cm |
| Flowers: | bisexual, actinomorphic, Ø approx. 2 cm, stamens many, carpels many |
| Petals: | 3, white with red-violet spot at base |
| Sepals: | 3 |
| Stem leaves: | clustered basal, floating leaves ovoid or hastate, air leaves arrow-shaped, submersed leaves linear |
Plant perennial, rarely annual, growing in water, with milky sap, herbaceous, with up to 18 cm long surface runners, with a bulbous, 1-1.5 cm thick rhizome (rootstock).
Stem erect, glabrous, triangular.
Air leaves long-petiolate, simple, entire, shiny, wide or narrow arrow-shaped, lobes of the basal blade usually shorter or as long as the rest of the blade.
Floating leaves long stalked, simple, entire, ovoid, hastate or arrow-shaped.
Submersed leaves sessile, strap-shaped.
Flowers in racemose inflorescences of 2–10 consecutive trimerous false whorls. Inflorescences rarely branched at the base.
The flower stalks are each surrounded by a triangular bract. The upper flowers are male and stalked twice as long as the lower female flowers. Rarely, the lower flowers are hermaphrodite.
The 3 petals are round, white and have red-violet claws. The 3 sepals are about half the size and are arranged offset in relation to the petals.
Male flowers have many stamens that are usually arranged in 8 rows. They have red-violet anthers and sometimes some vestigial ovarys.
Female flowers have numerous, not fused carpels, capitate arranged, and sometimes some sterile stamens. Rarely are formed exclusively male flowers.
After pollination, mainly mediated by flies, the carpels form a spherical head, up to 2 cm broad. The aggregated fruit consist of closely spaced, strongly flattened, single-seeded, obovoid, 4–6 mm long nutlets (achenes), with a short, hooked beak.
| Floral formula: |
| * K3 C3 A∞ bzw. * K3 C3 G∞ superior |
Occurrence:
In swamps, ponds and slow-flowing waters. Prefers warm, very moist,
slightly alkaline and nutritious locations.
Distribution:
Temperate
Europe and Asia.