Black Knapweed

Latin Name: Centaurea Nigra

Flowering stem by Steve C.

Flowering stem by Steve C.

Family: Asteraceae.

Known Hazards: None known.

Habitat: Grassland, waysides, cliffs etc to 600 metres.

Edibility Rating: 1 (1-5)

Medicinal Rating: 2 (1-5)

Physical Characteristics: Perennial erect herb to 0.9 (rarely to 1.2) m high. Stems ribbed, cobwebby, sometimes hairless with age. Basal leaves entire to lobed, 6–30 cm long, 0.5–3.5 cm wide, narrowed at base, withering in mature plants; lower stem leaves entire to toothed 1–8 cm long, 0.2–1 cm wide; upper leaves smaller, entire to sparsely toothed, oblong to lanceolate. Seeds flattened, 3–4 mm long, sparsely short hairy, pale brown, topped by a few bristles to 1 mm long or without bristles.
Flowers: Many small flowers (florets) in solitary heads at ends of branches. Flowers spring to autumn.The flowers are hermaphrodite (has both male and female organs) and are pollinated by Bees, flies, Lepidoptera (Moths & Butterflies). The plant is self-fertile.


Distinguishing features: Distinguished by presence of rhizomes; erect habit; leaves not spiny; flowerheads mostly 12–18 mm wide; middle bracts with a narrow waist between base and fringed upper section, fringe hairy, dark brown top blackish; all florets tubular, pink to purple (rarely white), arising from a hairy receptacle, outer petal-like florets with forked tips.

Dispersal: Spread by seed, rhizomes and root pieces.

Edible Uses

Flower petals – raw. Added to salads.


Medicinal Uses

Diaphoretic; Diuretic; Tonic. The roots and seeds are diaphoretic, diuretic, tonic and vulnerary. The plant once had a very high reputation as a healer of wounds.

Other Uses

None known

Notes: Seeds germinate in cooler months, plants maturing in summer and dying back in autumn. Probably introduced as an ornamental in early 1900s.Mainly invades overgrazed and poor pastures. Plants not eaten by stock. Reduces carrying capacity of pasture. There is some overseas evidence that Black Knapweed reduces growth of nearby plants.

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