Black Knapweed, Lesser knapweed
Centaurea nigra
Family: Asteraceae or Compositae
What it is like
Centaurea nigra is a PERENNIAL growing to 0.6 m (2ft). See above for USDA hardiness. It is hardy to UK zone 5 and is not frost tender. It is in flower from June to September, and the seeds ripen from August to October. The species is hermaphrodite (has both male and female organs) and is pollinated by Bees, flies, Lepidoptera (Moths & Butterflies). The plant is self-fertile. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils and can grow in very alkaline soils. It cannot grow in the shade. It prefers dry or moist soil and can tolerate drought.
Height (m): 0.6
Where it is found
Grassland, waysides, cliffs etc to 600 metres.
Western Europe, including Britain, from Spain to Norway, east to Germany and Switzerland.
Conservation Status: This taxon has not yet been assessed.
Countries/locations it is found in
America, Australia, Britain, Europe, North America, Tasmania.
How it is used
Food
Rating: 1
Flower petals - raw. Added to salads.
Medicine
Rating: 2
The roots and seeds are diaphoretic, diuretic, tonic and vulnerary. The plant once had a very high reputation as a healer of wounds.
Diaphoretic: Induces perspiration.
Diuretic: Acts on the kidneys, promoting the flow of urine.
Tonic: Improves general health. Slower acting than a stimulant, it brings steady improvement.
Other
Rating: 0
How it is grown
Succeeds in ordinary garden soil. Prefers a well-drained fertile soil and a sunny position. Tolerates dry, low fertility and alkaline soils. Established plants are tolerant of considerable neglect, thriving and even self-sowing in dense weed growth. Members of this genus are rarely if ever troubled by browsing deer.
Propagating it: Seed - sow April in a cold frame. When they are large enough to handle, prick the seedlings out into individual pots and plant them out into their permanent positions in the summer. Division in autumn. Very easy, larger clumps can be replanted direct into their permanent positions, though it is best to pot up smaller clumps and grow them on in a cold frame until they are rooting well. Plant them out in the summer or following spring. This should be done at least once every three years in order to maintain the vigour of the plant. Basal cuttings in spring. Harvest the shoots when they are about 10 - 15cm long with plenty of underground stem. Pot them up into individual pots and keep them in light shade in a cold frame or greenhouse until they are rooting well. Plant them out in the summer.
Best place to grow: Meadow; Cultivated Beds;
Habit: Perennial
Hardiness: 4-8
Growth:
Soil: Light (sandy), medium, heavy (clay)
Shade: No shade
Moisture: Dry, moist
Things to keep in mind
This plant can be weedy or invasive. Native to Europe; as an introduced species in other areas it can be a noxious weed. Washington, US - Class B noxious weed, Noxious weed seed and plant quarantine.
Its other names
Local names
Hardhead, lesser knapweed, common knapweed, black knapweed.