Centaurea nigra
Encyclopedia
Centaurea nigra is a species of flowering plant in the daisy family
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...
known by the common names Lesser Knapweed, Common Knapweed and Black Knapweed. A local vernacular name is Hardheads.
It is native to Europe but it is known on other continents as an introduced species
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
and often a noxious weed.
Description
It is a perennial herb growing up to about a metre in height.The leaves are up to 25 centimetres long, usually deeply lobed, and hairy. The lower leaves are stalked, whilst the upper ones are stalkless.
The inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
contains a few flower heads
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....
, each a hemisphere of black or brown bristly phyllaries
Bract
In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...
. The head bears many small bright purple flowers. The fruit is a tan, hairy achene
Achene
An achene is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate and indehiscent...
2 or 3 millimetres long, sometimes with a tiny, dark pappus
Pappus (flower structure)
The pappus is the modified calyx, the part of an individual disk, ray or ligule floret surrounding the base of the corolla, in flower heads of the plant family Asteraceae. The pappus may be composed of bristles , awns, scales, or may be absent. In some species, the pappus is too small to see...
. Flowers July until September.
flowers sometimes are yellow, or white
Wildlife value
Important for Gatekeeper butterfly, GoldfinchGoldfinch
Goldfinch may refer to any of the following species of bird from the genus Carduelis:* American Goldfinch, Carduelis tristis* European Goldfinch, Carduelis carduelis* Lawrence's Goldfinch, Carduelis lawrencei...
, Honey bee
Honey bee
Honey bees are a subset of bees in the genus Apis, primarily distinguished by the production and storage of honey and the construction of perennial, colonial nests out of wax. Honey bees are the only extant members of the tribe Apini, all in the genus Apis...
, Large skipper
Large Skipper
The Large Skipper is a butterfly of the Hesperiidae family, which occurs throughout Europe. It was long known as Ochlodes venata, but this is a Far Eastern relative. There is still some dispute whether this species should be considered a distinct species or included in O...
, Lime-speck pug moth, Meadow Brown
Meadow Brown
The Meadow Brown, Maniola jurtina, is a butterfly found in European meadows, where its larvae feed on grasses, such as Sheep's Fescue.Similar species are Gatekeeper and Small Heath ....
, Painted lady, Peacock, Red admiral, Small copper, Small skipper
Similar species
Brown Knapweed Centaurea jaceaCentaurea jacea
Centaurea jacea is a species of herbaceous perennial plants in the genus Centaurea native to dry meadows and open woodland throughout Europe...
is different in having pale brown bract appendages, no pappus
Pappus (flower structure)
The pappus is the modified calyx, the part of an individual disk, ray or ligule floret surrounding the base of the corolla, in flower heads of the plant family Asteraceae. The pappus may be composed of bristles , awns, scales, or may be absent. In some species, the pappus is too small to see...
. Flowers August until September.