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• Centaurea cyanus

Centaurea cyanus — garden knapweed

Facts

Garden knapweed is a commonly cultivated ornamental originating in southern Europe. It is sometimes included in wildflower seed mixes and it often escapes from cultivation. Cultivars include a range of flower colors from white and pink, to blue-purple.

Habitat

Anthropogenic (man-made or disturbed habitats), meadows and fields

Characteristics

• Flowers

  Bases of bract appendages

  bases of bract appendages are u-shaped, with a tiny projecting edge running across from one appendage to the next

  Bract color

  the bracts are not colored or tinged with with pink, red or purple

  Bract cycle number

  there are three or more cycles of bracts

  Bract margins

  • there are few or no fine hairs along the bract margins
  • there are fine hairs along the bract margins

  Bract outer side hair type

  • the bracts are hairy on their outer surfaces, with curled, tangled, matted, or woolly hairs
  • the bracts are not hairy on their outer surface

  Bract outer side hairs

  • the bracts are hairy on their outer surfaces
  • the bracts are not hairy on their outer surfaces

  Bract shape

  • the main bracts are oblong (roughly rectangular but rounded at the ends)
  • the main bracts are ovate (egg-shaped)

  Bract spines

  the bracts have no spines

  Bract tip color

  the tips are a different color from the center of the bract

  Bract tip extension appearance

  the projections from the bract tips have further projections from their edges, like a fringe

  Bract tip extension edge

  there are projections from the bract tips

  Bract tip orientation

  the bracts are pressed against the plant, or spreading out at the tips

  Bracts

  • the bracts in separate cycles are similar or gradually changing from the outer to inner cycles
  • there are at least two distinct forms of bracts in different cycles

  Disk flower color

  • blue to purple
  • white

  Disk flower lobe number

  5

  Disk flower number

  21-50

  Disk flower reproductive parts

  the disk flower has both pollen- and seed-producing parts

  Disk flower shape

  • the disk flower is tube-shaped (cylindrical), or gradually widening like a funnel
  • the disk flower looks different from the choices given

  Flower head number

  each flowering stem has only one to three flower heads on it

  Flower head outer flowers

  at the outer edge of the flower head, the flowers have no enlarged lobe or strap, and are of similar size as those in the center of the disk

  Flower head platform

  the base has fine, short hairs on it

  Flower head platform surface

  NA

  Flower head position

  each of the flower heads is separate on its own peduncle (stalk), not clustered in groups

  Flower head profile

  the disk is flat or nearly flat across the top

  Flower head shape

  the sides of the flower head are roughly parallel, like a cylinder

  Flower type in flower heads

  the flower head has disk flowers only, and lacks the strap-shaped flowers

  Height of flower head base

  12–16 mm

  Inflorescence branching (Solidago)

  NA

  Inflorescence shape

  • NA
  • the inflorescence is flat-topped in profile

  Inflorescence stem

  hairs are present on the stem of the inflorescence

  Ovary attachment

  the ovary is attached at the side near the base, rather than at the base

  Ovary beak

  there is no beak on the ovary

  Ovary cross-section

  the ovary has five or more corners in cross-section

  Ovary hair type

  the ovary has hairs on it, but the hairs have no glands

  Ovary hairs

  the ovary has hairs on it

  Ovary lines or ribs

  there are no lines or ribs visible on the ovary

  Ovary profile

  in profile, the ovary is roughly egg-shaped, but widest above the middle

  Ray flower color

  NA

  Ray flower reproductive parts

  NA

  Ray flowers

  0

  Reproductive system

  all the flowers on the plant contain both carpels and stamens

  Scale tip

  NA

  Style branch number

  the style has two branches

  Width of flower head base

  10–17 mm

• Fruits or seeds

  Ovary length in developed fruit

  4–5 mm

  Ovary width in developed fruit

  1.5–2 mm

  Seed hair tuft color

  the pappus hairs are pale red to red-brown or purple

  Seed hair tuft length

  2–4 mm

  Seed tuft scale number

  0

  Seed tuft type

  the pappus is made of very fine hairs or bristles

  Top of disk flower ovary

  NA

  Tuft or plume on fruit

  at least a part of the plume is made up of fine bristles

• Glands or sap

  Sap

  the sap is clear and watery

• Growth form

  Growth form

  the plant has one or more free-standing stems

  Plant lifespan

  the plant is annual, it lacks evidence of previous years' growth

  Spines on plant

  the plant has no spines

• Leaves

  Hairs on underside of leaf blade

  the underside of the leaf is fuzzy or hairy

  Leaf arrangement

  alternate: there is one leaf per node along the stem

  Leaf blade base

  the leaf has no petiole

  Leaf blade base shape

  the base of the leaf blade is cuneate (wedge-shaped, tapers to the base with relatively straight, converging edges), or narrow

  Leaf blade edges

  • the edge of the leaf blade has lobes, or it has both teeth and lobes
  • the edge of the leaf blade has no teeth or lobes

  Leaf blade hairs

  the leaf blade has tangled or woolly-looking hairs

  Leaf blade length

  30–100 mm

  Leaf blade shape

  • the leaf blade is lanceolate (lance-shaped; widest below the middle and tapering at both ends)
  • the leaf blade is linear (very narrow with more or less parallel sides)

  Leaf blade tip

  the tip of the leaf blade is acute (sharply pointed)

  Leaf blade width

  Up to 10 mm

  Leaf disposition

  the leaves are nearly similar in size, prominence of teeth, and length of stalks throughout the stem

  Leaf spines

  there are no spines on the leaf edges

  Leaf stalk

  the leaves have no leaf stalks, but attach directly to the stem

  Leaf stalk length

  0 mm

  Leaf tip extension

  NA

  Leaf type

  leaves are simple (lobed or unlobed but not separated into leaflets)

  Leaflet number

  0

  Specific leaf type

  the leaves are simple (lobed or unlobed but not separated into leaflets

• Place

  Habitat

  terrestrial

  New England state

  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont

  Specific habitat

  • man-made or disturbed habitats
  • meadows or fields

• Stem, shoot, branch

  Leaves on stem

  there is at least one full leaf above the base of the flowering stem

  Stem bloom

  NA

  Stem internode hair direction

  the hairs point mostly upwards to outwards

  Stem internode hair type

  at least some of the hairs on the stem are tangled, matted or woolly

  Stem internode hairs

  the stem has hairs between the nodes

Wetland status

Occurs only in non-wetlands. (Wetland indicator code: UPL)

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae