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• Dichotomous Key
• Asteraceae
• Asteraceae Group 2
• Centaurea
• Centaurea scabiosa

Centaurea scabiosa — greater knapweed

Facts

Greater knapweed is native to Europe and occasionally escapes from cultivation in some parts of North America. Its large flowers make it a popular garden ornamental, and it is also used in traditional medicine to treat kidney problems, mouth ulcers, and to aid the healing of wounds.

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 outer side hair type

  • the bracts are hairy, with simple hairs on their outer surface
  • 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 lanceolate (widest above the base, then taper narrowly towards the tip)
  • 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

  Bract tip shape

  NA

  Bract width

  3–4

  Bracts

  there are at least two distinct forms of bracts in different cycles

  Disk flower color

  • blue to purple
  • pink to red
  • white

  Disk flower lobe number

  5

  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

  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, but are bigger than the flowers 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 head width

  50–60 mm

  Flower type in flower heads

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

  Height of flower head base

  15–25 mm

  Inflorescence branching (Solidago)

  NA

  Inflorescence shape

  the inflorescence is flat-topped in profile

  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
  • the ovary is compressed (flattened)

  Ovary hair type

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

  Ovary hairs

  the ovary has hairs on it

  Ovary profile

  • in profile, the ovary is oblong (roughly rectangular but rounded at the ends)
  • in profile, the ovary is roughly elliptical (widest in the middle, tapering to both ends)

  Ray flower color

  • blue to purple
  • pink to red
  • white

  Ray flower reproductive parts

  NA

  Ray flowers

  0

  Ray length

  0 mm

  Reproductive system

  all the flowers on the plant contain both carpels and stamens

  Scale tip

  NA

  Smaller bracts at base of bracts

  there is no smaller, outer cycle of bracts

  Style branch number

  the style has two branches

  Width of flower head base

  18–25 mm

• Fruits or seeds

  Ovary length in developed fruit

  4–5.5 mm

  Seed hair tuft color

  the pappus hairs are white or off-white

  Seed hair tuft length

  3–6 mm

  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

  Leaf blade glands

  the leaf blades have glandular (translucent) dots or scales

  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 perennial, it shows evidence of previous year's leaves, stems or stem bases

  Spines on plant

  the plant has no spines

  Underground organs

  there is a thickened taproot on the plant

• Leaves

  Hairs on underside of leaf blade

  the underside of the leaf is fuzzy or hairy

  Hairs on upper side of leaf blade

  • the upper side of the leaf is fuzzy or hairy
  • the upper side of the leaf is not hairy, or has very few hairs

  Leaf arrangement

  • alternate: there is one leaf per node along the stem
  • the leaves are growing only at the base of the plant (basal)

  Leaf blade base

  the leaf has a distinct 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
  • the edge of the leaf blade has teeth

  Leaf blade hairs

  • the leaf blade has hairs with glands at their tips
  • the leaf blade has simple hairs with no glands, and not tangled or wooly

  Leaf blade length

  100–250 mm

  Leaf blade shape

  • the leaf blade is lanceolate (lance-shaped; widest below the middle and tapering at both ends)
  • the leaf blade is oblong (rectangular but with rounded ends)
  • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)

  Leaf blade tip

  • the tip of the leaf blade is acute (sharply pointed)
  • the tip of the leaf blade is obtuse (bluntly pointed)

  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 leaf stalks

  Leaf tip extension

  NA

  Leaf type

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

  Specific leaf type

  • the leaf has a row of two or more lobes on each side of the central axis
  • the leaf has a row of two or more lobes on each side of the central axis, and each lobe itself has rows of lobes on each side of the lobe's central axis

• Place

  Habitat

  terrestrial

  New England state

  • Connecticut
  • Maine
  • New Hampshire

  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 internode hair direction

  the hairs point mostly upwards to outwards

  Stem internode hair type

  • the hairs on the stem are plain, without glands or branches, and not tangled
  • the stem has no hairs between the nodes

  Stem internode hairs

  • the stem has hairs between the nodes
  • the stem has no hairs between the nodes

Wetland status

Not classified

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae