Centaurea cyanus L.

garden knapweed

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New England Distribution

Adapted from BONAP data

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North America Distribution

Adapted from BONAP data

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Facts About

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

Habitat
terrestrial
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf type
leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
Leaf arrangement
alternate: there is one leaf per node along the stem
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
Flower type in flower heads
the flower head has disk flowers only, and lacks the strap-shaped flowers
Ray flower color
NA
Tuft or plume on fruit
at least a part of the plume is made up of fine bristles
Spines on plant
the plant has no spines
Leaf blade length
30–100 mm
Disk flower number
21-50
Show All 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 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 (i.e., lobed or unlobed but not separated into leaflets)
    Leaflet number
    0
    Specific leaf type
    the leaves are simple (i.e., 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

Distribution

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

Conservation Status

Exact status definitions can vary from state to state. For details, please check with your state.

Massachusetts
not applicable (S-rank: SNA)

Native to North America?

No

Synonyms

  • Centaurea pulchra DC.
  • Centaurea segetum Hill
  • Leucacantha cyanus (L.) Nieuwl. & Lunell

Family

Asteraceae

Genus

Centaurea

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Information from Dichotomous Key of Flora Novae Angliae

3.  Centaurea cyanus L. E

garden knapweed. Centaurea segetum Hill; C. pulchra DC.; Leucacantha cyanus (L.) Nieuwl. & Lunell • CT, MA, ME, NH, RI, VT. Roadsides, fields, waste areas, rubbish heaps. Centaurea cyanus often shows involucral bracts that change colors from base to apex of the involucre. The visible portion of the basal ones are frequently white to pale, the middle ones green (in life) 
to brown (in drying), and the apical ones tinged with or wholly pink.