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Carduus acanthoides — spiny plumeless-thistle

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Facts

This non-native species is considered a noxious weed and prohibited in many states across the country. It is a very spiny species, and spreads rapidly by producing many thousands of seeds per plant.

Habitat

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

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
terrestrial
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • 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
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
there are spines on the plant
Leaf blade length
100–300 mm
Flower head width
18–25 mm
Show all characteristics
  • Flowers

    Bases of bract appendages
    NA
    Bract cycle number
    there are three or more cycles of bracts
    Bract margins
    there are fine hairs along the bract margins
    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 shape
    • the main bracts are lanceolate (widest above the base, then taper narrowly towards the tip)
    • the main bracts are linear (long and very narrow)
    Bract spines
    there is just one simple spine at the tip of the bract
    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
    the tips of the bracts acute (have a sharp point)
    Bract width
    1–2
    Disk flower color
    • blue to purple
    • 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 abruptly widened at some point below the lobes
    • the disk flower is tube-shaped (cylindrical), or gradually widening like a funnel
    Disk width
    15–25 mm
    Flower head number
    • each flowering stem has four or more flower heads on it
    • 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
    • some or all the flower heads are grouped in clusters of two or more
    Flower head profile
    • the disk is conical across the top
    • the disk is flat or nearly flat across the top
    • the disk is rounded across the top
    Flower head shape
    the flower head is hemispherical (like the bottom half of a sphere)
    Flower head width
    18–25 mm
    Flower type in flower heads
    the flower head has disk flowers only, and lacks the strap-shaped flowers
    Height of flower head base
    14–20 mm
    Inflorescence branching (Solidago)
    NA
    Inflorescence shape
    the inflorescence is flat-topped in profile
    Ovary attachment
    • the ovary is attached at or near the base
    • the ovary is attached at the side near the base, rather than at the base
    Ovary cross-section
    the ovary is compressed (flattened)
    Ovary hair type
    the ovary has no hairs on it
    Ovary hairs
    the ovary has no hairs on it
    Ovary profile
    • in profile, the ovary is oblong (roughly rectangular but rounded at the ends)
    • in profile, the ovary is roughly egg-shaped
    • in profile, the ovary is roughly egg-shaped, but widest above the middle
    Ovary surface
    the ovary surface has no points, bumps or wrinkles, though it may have lines, ribs or wings
    Peduncle length
    Up to 100 mm
    Ray flower color
    NA
    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
    Width of flower head base
    10–25 mm
  • Fruits or seeds

    Number of pappus parts
    11 or more
    Ovary length in developed fruit
    2.5–3 mm
    Seed hair tuft bases
    the pappus hairs are attached to one another near the base
    Seed hair tuft color
    the pappus hairs are white or off-white
    Seed hair tuft details
    the pappus hairs are hooked or barbed
    Seed hair tuft length
    11–13 mm
    Seed hairs uniform
    all the pappus hairs are approximately the same length
    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

    Leaf blade glands
    the leaf blades have no 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 annual, it lacks evidence of previous years' growth
    • the plant is biennial, it appears as either first year (non-reproductive) plants or second year plants with flowers or fruit
    Spines on plant
    there are spines on the plant
    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
    Leaf blade base
    • the leaf has a distinct petiole
    • the leaf has no petiole
    Leaf blade bloom
    the underside of the leaf has no noticeable bloom
    Leaf blade edges
    the edge of the leaf blade has lobes, or it has both teeth and lobes
    Leaf blade hairs
    • the leaf blade has simple hairs with no glands, and not tangled or wooly
    • the leaf blade has tangled or woolly-looking hairs
    Leaf blade length
    100–300 mm
    Leaf blade shape
    • the leaf blade is elliptic (widest near the middle and tapering at both ends)
    • the leaf blade is oblanceolate (lance-shaped, but with the widest point above the middle of the leaf blade)
    Leaf blade surface colors
    there is no noticeable color variation on the upper surface of the leaf
    Leaf blade veins
    the leaf blade has one main vein running from the base towards the tip
    Leaf blade width
    20–80 mm
    Leaf disposition
    • the leaves are nearly similar in size, prominence of teeth, and length of stalks throughout the stem
    • the lower leaves are larger, toothier, and/or on longer stalks than the upper leaves
    Leaf spines
    there are spines along the leaf edges
    Leaf stalk
    • the leaves have leaf stalks
    • the leaves have no leaf stalks, but attach directly to the stem
    Leaf stalk length
    At least 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 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
    • Massachusetts
    • Rhode Island
    • Vermont
    Specific habitat
    • man-made or disturbed habitats
    • meadows or fields
  • Scent

    Plant odor
    the plant does not have much of an odor
  • Stem, shoot, branch

    Flowering stem cross-section
    the flowering stem is circular, or with lots of small angles
    Leaves on stem
    there is at least one full leaf above the base of the flowering stem
    Stem bloom
    there is no powdery or waxy film on the 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
    Stem internode hairs
    • the stem has hairs between the nodes
    • the stem has no hairs between the nodes
    Stem wings
    the stem has wings on it that run down the stem from the leaf nodes

Wetland status

Not classified

In New England

Distribution

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

Conservation status

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

ssp. acanthoides

Massachusetts
not applicable (S-rank: SNA)

Subspecies and varieties

Our subspecies is Carduus acanthoides L. ssp. acanthoides.

From Flora Novae Angliae dichotomous key

1.  Carduus acanthoides L. ssp. acanthoides E

spiny plumeless-thistle. CT, MA, ME, RI, VT. Roadsides, fields, pastures.

Native to North America?

No

Sometimes confused with

Carduus crispus:
undersurface of leaves with two types of hairs: longer, curling, septate hairs on the veins and sparse, woolly hairs inbetween (vs. C. anthoides, with the undersurface of leaves with only type of hair: curling and septate).

Family

Asteraceae

Genus

Carduus