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Onopordum acanthium — Scotch cotton-thistle

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Facts

Scotch cotton-thistle is a biennial, native to Europe and western Asia, and invasive in many other parts of the world. It is a serious weed of western rangelands, forming dense, impenetrable stands and reducing forage quality for livestock. Scotch thistle has been the national emblem of Scotland since the thirteenth century.

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
  • 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
  • basal: the leaves are growing only at the base of the plant
Leaf blade edges
the edge of the leaf blade has teeth
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
100–600 mm
Flower head width
20–50 mm
Disk flower number
more than 50
Show all characteristics

  • Flowers

    Bract cycle number
    there are three or more cycles of bracts
    Bract outer side hairs
    the bracts are hairy on their outer surfaces
    Bract shape
    • the main bracts are linear (long and very narrow)
    • the main bracts are ovate (egg-shaped)
    Bract spines
    there is just one simple spine at the tip of the bract
    Bract tip color
    the tips are a different color from the center of the bract
    Bract tip orientation
    the tips of the bracts curve outwards and downwards from the plant
    Bract width
    2–2.5
    Bracts
    the bracts in separate cycles are similar or gradually changing from the outer to inner cycles
    Disk flower color
    • blue to purple
    • white
    Disk flower number
    more than 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
    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 no bristles or papery scales
    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 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
    20–50 mm
    Flower type in flower heads
    the flower head has disk flowers only, and lacks the strap-shaped flowers
    Height of flower head base
    20 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 or near 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 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)
    Ovary surface
    the ovary surface is textured with tiny points, bumps or wrinkles
    Peduncle hair type
    the hairs on the peduncles appear tangled or woolly
    Peduncle hairs
    the peduncles are hairy
    Peduncle orientation
    the flower heads are held upright, or slightly angled outwards
    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 a cycle of much smaller bracts outside the cycle of larger and longer bracts
    Style branch number
    the style has two branches

  • Fruits or seeds

    Ovary beak length
    0 mm
    Ovary length in developed fruit
    4–5 mm
    Seed hair tuft bases
    the pappus hairs are attached to one another near the base
    Seed hair tuft color
    the pappus hairs are pale red to red-brown or purple
    Seed hair tuft details
    • the pappus hairs are hooked or barbed
    • the pappus hairs have smaller hairs along their sides
    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 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

  • 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
    Leaf arrangement
    • alternate: there is one leaf per node along the stem
    • basal: the leaves are growing only at the base of the plant
    Leaf blade base
    • the leaf has a distinct petiole
    • 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 bloom
    NA
    Leaf blade edges
    the edge of the leaf blade has teeth
    Leaf blade hairs
    the leaf blade has tangled or woolly-looking hairs
    Leaf blade length
    100–600 mm
    Leaf blade shape
    the leaf blade is oblong (rectangular but with rounded ends)
    Leaf blade tip
    • the tip of the leaf blade is acuminate (tapers to a long, thin point)
    • the tip of the leaf blade is acute (sharply pointed)
    • the tip of the leaf blade is obtuse (bluntly pointed)
    Leaf blade veins
    the leaf blade has one main vein running from the base towards the tip
    Leaf blade width
    Up to 300 mm
    Leaf disposition
    the leaves are nearly similar in size, prominence of teeth, and length of stalks throughout the stem
    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 tufts in axils
    there are no clusters of smaller leaves
    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

  • Place

    Habitat
    terrestrial
    New England state
    • Connecticut
    • Massachusetts
    • Rhode Island
    • Vermont
    Specific habitat
    • man-made or disturbed habitats
    • meadows or fields

  • Stem, shoot, branch

    Flowering stem cross-section
    the flowering stem has strong or sharp angles, but is not square
    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
    at least some of the hairs on the stem are tangled, matted or woolly
    Stem internode hairs
    the stem has 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
absent
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. acanthium

Massachusetts
not applicable (S-rank: SNA)

Subspecies and varieties

Our subspecies is Onopordum acanthium L. ssp. acanthium.

From Flora Novae Angliae dichotomous key

1.  Onopordum acanthium L. ssp. acanthium E

Scotch cotton-thistle. CT, MA, RI, VT. Fields, roadsides, waste areas.

Native to North America?

No

Sometimes confused with

Cirsium vulgare:
pappus bristles plumose, +/- white, 20-30 mm long (vs. O. acanthium, with pappus bristles minutely barbellate, pale red, 7-9 mm long).
Carduus acanthoides:
receptacle flat to conic, not fleshy, shallowly pitted, densely bristly setose between the disk flowers, pappus +/- white (vs. O. acanthium, with the receptacle flat, fleshy, deeply pitted with polygonal depressions that are dentate or short setose around the margins, lacking elongate bristles between the disk flowers, and pappus pale red).

Family

Asteraceae

Genus

Onopordum