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• Asteraceae
• Asteraceae Group 2
• Onopordum
• Onopordum acanthium

Onopordum acanthium — Scotch cotton-thistle

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

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

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae