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• Dichotomous Key
• Asteraceae
• Asteraceae Group 2
• Cirsium
• Cirsium palustre

Cirsium palustre — marsh thistle

Facts

A European native, and highly invasive in North America, marsh thistle can displace native wetland flora as it forms dense stands. Its range is currently limited, but it is rapidly expanding.

Habitat

Marshes, swamps, wetland margins (edges of wetlands)

Characteristics

• Flowers

  Bract color

  the bracts are colored, or at least tinged with, pink, red or purple

  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 on their outer surfaces, with curled, tangled, matted, or woolly hairs

  Bract outer side hairs

  the bracts are 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 linear (long and very narrow)
  • the main bracts are ovate (egg-shaped)

  Bract spines

  • the bracts have no 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 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)

  Bracts

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

  Disk flower number

  • 21-50
  • more than 50

  Disk flower reproductive parts

  • the disk flower has both pollen- and seed-producing parts
  • the disk flower has either only pollen- or only 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 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 flat or nearly flat across the top
  • the disk is rounded 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

  10–20 mm

  Inflorescence branching (Solidago)

  NA

  Inflorescence shape

  the inflorescence is not flat-topped but appears rounded, with some flower heads distinctly higher than others

  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 lines or ribs

  there are no lines or ribs visible on the ovary

  Ovary profile

  in profile, the ovary is roughly egg-shaped

  Peduncle length

  0–10 mm

  Ray flower color

  NA

  Ray flower reproductive parts

  NA

  Ray flowers

  0

  Ray length

  0 mm

  Reproductive system

  • all the flowers on some plants have carpels, while all the flowers on other plants have stamens
  • 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

  8–13 mm

• Fruits or seeds

  Ovary length in developed fruit

  2.5–3.5 mm

  Seed hair tuft details

  the pappus hairs have smaller hairs along their sides

  Seed hair tuft length

  9–11 mm

  Seed hairs uniform

  all the pappus hairs are approximately the same length

  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

  Bract resin

  the bracts have no resin or resin glands

  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 biennial, it appears as either first year (non-reproductive) plants or second year plants with flowers or fruit
  • the plant is perennial, it shows evidence of previous year's leaves, stems or stem bases

  Spines on plant

  there are spines on the plant

  Underground organs

  there are only slender roots 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 edges

  • the edge of the leaf blade has lobes, or it has both teeth and lobes
  • the edge of the leaf blade has teeth

  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

  150–300 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 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)

  Leaf blade veins

  the leaf blade has one main vein running from the base towards the tip

  Leaf blade width

  30–100 mm

  Leaf disposition

  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 tip extension

  NA

  Leaf type

  leaves are simple (i.e., 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 leaves are simple (i.e., lobed or unlobed but not separated into leaflets

• Place

  Habitat

  wetlands

  New England state

  • Massachusetts
  • New Hampshire

  Specific habitat

  • edges of wetlands
  • marshes
  • swamps

• 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

  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

Usually occurs in wetlands, but occasionally in non-wetlands. (Wetland indicator code: FACW)

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae