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• Cirsium muticum

Cirsium muticum — swamp thistle

Facts

Swamp thistle is a native thistle of wetland margins and saltmarsh margins. The swamp metalmark butterfly lays its eggs on this species, and the catepillar dines exclusively on it.

Habitat

Brackish or salt marshes and flats, marshes, shores of rivers or lakes, wetland margins (edges of wetlands)

Characteristics

• Flowers

  Bases of bract appendages

  NA

  Bract cycle number

  there are three or more cycles of bracts

  Bract inner side hairs

  the bracts are hairy on their inner surfaces

  Bract outer side hair type

  the bracts are hairy, with simple hairs on their outer surface

  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)

  Bract spines

  • the bracts have no spines
  • there is just one simple spine at the tip of the bract

  Bract tip extension appearance

  NA

  Bract tip extension edge

  there are no projections from the bract tips

  Bract tip shape

  • the tips of the bracts acute (have a sharp point)
  • the tips of the bracts are obtuse (have a blunt point)

  Disk flower color

  • blue to purple
  • white

  Disk flower lobe number

  5

  Disk flower proportions

  • 31-45%
  • 46-75%

  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

  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 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

  20–50 mm

  Inflorescence branching (Solidago)

  NA

  Inflorescence shape

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

  Ovary attachment

  the ovary is attached at or near 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 lines or ribs

  there are no lines or ribs visible on the ovary

  Ovary profile

  • in profile, the ovary is oblong (roughly rectangular but rounded at the ends)
  • 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

  0–150 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

  Rim at top of ovary

  the central flowers have a disk-shaped platform above the ovary

  Scale tip

  NA

  Smaller bracts at base of bracts

  there is no smaller, outer cycle of bracts

  Width of flower head base

  10–30 mm

• Fruits or seeds

  Number of pappus parts

  11 or more

  Ovary length in developed fruit

  4.5–5.5 mm

  Seed hair tuft bases

  the pappus hairs are attached to one another near the base

  Seed hair tuft details

  the pappus hairs have smaller hairs along their sides

  Seed hair tuft length

  12–20 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

  Bract resin

  the bracts have 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

  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
  • the underside 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
  • the leaf has no petiole and at the base it clasps the stem, or goes all the way around the stem so the stem appears to pierce the leaf

  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

  • the underside of the leaf has no noticeable bloom
  • there is a noticeable powdery or waxy bloom on the underside of the leaf

  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 tangled or woolly-looking hairs

  Leaf blade length

  150–550 mm

  Leaf blade shape

  • the leaf blade is elliptic (widest near the middle and tapering at both ends)
  • the leaf blade is obovate (egg-shaped, but with the widest point above the middle of the leaf blade)
  • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)

  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

  40–200 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

• Place

  Habitat

  • terrestrial
  • wetlands

  New England state

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

  Specific habitat

  • brackish or salt marshes and flats
  • edges of wetlands
  • marshes
  • shores of rivers or lakes

• 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 length

  At least 0 mm

  Stem internode hair type

  • at least some of the hairs on the stem are tangled, matted or woolly
  • the stem has no hairs between the nodes

  Stem internode hairs

  • the stem has hairs between the nodes
  • the stem has no hairs between the nodes

  Stem wings

  the stem does not have wings on it

Wetland status

Occurs only in wetlands. (Wetland indicator code: OBL)

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae