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Sonchus arvensis — field sow-thistle

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Facts

Field sow-thistle is native to Eurasia and introduced worldwide. It was first found in Pennsylvania in 1814 and occurs across the United States and Canada in a range of habitat types, including wet and saturated soils. It is considered a noxious weed in many states. There are two varieties in New England. Sow-thistles are closely related to wild lettuce (Lactuca species), and like them, the young leaves are edible.

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
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf type
leaves are simple (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
  • the edge of the leaf blade has no teeth or lobes
  • the edge of the leaf blade has teeth
Flower type in flower heads
the flower head has ray flowers only, meaning all of the individual flowers of the flower head have a strap-shaped ray, which may or may not have teeth at the very tip of the ray
Ray flower color
  • orange
  • yellow
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
30–400 mm
Disk flower number
0
Show all characteristics

  • Flowers

    Bases of bract appendages
    NA
    Bract cycle number
    there are three or more cycles of bracts
    Bract outer side hair type
    • the bracts are hairy on their outer surfaces, with hairs having glands (a swelling at the tip of the hair)
    • the bracts are not hairy on their outer surface
    Bract outer side hairs
    • the bracts are hairy on their outer surfaces
    • the bracts are not hairy on their outer surfaces
    Bract shape
    the main bracts are lanceolate (widest above the base, then taper narrowly towards the tip)
    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 color
    NA
    Disk flower lobe number
    0
    Disk flower number
    0
    Disk flower proportions
    NA
    Disk flower reproductive parts
    NA
    Disk flower shape
    NA
    Flower head number
    each flowering stem has four or more flower heads on it
    Flower head outer flowers
    at the outer edge of the flower head, each flower has a single enlarged lobe or strap
    Flower head platform
    the base has no bristles or papery scales
    Flower head platform surface
    NA
    Flower type in flower heads
    the flower head has ray flowers only, meaning all of the individual flowers of the flower head have a strap-shaped ray, which may or may not have teeth at the very tip of the ray
    Height of flower head base
    14–22 mm
    Inflorescence branching (Solidago)
    NA
    Inflorescence shape
    the inflorescence is flat-topped in profile
    Ovary beak
    there is no beak on the ovary
    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 lance-shaped, but widest above the middle
    • in profile, the ovary is roughly elliptical (widest in the middle, tapering to both ends)
    Ovary surface
    the ovary surface is textured with tiny points, bumps or wrinkles
    Peduncle hair type
    the hairs on the peduncles have glands at their tips
    Peduncle hairs
    • the peduncles are hairy
    • the peduncles have no hairs
    Ray flower color
    • orange
    • yellow
    Ray flower reproductive parts
    the ray flowers have both carpels and stamens
    Ray flowers
    more than 50
    Ray length
    15–25 mm
    Reproductive system
    all the flowers on the plant contain both carpels and stamens
    Rim at top of ovary
    the central flowers have no disk-shaped platform above the ovary
    Scale tip
    NA
    Smaller bracts at base of bracts
    there is no smaller, outer cycle of bracts
    Style branch number
    there are no obvious branches on the style
    Swelling at base of flower head
    the peduncles are not swollen, or only slightly
    Width of flower head base
    8–15 mm

  • Fruits or seeds

    Ovary beak length
    0 mm
    Ovary length in developed fruit
    2.5–3.5 mm
    Ovary width in developed fruit
    0.6–0.7 mm
    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
    8–14 mm
    Seed hair tuft tips
    the pappus hairs are slender
    Seed hairs uniform
    there are two distinct lengths of pappus hairs
    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 milky and opaque, and may be white or colored

  • Growth form

    Growth form
    the plant has one or more free-standing stems
    Horizontal rooting stem
    • there are no stolons
    • there are stolons on some plants
    Plant lifespan
    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
    the plant has a rhizome (a horizontal underground stem with roots growing from it)

  • 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
    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 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 rounded
    Leaf blade 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
    • the edge of the leaf blade has no teeth or lobes
    • the edge of the leaf blade has teeth
    Leaf blade hairs
    • the leaf blade has hairs with glands at their tips
    • the leaf blade has simple hairs with no glands, and not tangled or wooly
    Leaf blade length
    30–400 mm
    Leaf blade shape
    • the leaf blade is elliptic (widest near the middle and tapering at both ends)
    • the leaf blade is lanceolate (lance-shaped; widest below 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)
    • the leaf blade is oblong (rectangular but with rounded ends)
    Leaf blade surface colors
    • there are noticeable spots, patches or stripes on the upper surface of the leaf
    • there is no noticeable color variation on the upper surface of the leaf
    Leaf blade tip
    the tip of the leaf blade is acute (sharply pointed)
    Leaf blade width
    20–150 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 no leaf stalks, but attach directly to the stem
    Leaf tip extension
    NA
    Leaf type
    leaves are simple (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
    • Maine
    • Massachusetts
    • New Hampshire
    • 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
    • the stem has a powdery or waxy film on it that can be rubbed away
    • there is no powdery or waxy film on the stem
    Stem internode hair direction
    NA
    Stem internode hair length
    0 mm
    Stem internode hair type
    the stem has no hairs between the nodes
    Stem internode hairs
    the stem has no hairs between the nodes
    Stem wings
    the stem does not have wings on it

Wetland status

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

In New England

Distribution

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

Conservation status

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

Massachusetts
unranked (S-rank: SNR)

ssp. arvensis

Massachusetts
unranked (S-rank: SNR)

ssp. uliginosus

Massachusetts
unranked (S-rank: SNR)

Subspecies and varieties

Sonchus arvensis L. var. arvensis is the more common form, known from CT, MA, ME, NH, RI, VT.S. arvensis var. glabrescens Guenth., Grab., & Wimmer is known from CT, MA, ME, NH, VT.

From Flora Novae Angliae dichotomous key

1.  Sonchus arvensis L. E

field sow-thistle.  1a. Sonchus arvensis L. ssp. uliginosus (Bieb.) Nyman; S. uliginosus Bieb. 
• CT, MA, ME, NH, RI, VT. Fields, roadsides, pastures, waste areas.

1a.  Peduncles and involucres glabrous (though sometimes with sessile yellow glands on the involucre); longer involucral bracts 10–15 mm long 
 … 1a. S. arvensis var. glabrescens Guenth., Grab., & Wimmer

1b.  Peduncles and involucres pubescent with yellow, glandular-hairs; longer involucral bracts 14–17 mm long … 1b. S. arvensis var. arvensis

Variety glabrescens is known from CT, MA, ME, NH, VT. It is less common than typical variety. Variety arvensis is known from CT, MA, ME, NH, RI, VT.

Native to North America?

No

Sometimes confused with

Sonchus oleraceus:
flower heads 1.5-2.5 cm wide and plants annual from a taproot (vs. S. arvensis, with flower heads 3-5 cm wide and plants perennial from a deep-seated rhizome).

Family

Asteraceae

Genus

Sonchus