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Native Plant Trust: Go Botany Discover thousands of New England plants

Hieracium pilosella — mouse-ear hawkweed

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Facts

Mouse-ear hawkweed is native to Europe and introduced to eastern and northwestern North America, where it is considered a noxious weed in some states. It reproduces both clonally by stolons, and by seed, and establishes well in low-nutrient and overgrazed situations.

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
  • the leaves are growing only at the base of the plant (basal)
Leaf blade edges
the edge of the leaf blade has no teeth or lobes
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
yellow
Tuft or plume on fruit
at least a part of the plume is made up of fine bristles
Spines on plant
the plant has no spines
Leaf blade length
10–75 mm
Disk flower number
0
Show all characteristics

  • Flowers

    Bases of bract appendages
    NA
    Bract outer side hairs
    the bracts are hairy on their outer surfaces
    Bract tip shape
    • the tips of the bracts acute (have a sharp point)
    • the tips of the bracts are acuminate (tapered to a narrow point)
    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 only one to three 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 head profile
    the disk is flat or nearly flat across the top
    Flower head shape
    the flower head is hemispherical (like the bottom half of a sphere)
    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
    7.5–10 mm
    Inflorescence branching (Solidago)
    NA
    Number of bracts at flower head base
    20–34
    Ovary beak
    there is no beak on the ovary
    Ovary cross-section
    the ovary has five or more corners in cross-section
    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 seven to nine ribs visible on the ovary
    • there are ten or more ribs visible on the ovary
    Peduncle hair type
    the hairs on the peduncles are branched
    Peduncle hairs
    the peduncles are hairy
    Ray flower color
    yellow
    Ray flower reproductive parts
    the ray flowers have both carpels and stamens
    Ray flowers
    more than 50
    Ray length
    8–13 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
    there are no obvious branches on the style

  • Fruits or seeds

    Dispersal unit
    the seeds fall off or are dispersed separately from one another
    Number of pappus parts
    11 or more
    Ovary beak length
    0 mm
    Ovary length in developed fruit
    1.5–2 mm
    Ovary width in developed fruit
    0.3–0.5 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
    4–5 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

    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 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
    the plant has no spines
    Underground organs
    there is a thickened taproot on the plant

  • Leaves

    Final leaf segment length (compound lvs only)
    0 mm
    Final leaf segment width (compound lvs only)
    0 mm
    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
    • the leaves are growing only at the base of the plant (basal)
    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
    • 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 no teeth or lobes
    Leaf blade hairs
    • the leaf blade has branched hairs
    • the leaf blade has simple hairs with no glands, and not tangled or wooly
    Leaf blade length
    10–75 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 surface colors
    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)
    • the tip of the leaf blade is obtuse (bluntly pointed)
    Leaf blade width
    5–18 mm
    Leaf disposition
    the lower leaves are larger, toothier, and/or on longer stalks than the upper leaves
    Leaf spines
    there are no spines on 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 (lobed or unlobed but not separated into leaflets)
    Leaflet number
    0
    Specific leaf type
    the leaves are simple (lobed or unlobed but not separated into leaflets
    Teeth per side of leaf blade
    0

  • 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
    the flowering stem has no leaves above the base
    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
    the hairs point mostly upwards to outwards
    Stem internode hair length
    1–3 mm
    Stem internode hair type
    • at least some of the hairs on the stem are branched
    • at least some of the hairs on the stem have glands
    Stem internode hairs
    the stem has hairs between the nodes
    Stem wings
    the stem does not have wings on it

Wetland status

Not classified

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)

var. niveum

Massachusetts
unranked (S-rank: SNR)

var. pilosella

Massachusetts
unranked (S-rank: SNR)

From Flora Novae Angliae dichotomous key

10.  Hieracium pilosella L. E

mouse-ear hawkweed. Hieracium pilosella L. var. niveum Muell.-Arg.; Pilosella officinarum
F.W. Schultz & Schultz-Bip. • CT, MA, ME, NH, RI, VT. Open areas such as lawns, fields, and roadsides.

Native to North America?

No

Sometimes confused with

Hieracium flagellare:
stems with mostly 2-4 flower heads and series of involucral bracts mostly 10-13 mm tall (vs. H. pilosella, with stems with mostly 1 or 2 flower heads and series of involucral bracts mostly 7.5-9 mm tall).

Synonyms

  • Hieracium pilosella L. var. niveum Muell.-Arg.
  • Pilosella officinarum F.W. Schultz & Schultz-Bip.

Family

Asteraceae

Genus

Hieracium