Helianthus decapetalus L.

thin-leaved sunflower

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New England Distribution

Adapted from BONAP data

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North America Distribution

Adapted from BONAP data

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Facts About

The seeds of thin-leaved sunflower are eaten by gamebirds and songbirds. Muskrats eat the leaves and stems and use the stems in the construction of their lodges. The Meskwaki applied a poultice of the macerated roots to persistent sores.

Habitat

Floodplain (river or stream floodplains), forest edges, forests

Characteristics

Habitat
terrestrial
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf type
leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
Leaf arrangement
  • alternate: there is one leaf per node along the stem
  • opposite: there are two leaves per node along the stem
Leaf blade edges
the edge of the leaf blade has teeth
Flower type in flower heads
the flower head has tubular disk flowers in the center and ray flowers, these often strap-shaped, around the periphery
Ray flower color
yellow
Tuft or plume on fruit
there is no plume, or the plume is made up of scales, awns, a crown, or a rim
Spines on plant
the plant has no spines
Leaf blade length
70–210 mm
Disk flower number
21-50
Show All Characteristics
  • Flowers
    Bases of bract appendages
    NA
    Bract margins
    there are fine hairs along the bract margins
    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)
    • the main bracts are linear (long and very narrow)
    Bract tip shape
    the tips of the bracts are acuminate (tapered to a narrow point)
    Bract width
    2–3
    Disk flower color
    yellow
    Disk flower lobe number
    5
    Disk flower number
    21-50
    Disk flower reproductive parts
    the disk flower has both pollen- and seed-producing parts
    Disk width
    10–20 mm
    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, each flower has a single enlarged lobe or strap
    Flower head platform
    the base has papery scales on it
    Flower head shape
    the flower head is hemispherical (like the bottom half of a sphere)
    Flower type in flower heads
    the flower head has tubular disk flowers in the center and ray flowers, these often strap-shaped, around the periphery
    Inflorescence branching (Solidago)
    NA
    Number of bracts at flower head base
    20–25
    Ovary cross-section
    the ovary is compressed (flattened)
    Peduncle length
    20–120 mm
    Ray flower color
    yellow
    Ray flower reproductive parts
    there are neither carpels nor stamens in the ray flowers
    Ray flowers
    • 11-15
    • 6-10
    Ray length
    20–25 mm
    Width of flower head base
    12–25 mm
  • Fruits or seeds
    Number of pappus parts
    2
    Ovary length in developed fruit
    3.5–5 mm
    Seed hair tuft bases
    NA
    Seed hair tuft color
    NA
    Seed hair tuft details
    NA
    Seed hair tuft length
    3–4 mm
    Seed hair tuft tips
    NA
    Seed hairs uniform
    NA
    Seed tuft scale number
    2
    Seed tuft type
    the pappus is made of flat scales that are not split or frayed at the tips
    Top of disk flower ovary
    NA
    Tuft or plume on fruit
    there is no plume, or the plume is made up of scales, awns, a crown, or a rim
  • Glands or sap
    Leaf blade glands
    the leaf blades have 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 perennial, it shows evidence of previous year's leaves, stems or stem bases
    Spines on plant
    the plant has no spines
    Underground organs
    the plant has a rhizome (a horizontal underground stem with roots growing from it)
  • 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
    Leaf arrangement
    • alternate: there is one leaf per node along the stem
    • opposite: there are two leaves per node along the stem
    Leaf blade base
    the leaf has a distinct 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
    • the base of the leaf blade is rounded
    • the base of the leaf blade is truncate (ends abruptly in a more or less straight line as though cut off)
    Leaf blade bloom
    the underside of the leaf has no noticeable bloom
    Leaf blade edges
    the edge of the leaf blade has teeth
    Leaf blade length
    70–210 mm
    Leaf blade shape
    • the leaf blade is lanceolate (lance-shaped; widest below the middle and tapering at both ends)
    • 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 tip
    • the tip of the leaf blade is acuminate (tapers to a long, thin point)
    • the tip of the leaf blade is rounded, with no point
    Leaf blade veins
    the leaf blade has three main veins running from the base towards the tip
    Leaf blade width
    40–100 mm
    Leaf disposition
    the leaves are nearly similar in size, prominence of teeth, and length of stalks throughout the stem
    Leaf spines
    there are no spines on the leaf edges
    Leaf stalk
    the leaves have leaf stalks
    Leaf stalk length
    15–60 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 leaves are simple (i.e., lobed or unlobed but not separated into leaflets
  • Place
    Habitat
    terrestrial
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • edges of forests
    • forests
    • river or stream floodplains
  • 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
    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)

New England Distribution and Conservation Status

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)

Native to North America?

Yes

Sometimes Confused With

Helianthus strumosus:
involucral bracts at base of flower head ascending, not exceeding the disk of the flower head and leaf stalks 5-30 mm long (vs. H. decapetalus, with the involucral bracts at base of flower head spreading, much longer than the disk of the flower head and leaf stalks 15-60 mm long).
Helianthus tuberosus:
stems evidently hairy and without a bloom and rhizomes ending in thickened tubers (vs. H. decapetalus, with stems without hairs or with very few hairs and with a whitish bloom and rhizomes not ending in thickened tubers).

Synonyms

  • Helianthus tracheliifolius P. Mill.

Family

Asteraceae

Genus

Helianthus

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Information from Dichotomous Key of Flora Novae Angliae

3.  Helianthus decapetalus L. N

thin-leaved sunflower. Helianthus tracheliifolius P. Mill. • CT, MA, ME, NH, RI, VT. Riparian forests, mesic, deciduous forests, forest edges.