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

Helianthus giganteus — tall sunflower

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Facts

Tall sunflower is not misnamed as this perennial is a true giant, potentially reaching 13 feet in height. This species is one of several wild sunflowers that could be important sources of disease resistance in cultivated sunflower (Helianthus annuus). However, the wild species cross poorly with the cultivar, leading to development of novel methods to generate crosses (protoplast fusion).

Habitat

Anthropogenic (man-made or disturbed habitats), meadows and fields, wetland margins (edges of wetlands)

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
  • wetlands
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • 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 no teeth or lobes
  • 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
70–200 mm
Disk flower number
more than 50
Show all characteristics

  • Flowers

    Bract cycle number
    • there are three or more cycles of bracts
    • there are two main cycles of bracts
    Bract margins
    there are fine hairs along the bract margins
    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)
    Bract spines
    the bracts have no spines
    Bract tip orientation
    the bracts are pressed against the plant, or spreading out at the tips
    Bract tip shape
    the tips of the bracts are acuminate (tapered to a narrow point)
    Bracts
    the bracts in separate cycles are similar or gradually changing from the outer to inner cycles
    Disk flower color
    yellow
    Disk flower number
    more than 50
    Disk flower reproductive parts
    the disk flower has both pollen- and seed-producing parts
    Disk width
    15–25 mm
    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 papery scales on it
    Flower head profile
    the disk is rounded across the top
    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
    Inflorescence shape
    the inflorescence is not flat-topped but appears rounded, with some flower heads distinctly higher than others
    Ovary beak
    there is no beak on the ovary
    Ovary cross-section
    the ovary is compressed (flattened)
    Ovary hair type
    • the ovary has hairs on it, but the hairs have no glands
    • the ovary has no hairs on it
    Ovary hairs
    • the ovary has hairs on it
    • the ovary has no hairs on it
    Ovary profile
    in profile, the ovary is another shape
    Ray flower color
    yellow
    Ray flower reproductive parts
    there are neither carpels nor stamens in the ray flowers
    Ray flowers
    • 11-15
    • 16-25
    • 6-10
    Ray length
    15–25 mm
    Reproductive system
    all the flowers on the plant contain both carpels and stamens
    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
    the style has two branches
    Width of flower head base
    10–24 mm

  • Fruits or seeds

    Number of pappus parts
    2
    Ovary length in developed fruit
    3–5 mm
    Seed hair tuft bases
    NA
    Seed hair tuft color
    NA
    Seed hair tuft details
    NA
    Seed hair tuft length
    1–5 mm
    Seed hair tuft tips
    NA
    Seed hairs uniform
    all the pappus hairs are approximately the same length
    Seed tuft scale number
    2–6
    Seed tuft type
    • the pappus is made of flat scales that are not split or frayed at the tips
    • the pappus is made of stiff, tapering bristles
    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

    Bract resin
    the bracts have no resin or resin glands

  • 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
    there is a thickened taproot 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
    • opposite: there are two leaves per node along the stem
    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 no teeth or lobes
    • the edge of the leaf blade has teeth
    Leaf blade flatness
    the leaf is flat (planar) at the edges
    Leaf blade length
    70–200 mm
    Leaf blade shape
    • the leaf blade is lanceolate (lance-shaped; widest below the middle and tapering at both ends)
    • the leaf blade is oblong (rectangular but with rounded ends)
    • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)
    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 three main veins running from the base towards the tip
    Leaf blade width
    10–90 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
    • the leaves have no leaf stalks, but attach directly to the stem
    Leaf stalk length
    3–15 mm
    Leaf type
    leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
    Specific leaf type
    the leaves are simple (i.e., lobed or unlobed but not separated into leaflets

  • Place

    Habitat
    • terrestrial
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • Vermont
    Specific habitat
    • edges of wetlands
    • man-made or disturbed habitats
    • meadows or fields

  • 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 internode hair direction
    the hairs point mostly upwards to outwards
    Stem internode hair type
    the hairs on the stem are plain, without glands or branches, and not tangled
    Stem internode hairs
    • the stem has hairs between the nodes
    • the stem has no hairs between the nodes

Wetland status

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

In New England

Distribution

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

Conservation status

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

Massachusetts
not applicable (S-rank: SNA)

From Flora Novae Angliae dichotomous key

5.  Helianthus giganteus L. E

tall sunflower. Helianthus alienus E.E. Wats.; H. borealis E.E. Wats.; H. giganteus L. ssp. alienus (E.E. Wats.) R.W. Long; H. giganteus L. var. subtuberosus Britt.; H. subtuberosus (Britt.) Britt.; 
 H. validus E.E. Wats. • CT, MA, ME, VT; also reported from RI by George (1997), but specimens are unknown. Fields, borders of brackish marshes, disturbed soil.

5×6. Helianthus giganteus × Helianthus grosseserratus → Helianthus ×‌luxurians E.E. Wats. is a very rare hybrid sunflower known from CT, MA. It closely resembles its parental species. It shows ± glabrous and glaucous stems, and variably toothed leaf blades (subentire to coarsely toothed) that are usually 5–10 times as long as wide and borne on short petioles 5–10 mm long.

Native to North America?

Yes and no (some introduced)

Sometimes confused with

Helianthus divaricatus:
well-developed leaves sessile, with rounded to cordate bases, and capitula with 8-12 ray flowers (vs. H. giganteus, with well-developed leaves with petioles 0-12 mm long, with cuneate bases, and capitula with 12-20 ray flowers).
Helianthus grosseserratus:
lobes of the disk corollas glabrous or glabrate, anther appendages yellow, and leaf blades slightly, if at all, scabrous on the adaxial surface (vs. H. giganteus, with lobes of the disk corollas pubescent, anther appendages red-brown to dark brown, and leaf blades strongly scabrous on the adaxial surface).

Synonyms

  • Helianthus alienus E.E. Wats.
  • Helianthus borealis E.E. Wats.
  • Helianthus giganteus L. ssp. alienus (E.E. Wats.) R.W. Long
  • Helianthus giganteus L. var. subtuberosus Britt.
  • Helianthus subtuberosus (Britt.) Britt.
  • Helianthus validus E.E. Wats.

Family

Asteraceae

Genus

Helianthus