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• Dichotomous Key
• Asteraceae
• Asteraceae Group 6
• Helianthus
• Helianthus annuus

Helianthus annuus — common sunflower

Facts

Common sunflower is the only plant species native to North America to become a worldwide crop of economic importance. Its current distribution reflects escaped cultivars, and it is considered introduced in New England. All parts of the wild plant were used by native Americans for food, medicinal and ceremonial purposes.

Habitat

Anthropogenic (man-made or disturbed habitats), meadows and fields

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 oblong (roughly rectangular but rounded at the ends)
  • the main bracts are ovate (egg-shaped)

  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)

  Bract width

  3–8

  Disk flower color

  • blue to purple
  • pink to red
  • yellow

  Disk flower lobe number

  5

  Disk flower number

  more than 50

  Disk flower reproductive parts

  the disk flower has both pollen- and seed-producing parts

  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 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 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

  20–100

  Ovary cross-section

  the ovary is compressed (flattened)

  Ovary hairs

  • the ovary has hairs on it
  • the ovary has no hairs on it

  Peduncle length

  20–200 mm

  Ray flower color

  yellow

  Ray flower reproductive parts

  there are neither carpels nor stamens in the ray flowers

  Ray flowers

  • 11-15
  • 16-25
  • 26-50
  • more than 50

  Ray length

  25–30 mm

  Width of flower head base

  15–200 mm

• Fruits or seeds

  Number of pappus parts

  • 2
  • 3
  • 4
  • 5
  • 6

  Ovary length in developed fruit

  3–15 mm

  Ovary width in developed fruit

  4–8 mm

  Seed hair tuft bases

  NA

  Seed hair tuft color

  NA

  Seed hair tuft details

  NA

  Seed hair tuft length

  0.5–3.5 mm

  Seed hair tuft tips

  NA

  Seed hairs uniform

  NA

  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

  Leaf blade glands

  • the leaf blades have glandular (translucent) dots or scales
  • 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 annual, it lacks evidence of previous years' growth

  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

  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)
  • the base of the leaf is cordate (heart-shaped) or sagittate (arrow-shaped)

  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

  100–400 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)
  • the leaf blade is triangular, with the stalk or attachment point on one of the sides

  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 acute (sharply pointed)

  Leaf blade veins

  the leaf blade has three main veins running from the base towards the tip

  Leaf blade width

  50–250 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

  20–200 mm

  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

• 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

  there is no powdery or waxy film on the stem

  Stem internode hairs

  the stem has 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

From the dichotomous key of Flora Novae Angliae