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• Asteraceae
• Asteraceae Group 6
• Helianthus
• Helianthus microcephalus

Helianthus microcephalus — small-headed sunflower

Facts

The small-headed sunflower, true to its name, has smaller flower heads than the other sunflower species, an inch or less in diameter. Its natural range does not extend into New England, but it is often grown in gardens.

Habitat

Anthropogenic (man-made or disturbed habitats)

Characteristics

• Flowers

  Bract cycle number

  • there are three or more cycles of bracts
  • there are two main cycles of bracts

  Bract inner side hairs

  the bracts are not hairy on their inner surfaces

  Bract margins

  there are fine hairs along the bract margins

  Bract outer side hair type

  the bracts are not hairy on their outer surface

  Bract outer side hairs

  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 orientation

  the bracts are pressed against the plant, or spreading out at the tips

  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)

  Bracts

  the bracts in separate cycles are similar or gradually changing from the outer to inner cycles

  Disk flower color

  yellow

  Disk flower number

  • 11-20
  • 21-50

  Disk flower reproductive parts

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

  Disk width

  4–10 mm

  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

  Height of flower head base

  7–10 mm

  Inflorescence branching (Solidago)

  NA

  Ovary beak

  there is no beak on the ovary

  Ovary cross-section

  the ovary is compressed (flattened)

  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
  • 6-10

  Ray length

  10–15 mm

  Reproductive system

  some of the flowers on the plant have only carpels or stamens, while others have both carpels and stamens

  Style branch number

  the style has two branches

  Width of flower head base

  6–13 mm

• Fruits or seeds

  Number of pappus parts

  2

  Ovary length in developed fruit

  3.5–4.2 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

  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

• 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 caudex (the root mass is firm and hardened at the top)
  • the plant has a rhizome (a horizontal underground stem with roots growing from it)
  • there are only slender roots 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

  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 hairs

  the leaf blade has simple hairs with no glands, and not tangled or wooly

  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 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)

  Leaf blade veins

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

  Leaf blade width

  10–60 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

  5–25 mm

  Leaf type

  leaves are simple (lobed or unlobed but not separated into leaflets)

  Specific leaf type

  the leaves are simple (lobed or unlobed but not separated into leaflets

• Place

  Habitat

  terrestrial

  New England state

  Connecticut

  Specific habitat

  man-made or disturbed habitats

• 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

  Stem internode hair direction

  NA

  Stem internode hair type

  the stem has no hairs between the nodes

  Stem internode hairs

  the stem has no hairs between the nodes

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