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• Hymenoxys odorata

Hymenoxys odorata — poison rubberweed

Facts

Poison rubberweed is a southwestern species, unlikely to persist where it has been collected in Maine. It is poisonous to cattle, but sometimes eaten by them when other forage is scarce. Poison rubberweed is said to have contributed to the decline of sheep ranching in the Soutwestern United States.

Habitat

Anthropogenic (man-made or disturbed habitats)

Characteristics

• Flowers

  Bract cycle number

  there are two main cycles of bracts

  Bract outer side hair type

  • the bracts are hairy, with simple hairs on their outer surface
  • the bracts are not hairy on their outer surface

  Bract outer side hairs

  • the bracts are hairy on their outer surfaces
  • the bracts are not hairy on their outer surfaces

  Bract separation

  at least some flower heads have bracts connected to one another at or near their bases

  Bract shape

  • the main bracts are oblanceolate (widest near the tip, but otherwise narrow and tapering)
  • the main bracts are obovate (roughly egg-shaped, but widest near the tip)

  Bract tip shape

  the tips of the bracts are obtuse (have a blunt point)

  Bracts

  there are at least two distinct forms of bracts in different 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

  7–12.5 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 no bristles or papery scales

  Flower head profile

  • the disk is conical across the top
  • the disk is flat or nearly flat across the top
  • the disk is rounded 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

  Height of flower head base

  6–10 mm

  Inflorescence shape

  • the inflorescence is flat-topped in profile
  • 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 has five or more corners in cross-section

  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 lance-shaped, but widest above the middle

  Peduncle hairs

  the peduncles are hairy

  Peduncle length

  2–12 mm

  Ray flower color

  • orange
  • yellow

  Ray flower reproductive parts

  the ray flowers have carpels or stamens, but not both

  Ray flowers

  • 1-5
  • 11-15
  • 16-25
  • 6-10

  Ray length

  8.5–11 mm

  Reproductive system

  all the flowers on the plant contain both carpels and stamens

  Style branches

  the style branch is wider at the tip and has a flattened end, or the style branches are wider at the tips and have flattened ends

  Width of flower head base

  7–12.5 mm

• Fruits or seeds

  Number of pappus parts

  • 10
  • 5
  • 6
  • 7
  • 8
  • 9

  Ovary length in developed fruit

  1.7–2.5 mm

  Seed hair tuft length

  1.6–2.3 mm

  Seed hair tuft tips

  the pappus hairs are slender

  Seed hairs uniform

  all the pappus hairs are approximately the same length

  Seed tuft scale number

  5–6

  Seed tuft type

  the pappus is made of flat scales that are not split or frayed at the tips

  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 resin or resin glands

  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 annual, it lacks evidence of previous years' growth

  Spines on plant

  the plant has no spines

• 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

  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 hairs

  the leaf blade has hairs with glands at their tips

  Leaf blade length

  10–50 mm

  Leaf blade shape

  the leaf blade is linear (very narrow with more or less parallel sides)

  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 one main vein running from the base towards the tip

  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 type

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

  Specific leaf type

  the leaf has a row of two or more lobes on each side of the central axis

• Place

  Habitat

  terrestrial

  New England state

  Maine

  Specific habitat

  man-made or disturbed habitats

• Scent

  Plant odor

  the plant has a pleasant odor, such as licorice, fruit or resin

• Stem, shoot, branch

  Leaves on stem

  there is at least one full leaf above the base of the flowering stem

  Stem internode hair direction

  • NA
  • 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
  • the stem has no hairs between the nodes

  Stem internode hairs

  • the stem has hairs between the nodes
  • the stem has no hairs between the nodes

  Stem wings

  the stem does not have wings on it

Wetland status

Not classified

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae