Hymenoxys odorata DC.

poison rubberweed

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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

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

Habitat
terrestrial
New England state
Maine
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
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
  • orange
  • 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
10–50 mm
Disk flower number
more than 50
Show All 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 (i.e., 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

Distribution

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

Conservation Status

None

Native to North America?

Yes and no (some introduced)

Sometimes Confused With

Helenium autumnale:
involucral bracts reflexed in fruit, stems winged by decurrent leaf bases, and leaf blades simple (vs. H. odorata, with involucral bracts spreading to erect in fruit, stems unwinged, and larger leaf blades usually pinnately lobed into very narrow segments).

Synonyms

  • Actinella odorata Gray
  • Picradenia odorata (DC.) Britt.

Family

Asteraceae

Genus

Hymenoxys

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Information from Dichotomous Key of Flora Novae Angliae

1.  Hymenoxys odorata DC. E

poison rubberweed. Actinella odorata Gray; Picradenia odorata (DC.) Britt. • ME. Waste 
areas, yards.