Eupatorium torreyanum Short & Peter

Torrey's thoroughwort

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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

Torrey's thoroughwort is endangered in Connecticut, the only New England state where it is found.

Habitat

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

Characteristics

Habitat
terrestrial
New England state
Connecticut
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
  • whorled: there are three or more leaves per node along the stem
Leaf blade edges
the edge of the leaf blade has teeth
Flower type in flower heads
the flower head has disk flowers only, and lacks the strap-shaped flowers
Ray flower color
NA
Tuft or plume on fruit
at least a part of the plume is made up of fine bristles
Spines on plant
the plant has no spines
Leaf blade length
20–60 mm
Disk flower number
1-5
Show All Characteristics
  • Flowers
    Bract color
    the bracts are not colored or tinged with pink, red or purple
    Bract cycle number
    • there are three or more cycles of bracts
    • there are two main cycles of bracts
    Bract keels
    the bracts do not have keels
    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 elliptic (widest near the middle and tapered towards the base and tip)
    • the main bracts are oblong (roughly rectangular but rounded at the ends)
    Bract spines
    the bracts have no spines
    Bract tip color
    the tips are a different color from the center of the bract
    Bract tip shape
    • the tips of the bracts acute (have a sharp point)
    • the tips of the bracts are obtuse (have a blunt point)
    • the tips of the bracts are rounded
    Bract width
    1–1.5
    Bracts
    there are at least two distinct forms of bracts in different cycles
    Disk flower color
    white
    Disk flower lobe number
    5
    Disk flower number
    1-5
    Disk flower reproductive parts
    the disk flower has both pollen- and seed-producing parts
    Disk flower shape
    the disk flower is tube-shaped (cylindrical), or gradually widening like a funnel
    Flower head outer flowers
    at the outer edge of the flower head, the flowers have no enlarged lobe or strap, and are of similar size as those in the center of the disk
    Flower head platform
    the base has no bristles or papery scales
    Flower head platform surface
    NA
    Flower head profile
    • the disk is flat or nearly flat across the top
    • the disk is rounded across the top
    Flower head shape
    the sides of the flower head diverge like a funnel
    Flower type in flower heads
    the flower head has disk flowers only, and lacks the strap-shaped flowers
    Height of flower head base
    4–7 mm
    Inflorescence branching (Solidago)
    NA
    Inflorescence shape
    the inflorescence is flat-topped in profile
    Inflorescence stem
    hairs are present on the stem of the inflorescence
    Number of bracts at flower head base
    8–10
    Ovary cross-section
    the ovary has five or more corners in cross-section
    Ovary hair type
    the ovary has no hairs on it
    Ovary hairs
    the ovary has no hairs on it
    Ovary lines or ribs
    there are four to six lines or ribs visible on the ovary
    Peduncle hairs
    the peduncles are hairy
    Ray flower color
    NA
    Ray flower reproductive parts
    NA
    Ray flowers
    NA
    Ray length
    0 mm
    Reproductive system
    all the flowers on the plant contain both carpels and stamens
    Scale tip
    NA
    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
    1–6 mm
  • Fruits or seeds
    Number of pappus parts
    11 or more
    Ovary length in developed fruit
    2–3 mm
    Seed hair tuft color
    the pappus hairs are white or off-white
    Seed hair tuft details
    the pappus hairs are hooked or barbed
    Seed hair tuft length
    3.5–4 mm
    Seed hairs uniform
    all the pappus hairs are approximately the same length
    Seed tuft scale number
    0
    Seed tuft type
    the pappus is made of very fine hairs or bristles
    Top of disk flower ovary
    NA
    Tuft or plume on fruit
    at least a part of the plume is made up of fine bristles
  • Glands or sap
    Leaf blade glands
    the leaf blades have glandular (translucent) dots or scales
    Ovary glands
    there are glands on the ovary surface
    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 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)
  • 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
    Hairs on upper side of leaf blade
    the upper side 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
    • whorled: there are three or more leaves per node along the stem
    Leaf blade base
    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 bloom
    NA
    Leaf blade edges
    the edge of the leaf blade has teeth
    Leaf blade flatness
    NA
    Leaf blade hairs
    NA
    Leaf blade length
    20–60 mm
    Leaf blade shape
    • the leaf blade is lanceolate (lance-shaped; widest below the middle and tapering at both ends)
    • the leaf blade is linear (very narrow with more or less parallel 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 acute (sharply pointed)
    Leaf blade veins
    the leaf blade has one main vein running from the base towards the tip
    Leaf blade width
    5–17 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 no leaf stalks, but attach directly to the stem
    Leaf stalk length
    At least 0 mm
    Leaf tufts in axils
    there are clusters of smaller leaves growing out of axils
    Leaf type
    leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
    Leaflet number
    0
    Specific leaf type
    the leaves are simple (i.e., lobed or unlobed but not separated into leaflets
  • Place
    Habitat
    terrestrial
    New England state
    Connecticut
    Specific habitat
    • 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 bloom
    there is no powdery or waxy film on the stem
    Stem internode hair direction
    the hairs are pressed flat against the plant, pointing either towards the plant's tip or towards it's base
    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
    Stem wings
    the stem does not have wings on it

Wetland Status

Not classified

New England Distribution and Conservation Status

Distribution

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

Conservation Status

None

Native to North America?

Yes

Sometimes Confused With

Eupatorium hyssopifolium:
leaves usually 4 per node, with blades mostly 0.5–5, entire or irregularly few-toothed, 10–40 times as long (vs. E. torreyanum, with leaves usually 3 per node, with blades mostly 5-10 mm wide, serrate to nearly lacerate-toothed, 6-15 times as long as wide).

Synonyms

  • Eupatorium hyssopifolium L. var. laciniatum (Torr. & Gray) Small

Family

Asteraceae

Genus

Eupatorium

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Information from Dichotomous Key of Flora Novae Angliae

11.  Eupatorium torreyanum Short & Peter NC

Torrey’s thoroughwort. Eupatorium hyssopifolium L. var. laciniatum (Torr. & Gray) Small 
• CT. Dry, open areas, such as fields, roadsides, and road cuts.