Eupatorium rotundifolium L.

round-leaved 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

Rare in New England, round-leaved thoroughwort occurs on pond shores, clearings and fields in Connecticut and Massachusetts.

Habitat

Forest edges, meadows and fields, shores of rivers or lakes

Characteristics

Habitat
  • terrestrial
  • wetlands
New England state
  • Connecticut
  • Massachusetts
Leaf type
leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
Leaf arrangement
  • 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
15–70 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 oblanceolate (widest near the tip, but otherwise narrow and tapering)
    Bract spines
    the bracts have no spines
    Bract tip shape
    the tips of the bracts acute (have a sharp point)
    Bract width
    0.5–1.5
    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 number
    each flowering stem has four or more flower heads on it
    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
    4.5–6.5 mm
    Inflorescence branching (Solidago)
    NA
    Inflorescence shape
    the inflorescence is flat-topped in profile
    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
    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 details
    the pappus hairs are hooked or barbed
    Seed hair tuft length
    3.5–4.5 mm
    Seed hair tuft tips
    at least some of the pappus hairs are broader at their tips than their bases
    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
    Tuft or plume on fruit
    at least a part of the plume is made up of fine bristles
  • Glands or sap
    Bract resin
    the bracts have resin or resin glands
    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 rhizome (a horizontal underground stem with roots growing from it)
  • 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
    Hairs on upper side of leaf blade
    the upper side of the leaf is fuzzy or hairy
    Leaf arrangement
    • 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
    • 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 hairs
    the leaf blade has simple hairs with no glands, and not tangled or wooly
    Leaf blade length
    15–70 mm
    Leaf blade shape
    • the leaf blade is orbicular (roughly circular, as wide as long)
    • 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 obtuse (bluntly pointed)
    • the tip of the leaf blade is rounded, with no point
    Leaf blade veins
    the leaf blade has three main veins running from the base towards the tip
    Leaf blade width
    15–60 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 no leaf stalks, but attach directly to the stem
    Leaf stalk length
    At least 0 mm
    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
    Teeth per side of leaf blade
    8–25
  • Place
    Habitat
    • terrestrial
    • wetlands
    New England state
    • Connecticut
    • Massachusetts
    Specific habitat
    • edges of forests
    • meadows or fields
    • shores of rivers or lakes
  • 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 point mostly upwards to outwards
    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

Occurs in wetlands or non-wetlands. (Wetland indicator code: FAC)

New England Distribution and Conservation Status

Distribution

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

Conservation Status

Exact status definitions can vary from state to state. For details, please check with your state.

Connecticut
unrankable (S-rank: SU)
Maine
historical (S-rank: SH)
Massachusetts
unranked (S-rank: SNR)

var. ovatum

Massachusetts
unranked (S-rank: SNR)

var. rotundifolium

Connecticut
unrankable (S-rank: SU)
Massachusetts
unranked (S-rank: SNR)

Native to North America?

Yes

Sometimes Confused With

Eupatorium pubescens:
leaf blades oblong-ovate to ovate, mostly 1.5–2 times as long as wide, obtuse to acute at apex, usually with serrate margins (vs. E. rotundifolium, with leaf blades triangular-ovate to suborbicular, mostly 1–1.5 times as long as wide, rounded to obtuse at the apex, usually with crenate margins).

Family

Asteraceae

Genus

Eupatorium

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Information from Dichotomous Key of Flora Novae Angliae

8.  Eupatorium rotundifolium L. NC

round-leaved thoroughwort. CT, MA; also reported from RI by Kartesz (1999), but specimens 
are unknown. Pond shores, clearings, fields.