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Eupatorium altissimum — tall thoroughwort

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Facts

Tall thoroughwort is a native of dry soils and open areas, especially on limestone. The northern limit of its natural distribution is in Connecticut and Massachusetts

Habitat

Anthropogenic (man-made or disturbed habitats), forest edges

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
terrestrial
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
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
15–120 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 hairs
    the bracts are hairy on their outer surfaces
    Bract separation
    the bracts appear completely unconnected to one another on all flower heads
    Bract shape
    the main bracts are oblong (roughly rectangular but rounded at the ends)
    Bract spines
    the bracts have no spines
    Bract texture
    the bracts have a similar texture to a leaf
    Bract tip color
    the tips are a different color from the center of the bract
    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 obtuse (have a blunt point)
    • the tips of the bracts are rounded
    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 position
    some or all the flower heads are grouped in clusters of two or more
    Flower head profile
    • the disk is flat or nearly flat across the top
    • the disk is rounded across the top
    Flower head shape
    • NA
    • 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
    Peduncle orientation
    the flower heads are held upright, or slightly angled outwards
    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 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
    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)
    • 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
    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 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
    15–120 mm
    Leaf blade shape
    • the leaf blade is elliptic (widest near the middle and tapering at both ends)
    • the leaf blade is lanceolate (lance-shaped; widest below the middle and tapering at both ends)
    • the leaf blade is oblong (rectangular but with rounded ends)
    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 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
    8–30 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
    • there are no clusters of smaller leaves
    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
    • Massachusetts
    Specific habitat
    • edges of forests
    • man-made or disturbed habitats

  • Scent

    Plant odor
    the plant does not have much of an odor

  • 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
    • 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

Not classified

In New England

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.

Massachusetts
not applicable (S-rank: SNA)

From Flora Novae Angliae dichotomous key

2.  Eupatorium altissimum L. E

tall thoroughwort. Eupatorium saltuense Fern. • CT, MA. Railroads, roadsides, clearings.

Native to North America?

Yes and no (some introduced)

Sometimes confused with

Eupatorium serotinum:
capitula with 9-15 disk flowers and principal leaves with petioles 10-25 mm long (vs. E. altissimum, with capitula with 5 disk flowers and leaves sessile or subsessile).
Eupatorium sessilifolium:
leaf blades lanceolate to oblong, usually widest below the middle, truncate to rounded at the base (vs. E. altissimum, with leaf blades narrow-elliptic to oblanceolate, usually widest at or above the middle, cuneate at the base).

Synonyms

  • Eupatorium saltuense Fern.

Family

Asteraceae

Genus

Eupatorium