Ambrosia psilostachya DC.

perennial ragweed

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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

Perennial ragweed is one of the species whose pollen contributes most to airborne allergens, after common ragweed (Ambrosia artemisiifolia). Perennial ragweed can be distinguished from common ragweed by the leaf shape: simply pinnately lobed in perennial ragweed, doubly pinnately lobed in common ragweed.

Habitat

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

Characteristics

Habitat
terrestrial
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Vermont
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
Leaf blade edges
the edge of the leaf blade has lobes, or it has both teeth and lobes
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
NA
Spines on plant
the plant has no spines
Leaf blade length
20–140 mm
Flower head width
2–5 mm
Disk flower number
  • 1-5
  • 11-20
  • 21-50
  • 6-10
Show All Characteristics
  • Flowers
    Bases of bract appendages
    NA
    Bract color
    the bracts are not colored or tinged with pink, red or purple
    Bract cycle number
    there is one main cycle of bracts
    Bract outer side hair type
    the bracts are hairy, with simple hairs on their outer surface
    Bract separation
    at least some flower heads have bracts connected to one another at or near their bases
    Bract spines
    the bracts are prickly on the outer side
    Bract texture
    the bracts appear leathery or hardened
    Bract tip color
    the tips are a different color from the center of the bract
    Bract tip extension edge
    there are projections from the bract tips
    Bracts
    there are at least two distinct forms of bracts in different cycles
    Disk flower color
    green to brown
    Disk flower lobe number
    5
    Disk flower number
    • 1-5
    • 11-20
    • 21-50
    • 6-10
    Disk flower reproductive parts
    the disk flower has either only pollen- or only seed-producing parts
    Disk flower shape
    the disk flower is tube-shaped (cylindrical), or gradually widening like a funnel
    Disk width
    2–4 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, 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 papery scales on it
    Flower head platform surface
    the scales are slightly hairy, at least near the top
    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
    Flower head shape
    the flower head is cup-shaped (the sides diverge, then curve upwards and become parallel)
    Flower head width
    2–5 mm
    Flower type in flower heads
    the flower head has disk flowers only, and lacks the strap-shaped flowers
    Height of flower head base
    3–5 mm
    Inflorescence branching (Solidago)
    NA
    Inflorescence shape
    • the flower heads grow in clusters from the axils of the branches or leaves
    • the inflorescence is not flat-topped but appears rounded, with some flower heads distinctly higher than others
    Inflorescence stem
    the stem of the inflorescence is not hairy
    Ovary beak
    there is a beak on the ovary
    Ovary cross-section
    the ovary is roughly square or with four corners
    Ovary hair type
    the ovary has no hairs on it
    Ovary hairs
    the ovary has no hairs on it
    Ovary profile
    • in profile, the ovary is roughly egg-shaped, but widest above the middle
    • in profile, the ovary is roughly elliptical (widest in the middle, tapering to both ends)
    Ovary surface
    the ovary surface is textured with tiny points, bumps or wrinkles
    Peduncle length
    2–4 mm
    Ray flower color
    NA
    Ray flower reproductive parts
    NA
    Ray flowers
    0
    Ray length
    0 mm
    Reproductive system
    all the flowers on some plants have carpels, while all the flowers on other plants have 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 one branch
    Width of flower head base
    3–5 mm
  • Fruits or seeds
    Number of pappus parts
    0
    Ovary beak length
    0.7–1 mm
    Ovary length in developed fruit
    2–3 mm
    Ovary width in developed fruit
    2–3 mm
    Seed hair tuft bases
    NA
    Seed hair tuft color
    NA
    Seed hair tuft details
    NA
    Seed hair tuft length
    0 mm
    Seed hair tuft tips
    NA
    Seed hairs uniform
    NA
    Seed tuft scale number
    0
    Seed tuft type
    there is no pappus on the ovary
    Top of disk flower ovary
    NA
    Tuft or plume on fruit
    NA
  • Glands or sap
    Leaf blade glands
    the leaf blades have glandular (translucent) dots or scales
    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 annual, it lacks evidence of previous years' growth
    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
    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
    • 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
    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
    • the base of the leaf blade is truncate (ends abruptly in a more or less straight line as though cut off)
    Leaf blade edges
    the edge of the leaf blade has lobes, or it has both teeth and lobes
    Leaf blade hairs
    the leaf blade has simple hairs with no glands, and not tangled or wooly
    Leaf blade length
    20–140 mm
    Leaf blade shape
    • the leaf blade is oblanceolate (lance-shaped, but with the widest point above the middle of the leaf blade)
    • the leaf blade is triangular, with the stalk or attachment point on one of the sides
    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
    8–50 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 leaf stalks
    Leaf stalk length
    0–30 mm
    Leaf tip extension
    NA
    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
    • the leaf has a row of two or more lobes on each side of the central axis, and each lobe itself has rows of lobes on each side of the lobe's central axis
    • the leaves are simple (i.e., lobed or unlobed but not separated into leaflets
  • Place
    Habitat
    terrestrial
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Vermont
    Specific habitat
    • man-made or disturbed habitats
    • meadows or fields
  • Stem, shoot, branch
    Leaves on stem
    there is at least one full leaf above the base of the flowering 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
    • 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

Wetland Status

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

New England Distribution and Conservation Status

Distribution

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

Conservation Status

None

Native to North America?

No

Sometimes Confused With

Ambrosia artemisiifolia:
leaf blades commonly twice pinnately lobed, plants annual, and carepellate involucres with 4-7 sharp spines near or above the middle (vs. A. psilostachya, with leaf blades usually once pinnately lobed, plants perennial, and carpellate involucres with 4 tubercles near apex).

Synonyms

  • Ambrosia coronopifolia Torr. & Gray
  • Ambrosia psilostachya DC. var. coronopifolia (Torr. & Gray) Farw.

Family

Asteraceae

Genus

Ambrosia

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Information from Dichotomous Key of Flora Novae Angliae

3.  Ambrosia psilostachya DC. E

perennial ragweed. Ambrosia coronopifolia Torr. & Gray; A. psilostachya DC. var. coronopifolia (Torr. & Gray) Farw. • CT, MA, ME, NH, VT. Roadsides, fields, railroads, disturbed soil.