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• Ambrosia psilostachya

Ambrosia psilostachya — perennial ragweed

Facts

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

• Flowers

  Bases of bract appendages

  NA

  Bract color

  the bracts are not colored or tinged with 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 (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 (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

From the dichotomous key of Flora Novae Angliae