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• Ambrosia bidentata

Ambrosia bidentata — lance-leaved ragweed

Facts

Lance-leaved ragweed is an annual that is native to the North America but introduced in New England, where it occurs only in Connecticut. In other parts of the United States it contributes to airborne allergens, as do the other ragweeds (Ambrosia).

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 pink, red or purple

  Bract cycle number

  there is one main cycle of bracts

  Bract outer side hair type

  the bracts are hairy on their outer surfaces, with hairs having glands (a swelling at the tip of the hair)

  Bract outer side hairs

  the bracts are hairy on their outer surfaces

  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 extension appearance

  NA

  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
  • 6-10

  Disk flower reproductive parts

  the disk flower has either only pollen- or only seed-producing parts

  Disk width

  1.5–2.5 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

  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

  Flower head shape

  the flower head is cup-shaped (the sides diverge, then curve upwards and become parallel)

  Flower head width

  1.5–2.5 mm

  Flower type in flower heads

  the flower head has disk flowers only, and lacks the strap-shaped flowers

  Height of flower head base

  1.5–8 mm

  Inflorescence branching (Solidago)

  NA

  Inflorescence shape

  the inflorescence is not flat-topped but appears rounded, with some flower heads distinctly higher than others

  Inflorescence stem

  hairs are present on the stem of the inflorescence

  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 hairs on it, but the hairs have no glands

  Ovary hairs

  the ovary has 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)

  Peduncle length

  At least 0 mm

  Ray flower color

  NA

  Ray flower reproductive parts

  the ray flowers have carpels or stamens, but not both

  Ray flowers

  0

  Ray length

  0 mm

  Reproductive system

  the flowers on the plant may have either carpels or stamens, but always in separate flowers

  Scale tip

  NA

  Smaller bracts at base of bracts

  there is no smaller, outer cycle of bracts

  Style branch number

  the style has one branch

  Width of flower head base

  2.5–3.5 mm

• Fruits or seeds

  Number of pappus parts

  0

  Ovary length in developed fruit

  4–5 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

  there is a thickened taproot on the plant

• 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

  • 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

  Leaf blade base shape

  • the base of the leaf blade is rounded
  • the base of the leaf blade is truncate (ends abruptly in a more or less straight line as though cut off)
  • the base of the leaf is cordate (heart-shaped) or sagittate (arrow-shaped)

  Leaf blade edges

  • the edge of the leaf blade has no teeth or lobes
  • 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

  150–400 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 tip

  the tip of the leaf blade is acuminate (tapers to a long, thin point)

  Leaf blade veins

  the leaf blade has one main vein running from the base towards the tip

  Leaf blade width

  4–10 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

  0–0.5 mm

  Leaf tip extension

  NA

  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

  1–2

• Place

  Habitat

  terrestrial

  New England state

  Connecticut

  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 length

  At least 0 mm

  Stem internode hair type

  • at least some of the hairs on the stem are branched
  • 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

Not classified

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae