Iva annua L.

rough marsh-elder

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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

Not reaching farther north than Pennsylvania in its native range, rough marsh-elder is non-native in New England, but a common annual elsewhere in North America. Like ragweed, it is a source of allergenic airborne pollen. Rough marsh-elder was apparently cultivated by prehistoric Native Americans (Scioto Hopewell) as a seed crop, based on archeological remains documenting increases in achene size by 2000 BC.

Habitat

Anthropogenic (man-made or disturbed habitats)

Characteristics

Habitat
terrestrial
New England state
  • Maine
  • Massachusetts
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 teeth
Flower type in flower heads
the flower head has tubular disk flowers in the center and ray flowers, these often strap-shaped, around the periphery
Ray flower color
NA
Tuft or plume on fruit
NA
Spines on plant
the plant has no spines
Leaf blade length
30–150 mm
Show All Characteristics
  • Flowers
    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 margins
    there are fine hairs along the bract margins
    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 separation
    the bracts appear completely unconnected to one another on all flower heads
    Bract spines
    the bracts have no spines
    Bract texture
    the bracts have a similar texture to a leaf
    Bracts
    the bracts in separate cycles are similar or gradually changing from the outer to inner cycles
    Disk flower color
    white
    Disk flower lobe number
    5
    Disk flower proportions
    NA
    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
    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 papery scales on it
    Flower head profile
    • the disk is flat or nearly flat across the top
    • the disk is rounded across the top
    Flower head shape
    the flower head is hemispherical (like the bottom half of a sphere)
    Flower type in flower heads
    the flower head has tubular disk flowers in the center and ray flowers, these often strap-shaped, around the periphery
    Height of flower head base
    1.5–4 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
    Number of bracts at flower head base
    3–15
    Ovary cross-section
    the ovary is compressed (flattened)
    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
    Peduncle length
    0–1 mm
    Ray flower color
    NA
    Ray flower reproductive parts
    NA
    Ray flowers
    NA
    Reproductive system
    all the flowers on the plant contain both carpels and stamens
    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
    there are no obvious branches on the style
    Style branches
    the style branch is narrow at the tip, or the style branches are narrow at the tips
    Width of flower head base
    3–5 mm
  • Fruits or seeds
    Number of pappus parts
    NA
    Ovary length in developed fruit
    2–3 mm
    Seed hair tuft bases
    NA
    Seed hair tuft color
    NA
    Seed hair tuft details
    NA
    Seed hair tuft tips
    NA
    Seed hairs uniform
    NA
    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
    Ovary glands
    there are glands on the ovary surface
  • 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
  • Leaves
    Hairs on underside of leaf blade
    the underside 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)
    Leaf blade edges
    the edge of the leaf blade has teeth
    Leaf blade flatness
    the leaf is flat (planar) at the edges
    Leaf blade hairs
    the leaf blade has simple hairs with no glands, and not tangled or wooly
    Leaf blade length
    30–150 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 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 tip
    • the tip of the leaf blade is acuminate (tapers to a long, thin point)
    • 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
    8–80 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 length
    5–30 mm
    Leaf type
    leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
    Specific leaf type
    the leaves are simple (i.e., lobed or unlobed but not separated into leaflets
  • Place
    Habitat
    terrestrial
    New England state
    • Maine
    • Massachusetts
    Specific habitat
    man-made or disturbed habitats
  • Stem, shoot, branch
    Leaves on stem
    there is at least one full leaf above the base of the flowering stem
    Stem internode hair direction
    • NA
    • the hairs are pressed flat against the plant, pointing either towards the plant's tip or towards it's base
    • 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
absent
Maine
present
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
unranked (S-rank: SNR)

var. annua

Massachusetts
unranked (S-rank: SNR)

Native to North America?

Yes and no (some introduced)

Sometimes Confused With

Iva frutescens:
leaf blades and axis of capitulescence glabrous, petioles 3–10 mm long, and peduncles 1–3 mm long (vs. I. annua, with leaf blades adaxially strigose-scaberulous, axis of capitulescence pubescent, petioles mostly 5-20 mm long, and peduncles 0-1 mm long).

Synonyms

  • Iva ciliata Willd.

Family

Asteraceae

Genus

Iva

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Information from Dichotomous Key of Flora Novae Angliae

1.  Iva annua L. E

rough marsh-elder. Iva ciliata Willd. • MA, ME. Roadsides, dumps, waste areas.