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Myriophyllum spicatum — Eurasian water-milfoil

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Facts

The invasive Eurasian water-milfoil was first found in Lake Minnetonka, Minnesota in 1987. It can thrive in a wide range of conditions, and it outcompetes native plants and animals. It spreads rapidly, propagating from seeds, roots, and stem fragments, the latter developing roots even before they are separated from the parent plant.

Habitat

Lacustrine (in lakes or ponds), riverine (in rivers or streams)

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
aquatic
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Vermont
Leaf position
the leaves are all submerged underwater
Leaf arrangement
whorled: there are three or more leaves per node along the stem
Leaf blade length
30–35 mm
Petal or sepal number
  • there are four petals, sepals, or tepals in the flower
  • there are no petals, sepals, or tepals in the flower, or they are not clearly present
Petal color
pink
Specific leaf type
  • the leaf has three or more lobes distributed along a central axis
  • the leaf is once pinnately divided and the segments are very narrow, each side providing the appearance of a comb
  • the leaf is pinnately compound (i.e., it has three or leaflets distributed along a central axis
Floating leaf shape
NA
Underwater leaf blade width
10–25 mm
Fruit type (general)
the fruit is dry and splits open when ripe
Underwater leaf length
30–35 mm
Show all characteristics

  • Clonal plantlets

    Turion length
    0 mm

  • Flowers

    Anther color
    there is a noticeable pink, reddish or purplish tint to the anthers
    Carpels fused
    the carpels are fused to one another
    Flower lower lip length
    0 mm
    Flower position
    the flowers are above the surface of the water
    Flower symmetry
    there are two or more ways to evenly divide the flower (the flower is radially symmetrical)
    Inflorescence length
    60–100 mm
    Inflorescence type
    the inflorescence is a spike (a long unbranched stem with flowers along it that lack stalks)
    Length of flower stalk
    0 mm
    Nectar spur
    the flower has no nectar spurs
    Number of carpels
    0–4
    Ovary position
    the sepals and/or petals are attached above the ovary
    Palate on corolla
    no
    Petal and sepal arrangement
    the flower includes two cycles of petal- or sepal-like structures
    Petal appearance
    the petals are thin and delicate, and pigmented (colored other than green or brown)
    Petal color
    pink
    Petal length
    1.5–2.5 mm
    Petal number
    0–5
    Petal or sepal number
    • there are four petals, sepals, or tepals in the flower
    • there are no petals, sepals, or tepals in the flower, or they are not clearly present
    Pistil number
    • 0
    • 1
    Sepal appearance
    the sepals resemble leaves in color and texture
    Sepal length
    0.5–1 mm
    Sepal number
    0–4
    Sepals fused only to sepals
    the sepals are fused to each other (not other flower parts), at least near their bases
    Spur length
    0 mm
    Stamen length
    1.2–2 mm
    Stamen number
    • 0
    • 8
    Stamen position relative to petals
    NA
    Stamens fused
    the stamens are not fused to one another
    Stamens fused to petals
    the stamens are not fused to the petals or tepals
    Style length
    0 mm
    Style number
    0

  • Fruits or seeds

    Fruit beak length
    0 mm
    Fruit length
    2–3 mm
    Fruit type (general)
    the fruit is dry and splits open when ripe
    Fruit type (specific)
    the fruit is a schizocarp (when dry it splits into sections, each holding one or more seeds)

  • Glands or sap

    Oil glands on nodes
    none of the nodes have oil glands
    Sap
    the sap is clear and watery

  • Growth form

    Lifespan
    the plant lives more than two years
    Root septa
    the roots do not have transverse septa
    Roots floating in water
    there are no clusters of roots floating in the water
    Turions
    there are no turions on the plant
    Underground organs
    the plant has a rhizome (a horizontal underground stem with roots growing from it)

  • Leaves

    Bract position (Sparganium)
    NA
    Bract relative length
    At least 1379 mm
    Bracts
    the flowers or their pedicels have bracts at their bases
    Floating leaf basal lobes
    NA
    Floating leaf blade width
    0 mm
    Floating leaf length
    0 mm
    Floating leaf shape
    NA
    Floating leaf tip
    NA
    Floral bract form
    the bracts are much more lobed, or much less lobed, than the foliage leaves
    Floral bract length
    Up to 20 mm
    Leaf arrangement
    whorled: there are three or more leaves per node along the stem
    Leaf blade length
    30–35 mm
    Leaf blade veins
    the lateral veins radiate from the base and continue to spread away from the centerline of the leaf, or branch off the central vein at intervals
    Leaf blade width
    10–25 mm
    Leaf position
    the leaves are all submerged underwater
    Leaf special features
    none of the mentioned special features are present
    Leaf-like branch segments
    12–20
    Leaf-like branch shape
    NA
    Specific leaf type
    • the leaf has three or more lobes distributed along a central axis
    • the leaf is once pinnately divided and the segments are very narrow, each side providing the appearance of a comb
    • the leaf is pinnately compound (i.e., it has three or leaflets distributed along a central axis
    Staminate bract edge (Myriophyllum)
    the edges of the staminate bracts are either smooth and without teeth, or with tiny, outward-pointing teeth
    Stipule appearance
    NA
    Stipule fused to leaf
    NA
    Stipules
    there are no stipules on the plant
    Stipules fused around stem
    NA
    Trap-bladder length
    0 mm
    Underwater leaf air passage number
    At least 1439
    Underwater leaf air passage relative width
    At least 4336
    Underwater leaf air passage row number
    0
    Underwater leaf blade edges
    the underwater leaf has smooth edges, without teeth
    Underwater leaf blade shape
    • the underwater leaf blade is oblong (rectangular but with rounded ends)
    • the underwater leaf blade is obovate (egg-shaped, but with the widest point above the middle of the underwater leaf blade)
    Underwater leaf blade width
    10–25 mm
    Underwater leaf length
    30–35 mm
    Underwater leaf stalk
    • no
    • yes
    Underwater leaf stalk length
    0–2 mm
    Underwater leaf tip shape
    • the tip of the underwater leaf is rounded, with no point
    • the tip of the underwater leaf is truncate (ends abruptly in a more or less straight line as though cut off)
    Veins in floating leaf
    0

  • Place

    Habitat
    aquatic
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Vermont
    Specific habitat
    • in lakes or ponds
    • in rivers or streams

  • Stem, shoot, branch

    Flowering stem growth form
    the flowering stem is upright

Wetland status

Occurs only in wetlands. (Wetland indicator code: OBL)

In New England

Distribution

Connecticut
present, invasive, prohibited
Maine
present, invasive, prohibited
Massachusetts
present, invasive, prohibited
New Hampshire
present, invasive, prohibited
Rhode Island
absent
Vermont
present, invasive, prohibited

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

8.  Myriophyllum spicatum L. E

Eurasian water-milfoil. CT, MA, ME, NH, VT. Slow or still-moving, circumneutral to basic water of lakes and rivers.

Native to North America?

No

Sometimes confused with

Myriophyllum verticillatum:
lower bracts of inflorescence 2 or more times as long as the flowers or fruits, prominently toothed to lobed, upper bracts of inflorescence toothed to lobed (vs. M. spicatum, with lower bracts of inflorescence less than 2 times as long as the flowers or fruits, upper bracts of inflorescence entire to minutely toothed).
Myriophyllum sibiricum:
middle leaves with mostly 6–12 segments on each side of the rachis, upper leaves rounded at the apex, stems of +/- similar diameter below the inflorescence and near the stem base, and turions formed in the fall (vs. M. spicatum, with the middle leaves with mostly 12–20 segments on each side of the rachis, uppermost leaves truncate at the apex, stems thicker below the inflorescence than at the stem base, up to twice as thick, and turions not formed).

Family

Haloragaceae

Genus

Myriophyllum