Myriophyllum humile (Raf.) Morong

low water-milfoil

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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

Low water-milfoil is morphologically variable depending on water level. It may be confused with the non-native Eurasian water-milfoil.

Habitat

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

Characteristics

Habitat
  • aquatic
  • wetlands
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Flower petal color
blue to purple
Leaf type
  • the leaves are compound (made up of two or more discrete leaflets
  • the leaves are simple (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
  • the edge of the leaf blade is entire (has no teeth or lobes)
Flower symmetry
there are two or more ways to evenly divide the flower (the flower is radially symmetrical)
Number of sepals, petals or tepals
there are no petals, sepals, or tepals in the flower, or they are not clearly present
Fusion of sepals and petals
  • both the petals and sepals are separate and not fused
  • the petals or the sepals are fused into a cup or tube
Stamen number
  • 0
  • 4
Stem nodes swollen
the stem is not swollen at the nodes
Fruit type (general)
the fruit is dry but does not split open when ripe
Fruit length
0.7–1.2 mm
Show All Characteristics
  • Clonal plantlets
    Bulbils
    the plant does not appear to have bulbils
    Bulblets replace flowers
    there are no bulblets where the flowers are located
  • Flowers
    Anther attachment
    the anther is attached by its base to the filament
    Anther opening
    the anthers have narrow slits or furrows that run lengthwise along the anthers
    Anther spurs
    the anthers do not have spurs on them
    Calyx symmetry
    there are two or more ways to evenly divide the calyx (the calyx is radially symmetrical)
    Carpel hairs
    the carpels have no hairs
    Carpels fused
    the carpels are fused to one another
    Cleistogamous flowers
    there are no cleistogamous flowers on the plan
    Corolla morphology
    NA
    Corona lobe length
    0 mm
    Epicalyx
    the flower does not have an epicalyx
    Epicalyx number of parts
    0
    Filament surface
    the filament is smooth, with no hairs or scales
    Flower appearance
    the flowers appear after the leaves have appeared
    Flower description
    the flower has an inferior ovary, with or without a hypanthium
    Flower orientation
    the flower points upwards or is angled outwards
    Flower petal color
    blue to purple
    Flower reproductive parts
    • the flower has both pollen- and seed-producing parts
    • the flower has either only pollen- or only seed-producing parts
    Flower symmetry
    there are two or more ways to evenly divide the flower (the flower is radially symmetrical)
    Flowers sunken into stem
    no
    Form of style
    NA
    Fused stamen clusters
    NA
    Fusion of sepals and petals
    • both the petals and sepals are separate and not fused
    • the petals or the sepals are fused into a cup or tube
    Hairs on flower stalk
    NA
    Hairs on inflorescence
    the axis of the inflorescence has no hairs on it
    Horns in hoods (Asclepias)
    NA
    Hypanthium
    the flower does not have a hypanthium
    Hypanthium length
    0 mm
    Inflorescence one-sided
    the flowers are arrayed in a spiral around the inflorescence axis or branches, or occur singly, or in several ranks
    Inner tepals (Rumex)
    NA
    Interior flower disk
    the flower does not have an interior disc
    Length of flower stalk
    0 mm
    Marks on petals
    there are no noticeable marks on the petals
    Nectar spur
    the flower has no nectar spurs
    Number of branches in umbel
    0
    Number of carpels
    0–4
    Number of pistils
    • 0
    • 1
    Number of sepals, petals or tepals
    there are no petals, sepals, or tepals in the flower, or they are not clearly present
    Number of styles
    0
    Ovary position
    the ovary is below the point of petal and/or sepal attachment
    Perianth shape
    the perianth is another shape
    Petal and sepal arrangement
    • the flower includes neither petals nor sepals
    • the flower includes only one cycle of petals or sepals
    • the flower includes two cycles of petal- or sepal-like structures
    Petal and sepal colors
    blue to purple
    Petal appearance
    the petals are thin and delicate, and pigmented (colored other than green or brown)
    Petal folds or pleats
    the petals of the flower do not have folds or plaits
    Petal glandular dots or scales
    no
    Petal hairs (Viola)
    NA
    Petal length relative to sepals
    the petals are longer than the sepals
    Petal nectaries
    the petals do not have nectaries
    Petal number
    0–4
    Petal tips (Cuscuta)
    NA
    Raceme attachment (Veronica)
    NA
    Reproductive system
    • each flower has only carpels or only stamens, but both types of flower are present on each plant (monoecious)
    • the plant has flowers with both carpels and stamens, as well as flowers with only carpels or only stamens (polygamous)
    Scales inside corolla
    NA
    Sepal and petal color
    • the petals and sepals are similar
    • the sepals are different from the petals
    Sepal appearance
    the sepals are green or brown, and leaf-like in texture
    Sepal appendages
    the sepals do not have appendages on them
    Sepal appendages (Oenothera)
    NA
    Sepal auricles
    the sepals have no auricles
    Sepal color
    green to brown
    Sepal features
    NA
    Sepal number
    0–4
    Sepal uniformity
    all the sepals are about the same size
    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
    Spur number
    NA
    Stamen attachment
    • the stamens are attached at or near the bases of the petals or tepals
    • the stamens are attached at or near the bases of the petals or tepals
    Stamen length
    0.4–1.1 mm
    Stamen lengths differ
    the stamens are all approximately the same length
    Stamen morphology
    the stamens within each cycle are the same
    Stamen number
    • 0
    • 4
    Stamen position relative to petals
    the stamens are lined up with the sepals
    Stamens fused
    the stamens are not attached to one another
    Staminodes
    there are no staminodes on the flower
    Stigma position
    the stigmas are in another position
    Style length
    0 mm
    Style relative length
    NA
    Surface of ovary
    the ovary surface has no points, bumps or wrinkles
    Umbel flower reproductive parts
    NA
    Upper lip of bilabiate corolla
    NA
  • Fruits or seeds
    Achene shape
    NA
    Achene surface (Polygonum)
    NA
    Berry color
    NA
    Capsule color (Viola)
    NA
    Capsule ribs
    NA
    Capsule splitting
    NA
    Carpel beak length
    0 mm
    Fruit (pyxis) dehiscence
    NA
    Fruit beak length
    0 mm
    Fruit features (Brassicaceae)
    NA
    Fruit length
    0.7–1.2 mm
    Fruit length to width ratio
    1
    Fruit locules
    four
    Fruit stalk orientation
    NA
    Fruit type (general)
    the fruit is dry but does not split open when ripe
    Fruit type (specific)
    the fruit is a schizocarp (when dry it splits into sections, each holding one or more seeds)
    Fruit width
    0.7–1.2 mm
    Hair type on fruit
    NA
    Hairs on fruit
    the fruits are not hairy
    Legumes (Fabaceae)
    NA
    Mericarp length
    0.7–1.2 mm
    Mericarp segment shape (Desmodium)
    NA
    Other markings on berry
    NA
    Ovary stipe
    the ovary or fruit does not have a stipe
    Ovary stipe length
    0 mm
    Placenta arrangement
    the plant has apical placentation, where one or a few ovules develop at the top of a simple or compound ovary
    Rows of seeds in fruit (Brassicaceae)
    NA
    Schizocarpic fruit compression
    the fruit is not flattened
    Schizocarpic fruit segments
    4
    Seed length
    0.7–1.2 mm
    Seed number
    4
    Seed surface
    • the seed is hairless
    • the seed is smooth or without clear markings
    Septum in fruit (Brassicaceae)
    NA
    Wings on fruit
    the fruit does not have wings on it
    prickles on fruits
    the fruits do not have thorn-like defensive structures
  • Glands or sap
    Glands on leaf blade
    the leaf blades do not have glandular dots or scales
    Sap
    the sap is clear and watery
    Sap color
    the sap is clear
  • Growth form
    Growth form
    the plant is an herb (it has self-supporting stems)
    Lifespan
    the plant lives more than two years
    Parasitism
    the plant is not parasitic
    Plant color
    the leaves or young stems of the plant are green
    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
    Bracteole number (Apiaceae)
    0
    Bracteole shape
    • the bracteoles are ovate (widest below the middle, and broadly tapering to both ends--egg-shaped)
    • the bracteoles are triangular (the base is on one of the three roughly straight sides)
    Bracteoles
    the plant has bracteoles between the primary bracts and the flowers
    Bracts in plantain (Plantago)
    NA
    Final leaf segment length to width ratio (compound lvs only)
    anything
    Floral bracts
    the flower has one or more bracts associated with it
    Hairs on leaf stalk
    the petiole has no hairs on it
    Hairs on underside of leaf
    the underside of the leaf is not hairy, or it has very few hairs
    Hairs on upper side of leaf
    the upper side of the leaf is not hairy, or it has very few hairs
    Hooked hairs on underside of leaf
    no
    Inflated hairs on leaf
    the leaf blade does not have inflated hairs on it
    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 symmetry
    the leaf blade base is asymmetrical
    Leaf blade bloom
    the underside of the leaf has no noticeable bloom
    Leaf blade edges
    • the edge of the leaf blade has lobes, or it has both teeth and lobes
    • the edge of the leaf blade is entire (has no teeth or lobes)
    Leaf blade flatness
    the leaf is flat (planar) at the edges
    Leaf blade hairs
    NA
    Leaf blade length
    10–25 mm
    Leaf blade primary vein pattern
    the secondary veins branch off at intervals from the primary vein
    Leaf blade shape
    • the leaf blade is linear (very narrow with more or less parallel sides)
    • the leaf blade is oblong (rectangular but with rounded ends)
    • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)
    Leaf blade surface colors
    the upper side of the leaf blade is relatively uniform in color
    Leaf blade texture
    • the leaf blade has a fleshy or spongy texture
    • the leaf blade is herbaceous (has a leafy texture)
    Leaf blade vein pattern
    the major veins of the leaf blade branch, but do not rejoin
    Leaf blade veins
    the leaf blade has one main vein running from the base towards the tip (it may or may not have secondary veins)
    Leaf duration
    the leaves drop off in winter (or they whither but persist on the plant)
    Leaf form
    the leaves are green, with an expanded blade and a leaf-like texture
    Leaf hair orientation
    NA
    Leaf sheath length
    0 mm
    Leaf shiny
    the upper side of the leaf is dull or slightly shiny
    Leaf spines
    there are no spines on the leaf edges
    Leaf stalk
    • the leaves have leaf stalks
    • the leaves have no leaf stalks, but attach directly to the stem
    Leaf stalk attachment to leaf
    the petiole attaches at the basal margin of the leaf blade
    Leaf stalk base
    the petiole base is narrow where it attaches to the stem
    Leaf stalk length
    At least 0 mm
    Leaf teeth and lobes
    • the edge of the leaf blade is entire (has no teeth or lobes)
    • the leaf has a row of two or more lobes on each side of the central axis
    Leaf tip
    • the tip of the leaf blade is acute (sharply pointed)
    • the tip of the leaf blade is obtuse (bluntly pointed)
    Leaf tufts in axils
    there are no clusters of smaller leaves growing out of axils
    Leaf type
    • the leaves are compound (made up of two or more discrete leaflets
    • the leaves are simple (lobed or unlobed but not separated into leaflets)
    Leaf types
    NA
    Leaf variation
    the leaves are nearly similar in size, prominence of teeth, and length of stalks throughout the stem
    Leaflet number
    5–12
    Leaflet petiolules
    the leaflets of the compound leaf lack petiolules
    Leaves per node
    • there are two leaves per node along the stem
    • there is one leaf per node along the stem
    Pinnately compound leaf type
    the pinnately compound leaves have a terminal leaflet (and usually have an odd number of leaflets per axis)
    Specific leaf type
    • the leaf has a row of two or more lobes on each side of the central axis
    • the leaves are simple (lobed or unlobed but not separated into leaflets)
    Stipels
    there are no stipels at the bases of the petiolules
    Stipule edges
    NA
    Stipule features
    NA
    Stipule fused to leaf stalk
    NA
    Stipule length
    0 mm
    Stipule shape
    NA
    Stipules
    there are no stipules on the plant
    Teeth per side of leaf blade
    0
  • Place
    Habitat
    • aquatic
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • in lakes or ponds
    • in rivers or streams
    • shores of rivers or lakes
  • Scent
    Plant odor
    the plant does not have much of a smell
  • Stem, shoot, branch
    Branched tendrils
    NA
    Direction of stem hairs
    NA
    Flowering stem cross-section
    the flowering stem is circular, or with lots of small angles so that it is roughly circular
    Hair between stem nodes
    the stem has no hairs between the nodes
    Hairs between stem nodes
    NA
    Hooked hairs on stem between nodes
    no
    Leaves on stem
    there is at least one full leaf above the base of the flowering stem
    Length of hairs between stem nodes
    0 mm
    Stem bloom
    there is no powdery or waxy film on the stem
    Stem hair distribution
    NA
    Stem nodes swollen
    the stem is not swollen at the nodes
    Stem orientation
    • the stems are upright or angled outwards
    • the stems trail at the base, but may turn upwards at the tips
    Stem roughness between nodes
    the stem does not feel rough
    Stem spacing
    • the plant is growing in tufts, or compact clusters with closely spaced stems, or it is densely matted together in clumps, cushionlike
    • the plant is solitary, or a few plants are growing together
    Tendril origin
    NA
    Tendrils
    the plant does not have tendrils
    Wings on stem
    the stem does not have wings on it

Wetland Status

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

New England Distribution and Conservation Status

Distribution

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

Conservation Status

Exact status definitions can vary from state to state. For details, please check with your state.

Massachusetts
unranked (S-rank: SNR)
Vermont
rare (S-rank: S2)

Native to North America?

Yes

Sometimes Confused With

Myriophyllum farwellii:
leaves typically both alternate and whorled on the same stem, fruits 0.2-2.5 and with 2 rough ridges on the outer surface (vs. M. humile, with leaves all alternate, fruits 0.7-1.2 and without rough projections on the outer suface).

Synonyms

  • Burshia humilis Raf.
  • Myriophyllum ambiguum Nutt. var. natans DC.
  • Myriophyllum capillaceum Torr.
  • Myriophyllum humile forma capillaceum (Torr.) Fern.
  • Myriophyllum humile forma natans (DC.) Fern.

Family

Haloragaceae

Genus

Myriophyllum

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