Myriophyllum tenellum Bigelow

slender 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

Slender water-milfoil gets its common name from its slender, leafless stems, which differ from other milfoils whose stems are leafy. The flowers are wind pollinated, and the carpellate (seed-bearing) flowers mature before the staminate (pollen-bearing) flowers, thereby reducing the chance of self pollination.

Habitat

Lacustrine (in lakes or ponds), 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
  • pink to red
Leaf type
  • NA
  • the leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
Leaf arrangement
  • NA
  • alternate: there is one leaf per node along the stem
Leaf blade edges
  • NA
  • 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 four petals, sepals, or tepals in the flower
Fusion of sepals and petals
both the petals and sepals are separate and not fused
Stamen number
  • 0
  • 4
Fruit type (general)
the fruit is dry but does not split open when ripe
Fruit length
1–1.2 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 color
    the anthers show no hint of a pink, reddish or purplish tint
    Anther length
    1.2–1.7 mm
    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 growth after flowering
    • NA
    • the calyx grows to cover or partially cover the fruit
    Calyx symmetry
    there are two or more ways to evenly divide the calyx (the calyx is radially symmetrical)
    Carpels fused
    the carpels are fused to one another
    Cleistogamous flowers
    there are no cleistogamous flowers on the plan
    Corolla morphology
    NA
    Corolla palate
    no
    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
    • pink to red
    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
    Fringed petal edges
    the petals are not fringed
    Fused stamen clusters
    NA
    Fusion of sepals and petals
    both the petals and sepals are separate and not fused
    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 length
    20–50 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
    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 four petals, sepals, or tepals in the flower
    Number of styles
    0
    Ovary position
    the ovary is below the point of petal and/or sepal attachment
    Petal and sepal arrangement
    the flower includes two cycles of petal- or sepal-like structures
    Petal and sepal colors
    • blue to purple
    • pink to red
    Petal appearance
    the petals are thin and delicate, and pigmented (colored other than green or brown)
    Petal base
    the petal narrows gradually or does not narrow at the base
    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 number
    4
    Petal shape
    • the petal outline is elliptic (shaped like an ellipse; widest near the middle and tapering at both ends)
    • the petal outline is oblong (rectangular, but with rounded ends)
    • the petal outline is obovate (roughly egg-shaped, but with the widest point above the middle of the leaf blade)
    Petal tip shape
    the petal tip is rounded
    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 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 number
    4
    Sepal uniformity
    all the sepals are about the same size
    Spur length
    0 mm
    Spur number
    NA
    Stamen appendages
    stamen appendages are absent
    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 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 relative length
    anything
    Stamens fused
    the stamens are not attached to one another
    Staminodes
    there are no staminodes on the flower
    Stigma length
    At least 0 mm
    Stigma position
    • NA
    • 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
    Fruit (pyxis) dehiscence
    NA
    Fruit beak length
    0 mm
    Fruit features (Brassicaceae)
    NA
    Fruit length
    1–1.2 mm
    Fruit length relative to sepals
    • NA
    • the fruit is about the same length as its associated sepals
    • the fruit is shorter than its associated sepals
    Fruit locules
    four
    Fruit shape
    the fruit is another shape than those described
    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)
    Hair type on fruit
    NA
    Hairs on fruit
    the fruits are not hairy
    Legumes (Fabaceae)
    NA
    Mericarp length
    1–1.2 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 number
    4
    Seeds comose
    no hairs
    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
    • NA
    • 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)
    Horizontal rooting stem
    the plant does not have stolons
    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
    Plants darken when dry
    no
    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 edges
    the bracteole margins are entire (without teeth, lobes or hairs)
    Bracteole number (Apiaceae)
    0
    Bracteole shape
    • the bracteoles are linear (very narrow, with more or less parallel sides)
    • 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
    • there are no bracteoles on the plant
    Bracts in plantain (Plantago)
    NA
    Final leaf segment length (compound lvs only)
    0 mm
    Final leaf segment length to width ratio (compound lvs only)
    0
    Final leaf segment width (compound lvs only)
    0 mm
    Floral bract texture
    the floral bracts are green, with a leaf-like texture
    Floral bracts
    the flower has one or more bracts associated with it
    Flower bract length
    1–4 mm
    Hairs on leaf stalk
    NA
    Hairs on underside of leaf
    • NA
    • the underside of the leaf is not hairy, or it has very few hairs
    Hairs on upper side of leaf
    • NA
    • the upper side of the leaf is not hairy, or it has very few hairs
    Hooked hairs on underside of leaf
    NA
    Inflated hairs on leaf
    • NA
    • the leaf blade does not have inflated hairs on it
    Leaf arrangement
    • NA
    • alternate: there is one leaf per node along the stem
    Leaf blade base
    • NA
    • the leaf has no stalk
    Leaf blade bloom
    • NA
    • the underside of the leaf has no noticeable bloom
    Leaf blade edges
    • NA
    • the edge of the leaf blade is entire (has no teeth or lobes)
    Leaf blade hairs
    NA
    Leaf blade length
    At least 0 mm
    Leaf blade surface colors
    • NA
    • the upper side of the leaf blade is relatively uniform in color
    Leaf blade texture
    the leaf blade is herbaceous (has a leafy texture)
    Leaf blade width
    At least 0 mm
    Leaf duration
    • NA
    • the leaves drop off in winter (or they whither but persist on the plant)
    Leaf form
    the leaves are small and thin and lack leaf stalks
    Leaf hair orientation
    NA
    Leaf sheath length
    0 mm
    Leaf spines
    there are no spines on the leaf edges
    Leaf stalk
    the leaves have no leaf stalks, but attach directly to the stem
    Leaf stalk attachment to leaf
    NA
    Leaf stalk base
    NA
    Leaf stalk length
    0 mm
    Leaf teeth and lobes
    • NA
    • the edge of the leaf blade is entire (has no teeth or lobes)
    Leaf tufts in axils
    there are no clusters of smaller leaves growing out of axils
    Leaf type
    • NA
    • the leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
    Leaf types
    • NA
    • There is a gradual change in appearance of the leaves from the base (or near the base) of the plant to those from further up on the stem, with leaves progressively changing as one moves higher on the stem (often becoming shorter, or less toothed/lobed, and/or with shorter petioles).
    Leaf variation
    • NA
    • the leaves are nearly similar in size, prominence of teeth, and length of stalks throughout the stem
    Leaflet number
    0
    Leaflet petiolules
    NA
    Leaves per node
    • NA
    • there is one leaf per node along the stem
    Pinnately compound leaf type
    NA
    Specific leaf type
    • NA
    • the leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
    Stipels
    NA
    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
    • 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
    • the flowering stem has no leaves above the base
    • there is at least one full leaf above the base of the flowering stem
    Length of hairs between stem nodes
    0 mm
    Plant height
    25–550 cm
    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 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.

Connecticut
fairly widespread (S-rank: S4)
Massachusetts
unranked (S-rank: SNR)

Native to North America?

Yes

Family

Haloragaceae

Genus

Myriophyllum

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Information from Dichotomous Key of Flora Novae Angliae

9.  Myriophyllum tenellum Bigelow N

slender water-milfoil. CT, MA, ME, NH, RI, VT. Shallow, acidic to circumneutral water of lakes, pond shores.