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• Haloragaceae
• Myriophyllum
• Myriophyllum humile

Myriophyllum humile — low water-milfoil

Facts

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

• 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 (i.e., 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 (i.e., 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

From the dichotomous key of Flora Novae Angliae