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• Helanthium tenellum

Helanthium tenellum — dwarf burhead

Facts

Dwarf burhead is a globally rare aquatic annual, with a range that includes parts of North, Central and South America. It has been found in New England in Connecticut and Massachusetts. Conservation plans include attempted reintroductions to sites where it was formerly present.

Habitat

Shores of rivers or lakes, wetland margins (edges of wetlands)

Characteristics

• Clonal plantlets

  Axillary bulblets

  there are no bulblets being produced in axils

• 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

  0.2 mm

  Bulblets replace flowers

  there are no bulblets where the flowers are located

  Carpels fused

  the carpel is solitary or (if 2 or more) the carpels are not fused to one another

  Filament surface

  the filament surface has no hairs or scales on it

  Flower bract length

  2.8–4.9 mm

  Flower bracts

  there are bracts associated with the flower

  Flower number

  4–12

  Flower orientation

  the flowers curve or droop downwards

  Flower petal color

  • pink to red
  • white

  Flower petal length

  1–3 mm

  Flower shape

  the flower is flattened or platter-shaped

  Flower symmetry

  there are two or more ways to evenly divide the flower (the flower is radially symmetrical)

  Form of style

  the flower has two or more completely separate styles

  Fringed petal edges

  the petals are not fringed

  Hairs on flower stalk

  the flower stalk has no hairs on it

  Inflorescence hair glands

  the axis of the inflorescence has no hairs on it

  Inflorescence length

  60 mm

  Inflorescence type

  the inflorescence is an umbel (with an axis so short it appears the flowers all originate from the same point)

  Inflorescence width

  80 mm

  Length of flower stalk

  5–30 mm

  Length of peduncle

  12–40 mm

  Marks on petals

  there are no noticeable marks on the petals

  Nectar spur

  the flower has no nectar spurs

  Number of carpels

  15–20

  Number of pistils

  6 or more

  Number of sepals and/or petals

  there are three petals, sepals or tepals in the flower

  Number of styles

  1

  Ovary position

  the ovary is above the point of petal and/or sepal attachment

  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 base

  the petal narrows abruptly at the base

  Petal fusion

  the perianth parts are separate

  Petal hairs on inner/upper surface

  there are no hairs on the inner/upper petal surface

  Petal nectaries

  the petals do not have nectaries

  Sepal appearance

  the sepals resemble leaves in color and texture

  Sepal length

  1–2 mm

  Sepal orientation

  • the sepals are pressed against the plant, or jutting stiffly upward
  • the sepals are slightly curved outwards from the plant

  Sepals fused only to sepals

  the sepals are separate from one another

  Spathe

  the plant does not have a spathe

  Spathe form

  NA

  Spathe length

  0 mm

  Stamen number

  9

  Stamen position relative to petals

  NA

  Stamen types

  the stamens within a cycle are all similar

  Stamens fused

  the stamens are not fused to one another

  Stamens fused outwards

  the stamens are not fused to the petals or tepals

  Style petal-like

  the style is not broad and flattened like a petal

  Tepals

  the petals and sepals are different in size and color

• Fruits or seeds

  Berry color

  NA

  Capsule ridges

  NA

  Fruit beak length

  0.1–0.2 mm

  Fruit compartments

  there is only one locule in the fruit

  Fruit cross-section

  the fruit is at least somewhat flattened

  Fruit length

  0.8–1.5 mm

  Fruit stalk orientation

  the fruits curve or droop downwards

  Fruit type (general)

  the fruit is dry but does not split open when ripe

  Fruit type (specific)

  the fruit is an achene (dry, usually 1-seeded, does not separate or split open at maturity)

  Fruit width

  0.8–1 mm

  Other markings on berry

  NA

• Glands or sap

  Sap

  the sap is milky and opaque, and may be white or colored

• Growth form

  Lifespan

  the plant lives only a single year or less

  Root septa

  the roots do not have transverse septa

  Underground organs

  there are only slender roots on the plant

• Leaves

  Hairs on underside of leaf blade

  the underside of the leaf is not hairy, or has very few hairs

  Hairs on upper side of leaf blade

  the upper side of the leaf is not hairy, or has very few hairs

  Leaf arrangement

  the leaves are growing only at the base of the plant (basal)

  Leaf blade basal lobes

  the leaf blades do not have basal lobes

  Leaf blade base

  • the leaf has a distinct leaf stalk (petiole)
  • the leaf has no stalk

  Leaf blade base shape

  the base of the leaf blade is cuneate (wedge-shaped, tapers to the base with relatively straight, converging edges), or narrow

  Leaf blade bloom

  the underside of the leaf blade has no noticeable waxy or powdery bloom

  Leaf blade cross-section

  the leaf blade is more or less flat in cross-section

  Leaf blade faces

  both surfaces of the leaf blade are exposed

  Leaf blade form

  Fully-formed (i.e., expanded), +/- green leaf blades are found somewhere on the plant

  Leaf blade length

  10–74 mm

  Leaf blade orientation

  the upper surface of the leaf blade faces the stem of the plant

  Leaf blade shape

  • the leaf blade is lanceolate (lance-shaped; widest below the middle and tapering at both ends)
  • the leaf blade is linear (very narrow with more or less parallel sides)
  • 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 tip

  • the tip of the leaf blade is acute (sharply pointed)
  • the tip of the leaf blade is obtuse (bluntly pointed)

  Leaf blade veins

  the lateral veins are parallel or slightly arched in the direction of the tip

  Leaf blade width

  2–5 mm

  Leaf stalk length

  12–95 mm

  Leaf type

  the leaves are simple (lobed or unlobed but not separated into leaflets

  Leaflet number

  0

  Stipule twining

  NA

  Stipules

  there are no stipules on this plant

• Place

  Habitat

  wetlands

  New England state

  • Connecticut
  • Massachusetts

  Specific habitat

  • edges of wetlands
  • shores of rivers or lakes

• Scent

  Plant odor

  the leaves have no particular smell

• Stem, shoot, branch

  Flowering stem growth form

  the flowering stem is held upright

  Flowering stem leaves

  there are no true leaves on the flowering stem

  Stem hairs

  the stem is nearly or completely hairless

Wetland status

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

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae