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Native Plant Trust: Go Botany Discover thousands of New England plants

Helanthium tenellum — dwarf burhead

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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)

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
wetlands
New England state
  • Connecticut
  • Massachusetts
Leaf arrangement
basal: the leaves are growing only at the base 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 length
10–74 mm
Flower petal color
  • pink to red
  • white
Flower petal length
1–3 mm
Petal fusion
the perianth parts are separate
Inflorescence type
the inflorescence is an umbel (with an axis so short it appears the flowers all originate from the same point)
Ovary position
the ovary is above the point of petal and/or sepal attachment
Fruit type (specific)
the fruit is an achene (dry, usually 1-seeded, does not separate or split open at maturity)
Fruit length
0.8–1.5 mm
Show all 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
    basal: the leaves are growing only at the base of the plant
    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 (i.e., 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)

In New England

Distribution

Connecticut
present
Maine
absent
Massachusetts
present
New Hampshire
absent
Rhode Island
absent
Vermont
absent

Conservation status

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

Massachusetts
historical (S-rank: SH), H (code: H)
New Hampshire
unrankable (S-rank: SU), Ind (code: Ind)
Rhode Island
historical (S-rank: SH), state historical (code: SH)

From Flora Novae Angliae dichotomous key

1.  Helanthium tenellum (Mart.) Britt. NC

dwarf burhead. Alisma tenellum Mart.; Echinodorus parvulus Engelm.; E. tenellus (Mart.) Buch.; E. tenellus (Mart.) Buch. var. parvulus (Engelm.) Fassett; Helanthium parvulum (Engelm.) Small • CT, MA; also reported from ME by Perkins (1936) and from VT by Haynes and Hellquist (2000a), but specimens are unknown. Sandy shorelines of ponds and streams. The report from ME by Perkins was eventually retracted (1938), but the retraction was apparently not based on annotation of the original specimens but rather on an inability to find additional specimens (which could indicate the population was extirpated, not that the original collections were incorrectly determined).

Native to North America?

Yes

Sometimes confused with

Sagittaria graminea:
flowers with 6 stamens and single whorl of carpels, collectively arranged in a panicle (vs. H. tenellum, with flowers with around 9 stamens and multiple whorls of carpels, collectively arranged in an umbel).

Synonyms

  • Echinodorus parvulus Engelm.
  • Echinodorus tenellus (Mart.) Buch.
  • Echinodorus tenellus (Mart.) Buch. var. parvulus (Engelm.) Fassett
  • Helanthium parvulum (Engelm.) Small

Family

Alismataceae

Genus

Helanthium