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• Aquatic plants
• Water plants with leaves and stems
• Trapa natans

Trapa natans — water-chestnut

Facts

Water-chestnut is an aquatic annual, native to Europe and Asia, where it is a component of many regional cuisines. Introduced in North America, it first appeared near Concord, Massachusetts in 1859. Water-chestnut can be quite invasive in the Northeast, and is classified as such in most New England states. It grows in shallow water of lakes and rivers. Control is expensive and, due to the longevity of seeds, somewhat unreliable.

Habitat

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

Characteristics

• Flowers

  Flower lower lip length

  0 mm

  Flower number

  1

  Flower position

  the flowers are above the surface of the water

  Flower symmetry

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

  Inflorescence type

  • the flowers grow out of the axil (point where a branch or leaf is attached to the main stem)
  • the inflorescence has only one flower on it

  Nectar spur

  the flower has no nectar spurs

  Number of carpels

  2

  Ovary position

  the sepals and/or petals are attached above the ovary

  Palate on corolla

  NA

  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 color

  white

  Petal fringed edges

  the petals are not fringed

  Petal hairs on inner/upper surface

  there are no hairs on the inner/upper petal surface

  Petal length

  7–10 mm

  Petal number

  4

  Petal or sepal number

  there are four petals, sepals, or tepals in the flower

  Sepal appearance

  the sepals resemble leaves in color and texture

  Sepal number

  4

  Sepals fused only to sepals

  • the sepals are fused to each other (not other flower parts), at least near their bases
  • the sepals are separate from one another

  Spur length

  0 mm

  Stamen number

  4

  Stamen position relative to petals

  the stamens are lined up with the sepals

  Stamens fused to petals

  the stamens are fused near the bases of the petals or tepals

  Style number

  1

• Fruits or seeds

  Fruit length

  18–30 mm

  Fruit type (general)

  the fruit is dry but does not split open when ripe

  Fruit type (specific)

  the fruit is a nut (dry and indehiscent, with a hard wall, usually containing only one seed and usually subtended by an involucre)

  Fruit width

  20–45 mm

• Glands or sap

  Sap

  the sap is clear and watery

• 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

  Bract position (Sparganium)

  NA

  Floating leaf basal lobes

  no

  Floating leaf blade width

  40–80 mm

  Floating leaf length

  40–60 mm

  Floating leaf shape

  the leaf blade is triangular, with the stalk or attachment point on one of the sides

  Leaf arrangement

  • alternate: there is one leaf per node along the stem
  • opposite: there are two leaves per node along the stem

  Leaf blade length

  40–60 mm

  Leaf blade veins

  the lateral veins radiate from the base and continue to spread away from the centerline of the leaf, or branch off the central vein at intervals

  Leaf blade width

  40–80 mm

  Leaf position

  • some of the leaves are floating at the surface of the water
  • the leaves are all submerged underwater

  Leaf special features

  the leaves have inflated petioles or blades that help them float

  Leaf-like branch segments

  0

  Specific leaf type

  the leaf is not divided, rather the blade is made up of one segment

  Staminate bract edge (Myriophyllum)

  NA

  Stipules

  the plant has stipules

  Trap-bladder length

  0 mm

  Underwater leaf blade edges

  the underwater leaf has smooth edges, without teeth

  Underwater leaf blade shape

  the underwater leaf blade is capillary (very fine and hair-like)

  Underwater leaf blade width

  40–80 mm

  Underwater leaf length

  40–60 mm

  Underwater leaf stalk

  no

  Underwater leaf stalk length

  20–180 mm

  Underwater leaf tip shape

  the tip of the underwater leaf is acute (sharply pointed)

  Veins in floating leaf

  anything

• Place

  Habitat

  aquatic

  New England state

  • Connecticut
  • Massachusetts
  • New Hampshire
  • Vermont

  Specific habitat

  • in lakes or ponds
  • in rivers or streams

• Stem, shoot, branch

  Flowering stem growth form

  the flowering stem trails along the substrate, or floats in the water

Wetland status

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

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae