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• Dioscorea polystachya

Dioscorea polystachya — Chinese yam

Facts

Chinese yam, native to east Asia, is planted as a garden ornamental in North America. It is occasionally found in waste areas, compost piles or fields in Connecticut, Massachusetts and Vermont. The stems twine in a clockwise direction.

Habitat

Anthropogenic (man-made or disturbed habitats), meadows and fields

Characteristics

• Clonal plantlets

  Axillary bulblets

  there are bulblets in some axils

• Flowers

  Anther attachment

  the anther is attached by its base to the filament

  Bulblets replace flowers

  there are no bulblets where the flowers are located

  Carpels fused

  the carpels are fused (the number of carpels equals the number of locules)

  Flower bracts

  there are bracts associated with the flower

  Flower number

  1–8

  Flower orientation

  the flowers point upward or spread or curve outward

  Flower petal color

  • green to brown
  • white
  • yellow

  Flower petal length

  13–20 mm

  Flower shape

  • the flower is bell-shaped
  • the flower is cup-shaped

  Flower symmetry

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

  Form of style

  the style is branched above the base

  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

  20–100 mm

  Inflorescence type

  • the flowers grow out of the axil (point where a branch or leaf is attached to the main stem)
  • the inflorescence is a spike (a long unbranched stem with flowers along it that lack stalks)
  • the inflorescence is in the form of a compact cluster of flowers

  Length of flower stalk

  At least 0 mm

  Length of peduncle

  0 mm

  Marks on petals

  the petals have spots or streaks on them

  Nectar spur

  the flower has no nectar spurs

  Number of carpels

  3

  Number of pistils

  3

  Number of sepals and/or petals

  there are six petals, sepals or tepals in the flower

  Number of styles

  3

  Ovary position

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

  Petal and sepal arrangement

  the flower includes only one cycle of petals or sepals

  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 fusion

  • the perianth parts are fused to form a tube, cup, or bell shape
  • the perianth parts are separate

  Petal hairs on inner/upper surface

  there are no hairs on the inner/upper petal surface

  Petal nectaries

  there are nectaries at the petal bases

  Sepal appearance

  the sepals resemble petals in color and texture

  Sepal length

  1.3–2 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 fused to each other (often along with the petals in monocots), at least near their bases
  • the sepals are separate from one another

  Spathe

  the plant does not have a spathe

  Spathe form

  NA

  Spathe length

  0 mm

  Stamen number

  6

  Stamen position relative to petals

  NA

  Stamen types

  the stamens within a cycle are distinctly of two types

  Stamens fused

  the stamens are fused to one another at or near their bases

  Stamens fused outwards

  the stamens are fused to the petals or tepals at or near their bases

  Style petal-like

  the style is not broad and flattened like a petal

  Tepals

  the petals and sepals are similar in size and color

• Fruits or seeds

  Berry color

  NA

  Capsule ridges

  there are three ribs or wings on the capsule

  Fruit compartments

  there are three locules in the fruit

  Fruit length

  12–20 mm

  Fruit type (general)

  the fruit is dry and splits open when ripe

  Fruit type (specific)

  the fruit is a capsule (splits along two or more seams, apical teeth or pores when dry, to release two or more seeds)

  Fruit width

  12–20 mm

  Other markings on berry

  NA

• Glands or sap

  Sap

  the sap is clear and watery

• Growth form

  Lifespan

  the plant lives more than two years

  Root septa

  the roots do not have transverse septa

  Underground organs

  the plant has one or more swollen storage organs underground, such as bulbs, tubers or corms

• 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

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

  Leaf blade basal lobes

  the leaf blades are lobed at their bases

  Leaf blade base

  the leaf has a distinct leaf stalk (petiole)

  Leaf blade base shape

  • The base of the leaf blade is cordate (heart-shaped, with rounded lobes) or sagittate (arrow-shaped, with pointed, backward-facing lobes)
  • the base of the leaf blade is truncate (ends abruptly in a more or less straight line as though cut off)

  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

  30–90 mm

  Leaf blade orientation

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

  Leaf blade shape

  • the leaf blade is cordate (heart-shaped with backward-facing rounded lobes), or sagittate (arrow-shaped with backward-facing pointed lobes)
  • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)
  • the leaf blade is triangular, with the stalk or attachment point on one of the sides

  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 acuminate (tapers to a long, thin point)
  • the tip of the leaf blade is caudate (has a very long tail-like projection ending in a point)

  Leaf blade veins

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

  Leaf blade width

  30–110 mm

  Leaf stalk length

  20–30 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

  terrestrial

  New England state

  • Connecticut
  • Massachusetts
  • Vermont

  Specific habitat

  • man-made or disturbed habitats
  • meadows or fields

• Scent

  Plant odor

  the leaves have no particular smell

• Stem, shoot, branch

  Flowering stem growth form

  the flowering stem trails along the ground or on other vegetation, or floats in the water

  Flowering stem leaves

  there is at least one fully-formed leaf on the flowering stem

  Stem hairs

  the stem is nearly or completely hairless

Wetland status

Not classified

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae