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• Dichotomous Key
• Juglandaceae
• Juglans
• Juglans nigra

Juglans nigra — black walnut

Facts

Black walnut is one of the most highly prized trees of the North American flora -- for its edible walnuts and its exceptionally beautiful wood with darkly patterned grain. It was a dominant and majestic canopy species of primeval midwestern and southeastern forests, attaing heights of 150 feet (50 m) or more. But clearing for agriculture and harvesting for making railroad ties, gunstocks, log cabins, cradles, veneer, and cabinets decimated the species. Its glossy, mostly hairless leaves and twigs with light-brown pith distinguish black walnut from other Juglans species. Chemicals exuded from its roots may inhibit the growth of other plants.

Habitat

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

Characteristics

• Buds or leaf scars

  Bud scale number

  there are two scales on the winter bud, and their edges meet

  Bud scar shape (Fraxinus)

  NA

  Collateral buds

  there are no collateral buds on the sides of the branches

  Superposed buds

  there are no superposed buds on the branch

• Flowers

  Carpels fused

  the carpels are fused to one another

  Enlarged sterile flowers

  there are no enlarged sterile flowers on the plant

  Flower petal color

  NA

  Flower symmetry

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

  Hairs on ovary (Amelanchier)

  NA

  Hypanthium present

  the flower does not have a hypanthium

  Inflorescence type

  • the inflorescence is a raceme (a long unbranched stem with stalked flowers growing along it)
  • the inflorescence is an ament (catkin; slender, usually pendulous inflorescence with crowded unisexual flowers)

  Number of pistils

  1

  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

  NA

  Petal fusion

  NA

  Sepal cilia (Ilex)

  NA

  Stamen number

  13 or more

  Stamen position relative to petals

  NA

• Fruits or seeds

  Berry color

  NA

  Fruit tissue origin

  there are no flower parts that form part of the fruit

  Fruit type (general)

  the fruit is dry but does not split open when ripe

  Fruit type (specific)

  • the fruit is a drupe (fleshy, with a firm inner ovary wall that encloses a single seed)
  • the fruit is a nut (dry and indehiscent, with a hard wall, usually containing only one seed and usually subtended by an involucre)

  Nut with spines (Fagaceae)

  NA

  Wings on fruit

  there are no wings on the fruit

• Glands or sap

  Sap color

  the sap is clear and watery

  Stalked glands on fruit (Rosa)

  NA

• Growth form

  Growth form

  the plant is a tree

• Leaves

  Hairs on upper side of leaf blade

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

  Leaf blade base shape

  the base of the leaf blade is truncate (ends abruptly in a more or less straight line as though cut off)

  Leaf blade edges

  the edge of the leaf blade has teeth

  Leaf blade edges (Acer)

  NA

  Leaf blade flatness

  the leaf is flat (planar) at the edges

  Leaf blade hairs

  • NA
  • at least some of the hairs on the leaf blade are branched
  • at least some of the hairs on the leaf blade have glands at their tips

  Leaf blade length

  200–600 mm

  Leaf blade scales

  • there are no scales on the leaf blades
  • there are scales on the leaf blades

  Leaf blade shape

  the leaf blade is oblong (rectangular but with rounded ends)

  Leaf blade texture

  • the leaf blade is coriaceous (has a firm, leathery texture)
  • the leaf blade is herbaceous (has a leafy texture)

  Leaf blade translucent dots

  there are no translucent dots on the leaf blade

  Leaf duration

  the leaves drop off in winter (or they wither but persist on the plant)

  Leaf lobe tips (Quercus)

  NA

  Leaf midrib glands

  the midrib of the leaf blade lacks glands on the upper surface

  Leaf stalk

  the leaves have leaf stalks

  Leaf stalk nectaries

  there are no nectaries on the leaf stalk

  Leaf teeth

  the leaf blade margin is serrate (with forward-pointing) or dentate (with outward-pointing) with medium-sized to coarse teeth

  Leaf teeth hairs (Carya)

  NA

  Leaf type

  the leaf blade is compound (made up of two or more discrete leaflets

  Leaves per node

  there is one leaf per node along the stem

  Specific leaf type

  the leaf is compound, with a single terminal leaflet and more than two additional leaflets

• Place

  Habitat

  terrestrial

  New England state

  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont

  Specific habitat

  • forests
  • man-made or disturbed habitats
  • meadows or fields

• Scent

  Plant odor

  • the plant does not have much of an odor, or it has an unpleasant or repellant odor
  • the plant has a pleasantly aromatic odor

• Stem, shoot, branch

  Aerial roots

  the plant has no aerial roots

  Bark texture

  the bark of an adult plant is ridged or plated

  Branch brittleness (willows only)

  NA

  Branch cross-section

  the branch is circular in cross-section, or it has five or more sides, so that there are no sharp angles

  First-year cane (Rubus)

  NA

  Pith type

  the pith inside the twig is chambered (there are hollow sections with walls between them)

  Twig papillae (Vaccinium species only)

  NA

  Twig winter color

  • brown
  • gray
  • red

  Wings on branch

  the branch does not have wings on it

  armature on plant

  the plant does not have spines, prickles, or thorns

Wetland status

Usually occurs in non-wetlands, but occasionally in wetlands. (Wetland indicator code: FACU)

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae