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Juglans ailantifolia — Japanese walnut

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New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Facts

Japanese walnut, a native to Asia, is recorded as naturalized only in Massachusetts, Rhode Island, and West Virginia. Its species name, "ailantifolia" suggests a resemblance of the leaves to Tree-of-Heaven (Ailanthus altissima), although a close comparison of these two says that would be a stretch. Juglans ailantifolia is resistent to canker fungus that has attacked native butternut (Juglans cinerea), and has become a popular street tree. It can hybridize with butternut, and nurseries are trying several backcrosses to breed a more resistant butternut. The wood of this species is used in making furniture.

Habitat

Anthropogenic (man-made or disturbed habitats), forest edges, forests

Characteristics

Habitat
terrestrial
New England state
  • Massachusetts
  • Rhode Island
Growth form
the plant is a tree
Leaf type
the leaf blade is compound (i.e., made up of two or more discrete leaflets
Leaves per node
there is one leaf per node along the stem
Leaf blade edges
the edge of the leaf blade has teeth
Leaf duration
the leaves drop off in winter (or they wither but persist on the plant)
armature on plant
the plant does not have spines, prickles, or thorns
Leaf stalk
the leaves have leaf stalks
Fruit type (general)
the fruit is dry but does not split open when ripe
Bark texture
the bark of an adult plant is ridged or plated
Twig winter color
  • brown
  • gray
Bud scale number
there are two scales on the winter bud, and their edges meet
Show all 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

  • 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
    • 10
    • 11
    • 12
    • 13 or more
    • 7
    • 8
    • 9
    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 have glands at their tips
    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 obovate (egg-shaped, but with the widest point above the middle of the leaf blade)
    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 (i.e., 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
    • Massachusetts
    • Rhode Island
    Specific habitat
    • edges of forests
    • forests
    • man-made or disturbed habitats

  • 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
    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

Not classified

New England distribution and conservation status

Distribution

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

Conservation status

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

Massachusetts
not applicable (S-rank: SNA)

Native to North America?

No

Sometimes confused with

Juglans cinerea:
branchlets with dark brown pith, with relatively thick diaphragms that are nearly as broad as the chambers they alternate with, upper margin of leaf scar straight or scarcely notched, and exterior of endocarp strongly 6- to 8-ridged and with irregular, +/- sharp crests and projections (vs. J. ailantifolia, with branchlets with light brown pith, with thin diaphragms that are much narrower than the chambers they alternate with, upper margin of leaf scar with a conspicuous notch, and exterior of endocarp rugose).

Synonyms

  • Juglans sieboldiana Maxim.

Family

Juglandaceae

Genus

Juglans

Help

From the dichotomous key of Flora Novae Angliae

1.  Juglans ailantifolia Carr. E

Japanese walnut. Juglans sieboldiana Maxim. • MA, RI. Roadsides, forest fragments, areas of habitation. This species was reported for ME by Magee and Ahles (1999), but the collections were taken from planted trees—7 Jul 1948, Bicknell s.n. ( MAINE!).

1×2. Juglans ailantifolia × Juglans cinerea → Juglans ×‌bixbyi Rehd. This infrequent walnut hybrid is known from ct, mA (and likely found in other states). It is most common in the planted setting along streets and in yards, but naturalized populations have been observed. The hybrid is intermediate between its two parental species. This is perhaps best evidenced in the exterior of the endocarp (i.e., the shell), which is ridged, but not as prominently as in J. cinerea.