Your help is appreciated. We depend on donations to help keep this site free and up to date for you. Can you please help us?

Donate

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

Robinia pseudoacacia — black locust

Copyright: various copyright holders. To reuse an image, please click it to see who you will need to contact.

Facts

Black locust is native to parts of North America, but has greatly increased its range, being widely planted as a hardy street tree and for erosion control. It has an upright, narrow crown, widest at the top, producing masses of white, fragrant pea-like flowers that mature into flat pods in the fall. The ropy brown bark and red spines that line the new shoots also distinguish this locust from its relatives. Black locust thrives on nutrient-poor sites because it teams up with a bacterium that fixes nitrogen from the soil. Because it suckers readily and spreads widely, it has become invasive in certain portions of its range.

Habitat

Anthropogenic (man-made or disturbed habitats), floodplain (river or stream floodplains), forest edges, meadows and fields

New England distribution

Adapted from BONAP data

Found this plant? Take a photo and post a sighting.

North America distribution

Adapted from BONAP data

enlarge

Characteristics

Habitat
terrestrial
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Growth form
  • the plant is a shrub (i.e., a woody plant with several stems growing from the base)
  • 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 no teeth or lobes
Leaf duration
the leaves drop off in winter (or they wither but persist on the plant)
armature on plant
the plant has spines, prickles, or thorns
Leaf blade length
200–300 mm
Leaf stalk
the leaves have leaf stalks
Fruit type (general)
the fruit is dry and splits open when ripe
Bark texture
the bark of an adult plant is ridged or plated
Twig winter color
  • brown
  • gray
  • purple
  • red
Bud scale number
there are no scales on the winter buds
Show all characteristics

  • Buds or leaf scars

    Bud position relative to scar
    the winter bud has a leaf scar partially or completely surrounding it
    Bud scale number
    there are no scales on the winter buds
    Bud scar shape (Fraxinus)
    NA
    Collateral buds
    there are no collateral buds on the sides of the branches
    Leaf scar arrangement
    there is one leaf scar per node on the stem or twig
    Superposed buds
    • there are no superposed buds on the branch
    • there are superposed buds above the main (terminal) bud
    Winter bud scales
    the winter bud is naked (not covered with scales)
    Winter bud stalks
    the winter buds have no stalks

  • Flowers

    Carpels fused
    the carpel is solitary or (if 2 or more) the carpels are not fused to one another
    Enlarged sterile flowers
    there are no enlarged sterile flowers on the plant
    Flower petal color
    white
    Flower symmetry
    there is only one way to evenly divide the flower (the flower is bilaterally symmetrical)
    Hairs on ovary (Amelanchier)
    NA
    Hypanthium present
    the flower has a hypanthium
    Inflorescence hairs
    there are hairs on some part of the inflorescence
    Inflorescence position
    the inflorescences grow on the twigs
    Inflorescence type
    the inflorescence is a raceme (a long unbranched stem with stalked flowers growing along it)
    Number of pistils
    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 fusion
    • the perianth parts are fused to form a tube, cup, or bell shape
    • the perianth parts are separate
    Sepal cilia (Ilex)
    NA
    Sepal tip glands
    there are no glands at the tips of the sepal lobes
    Sepals fused only to sepals
    the sepals are fused to each other (not other flower parts), at least near their bases
    Stamen number
    10
    Stamen position relative to petals
    NA
    Stamens fused
    the stamens are fused to one another at or near their bases

  • Fruits or seeds

    Berry color
    NA
    Fruit tissue origin
    • the hypanthium of the flower becomes part of the fruit
    • there are no flower parts that form part of the fruit
    Fruit type (general)
    the fruit is dry and splits open when ripe
    Fruit type (specific)
    legume
    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 shrub (i.e., a woody plant with several stems growing from the base)
    • the plant is a tree

  • Leaves

    Hairs on underside of leaf blade
    the underside of the leaf has no hairs
    Hairs on upper side of leaf blade
    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 rounded
    Leaf blade base symmetry
    the leaf blade base is symmetrical
    Leaf blade bloom
    the underside of the leaf has no noticeable bloom
    Leaf blade edges
    the edge of the leaf blade has no teeth or lobes
    Leaf blade edges (Acer)
    NA
    Leaf blade flatness
    the leaf is flat (planar) at the edges
    Leaf blade hairs
    the hairs on the leaf blade are different from the choices given
    Leaf blade length
    200–300 mm
    Leaf blade scales
    there are no scales on the leaf blades
    Leaf blade shape
    • the leaf blade is elliptic (widest near the middle and tapering at both ends)
    • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)
    Leaf blade texture
    the leaf blade is herbaceous (has a leafy texture)
    Leaf blade translucent dots
    there are no translucent dots on the leaf blade
    Leaf blade vein pattern
    the main veins of the leaf blade are pinnate (the secondary veins branch off at intervals from the main central vein) and non-arcuate (not arched towards the leaf tip)
    Leaf blade veins
    the leaf blade has one main vein running from the base toward the tip
    Leaf duration
    the leaves drop off in winter (or they wither but persist on the plant)
    Leaf form
    the plant is broad-leaved (with broadly flattened leaf blades)
    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 attachment to leaf
    the petiole attaches at the basal margin of the leaf blade
    Leaf stalk nectaries
    there are no nectaries on the leaf stalk
    Leaf stalk shape
    the leaf stalk is not flattened
    Leaf teeth
    the edge of the leaf blade is entire (has no teeth or lobes)
    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
    Stipules
    the plant has stipules

  • Place

    Habitat
    terrestrial
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • edges of forests
    • man-made or disturbed habitats
    • meadows or fields
    • river or stream floodplains

  • Scent

    Plant odor
    the plant does not have much of an odor, or it has an unpleasant or repellant 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
    Lenticels on twigs
    there are clearly lenticels on the twigs
    Pith shape
    the outline of the pith in a twig is roughly round
    Short shoots
    there are no peg- or knob-like shoots present
    Twig bloom
    there is no bloom on the twig
    Twig hairs
    the twigs have few or no hairs on them
    Twig papillae (Vaccinium species only)
    NA
    Twig scales
    there are no scales on the twig surface
    Twig winter color
    • brown
    • gray
    • purple
    • red
    Wings on branch
    the branch does not have wings on it
    armature on plant
    the plant has spines, prickles, or thorns

Wetland status

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

In New England

Distribution

Connecticut
present, invasive
Maine
present, prohibited
Massachusetts
present, invasive, prohibited
New Hampshire
present
Rhode Island
present
Vermont
present

Conservation status

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

Connecticut
not applicable (S-rank: SNA)
Massachusetts
not applicable (S-rank: SNA)

From Flora Novae Angliae dichotomous key

2.  Robinia pseudoacacia L. E

black locust. CT, MA, ME, NH, RI, VT. Roadsides, forest fragments, field edges, riparian forests.

1×2. Robinia hispida × Robinia pseudoacacia → Robinia ×margarettae Ashe is a very rare locust hyrid known from MA. The shrubs to small trees (1–10 m tall) are hispid in the inflorescence and may be hispid on the petioles. The inflorescences contain 6–10 flowers with pink corollas. The fruits, when formed, are hispid or tuberculate on the outer surface.

Native to North America?

Yes and no (some introduced)

Family

Fabaceae

Genus

Robinia