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Robinia hispida — bristly locust

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Facts

Bristly locust is a 2-10 foot (0.7-3.5m) tall shrub, native to southeastern North America and introduced in other areas including New England. It is also called rose acacia for its showy sprays of pink, pea-like flowers. Its stems and seed pods are bristly and purple. It spreads abundantly by suckering, and as such, is useful as a hedge or screen and for reclaiming eroded sites. It is vulnerable to breakage and a variety of diseases, however, so it must be tended carefully.

Habitat

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

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
terrestrial
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Growth form
the plant is a shrub (a woody plant with several stems growing from the base)
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
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 does not have spines, prickles, or thorns
  • the plant has spines, prickles, or thorns
Leaf blade length
150–300 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 thin and smooth
Twig winter color
  • brown
  • gray
  • 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 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
    • pink
    • purple
    • red
    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 (a woody plant with several stems growing from the base)

  • 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 cuneate (wedge-shaped, tapers to the base with relatively straight, converging edges), or narrow
    • the base of the leaf blade is rounded
    • the base of the leaf blade is truncate (ends abruptly in a more or less straight line as though cut off)
    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
    150–300 mm
    Leaf blade scales
    there are no scales on the leaf blades
    Leaf blade shape
    • the leaf blade is oblong (rectangular but with rounded ends)
    • the leaf blade is orbicular (roughly circular, as wide as long)
    • 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 (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
    there are no stipules on the plant, or they fall off as the leaf expands

  • Place

    Habitat
    terrestrial
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • 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

  • Stem, shoot, branch

    Aerial roots
    the plant has no aerial roots
    Bark texture
    the bark of an adult plant is thin and smooth
    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 hairs with glands at their tips
    Twig papillae (Vaccinium species only)
    NA
    Twig scales
    there are no scales on the twig surface
    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
    • the plant has spines, prickles, or thorns

Wetland status

Not classified

In New England

Distribution

Connecticut
present
Maine
present
Massachusetts
present
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.

Massachusetts
unranked (S-rank: SNR)

var. hispida

Massachusetts
unranked (S-rank: SNR)

Subspecies and varieties

Robinia hispida L. var. hispida is known from CT, MA, ME, NH, RI, VT. R. hispida var. fertilis (Ashe) Clausen is known from CT.

From Flora Novae Angliae dichotomous key

1.  Robinia hispida L. E

bristly locust.  1a. Robinia fertilis Ashe; R. grandiflora Ashe;  1b. Robinia pallida Ashe; 
 R. speciosa Ashe • CT, MA, ME, NH, RI, VT. Roadsides, field edges, abandoned homesteads.

1a.  Plants producing abundant fruit; leaflets elliptic to elliptic-oblong or elliptic-obovate, acute to obtuse at the apex, at least sparsely pubescent abaxially, 7–25 mm wide; flowers 20–25 mm long … 1a. Robinia hispida var. fertilis (Ashe) Clausen

1b.  Plants rarely fruiting, and when fruits are produced these are often without seeds; leaflets oval to suborbicular, rounded to obtuse at apex, ± glabrous abaxially, 15–45 mm wide; flowers 25–30 mm long … 1b. Robinia hispida var. hispida

Variety fertilis is known from CT. This variety was reported from RI by Kartesz (1999), based on George (1992); however, George (1999) stated it had questionable naturalization in RI. Variety hispida is known from CT, MA, ME, NH, RI, VT.

Native to North America?

Yes

Sometimes confused with

Robinia viscosa:
leaves with 13-25 leaflets and glands on branchlets unstalked or nearly so (vs. R. hsipida, with leaves with 7-13 leaflets and glands on branchlets borne on evident bristles).

Synonyms

  • Robinia pallida Ashe
  • Robinia speciosa Ashe

Family

Fabaceae

Genus

Robinia