Astragalus robbinsii (Oakes) Gray

Robbins' milk-vetch

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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 About

Robbins' milk-vetch has a disjunct distribution in North America, with separate western and northeastern ranges. There are three varieties in New England that differ in range and conservation status. One of them (Astragalus robbinsii var. robbinsii) is now extinct. Another (A. robbinsii var. jesupii) is found only in three sites along the Connecticut River in New Hampshire and Vermont, on ice-scoured shores. The third (A. robbinsii var. minor) is found in Maine and Vermont.

Habitat

Cliffs, balds, or ledges, ridges or ledges, shores of rivers or lakes

Characteristics

Habitat
  • terrestrial
  • wetlands
Flower petal color
  • blue to purple
  • white
Leaf type
the leaves are compound (made up of two or more discrete leaflets
Leaf arrangement
alternate: there is one leaf per node along the stem
Leaf blade edges
the edge of the leaf blade is entire (has no teeth or lobes)
Flower symmetry
there is only one way to evenly divide the flower (the flower is bilaterally symmetrical)
Number of sepals, petals or tepals
  • there are five petals, sepals, or tepals in the flower
  • there are four petals, sepals, or tepals in the flower
Fusion of sepals and petals
the petals or the sepals are fused into a cup or tube
Fruit type (general)
the fruit is dry and splits open when ripe
Fruit length
13–25 mm
Show All Characteristics
  • Clonal plantlets
    Bulbils
    the plant does not appear to have bulbils
    Bulblets replace flowers
    there are no bulblets where the flowers are located
  • Flowers
    Anther opening
    the anthers have narrow slits or furrows that run lengthwise along the anthers
    Anther spurs
    the anthers do not have spurs on them
    Calyx symmetry
    there is only one way to evenly divide the calyx (the calyx is bilaterally symmetrical)
    Carpels fused
    • NA
    • the carpel is solitary or (if 2 or more) the carpels are not fused to one another
    Cleistogamous flowers
    there are no cleistogamous flowers on the plan
    Corolla morphology
    NA
    Corolla palate
    no
    Corona lobe length
    0 mm
    Epicalyx
    the flower does not have an epicalyx
    Epicalyx number of parts
    0
    Filament surface
    the filament is smooth, with no hairs or scales
    Flower description
    the flower has a superior ovary and a hypanthium
    Flower length
    17–22 mm
    Flower number
    At least 5
    Flower petal color
    • blue to purple
    • white
    Flower reproductive parts
    the flower has both pollen- and seed-producing parts
    Flower symmetry
    there is only one way to evenly divide the flower (the flower is bilaterally symmetrical)
    Flowers sunken into stem
    no
    Fused stamen clusters
    there are two clusters of fused stamens
    Fusion of sepals and petals
    the petals or the sepals are fused into a cup or tube
    Hairs on inflorescence
    the axis of the inflorescence has hairs entirely without glands
    Horns in hoods (Asclepias)
    NA
    Hypanthium
    the flower has a hypanthium
    Inflorescence length
    20–30 mm
    Inflorescence one-sided
    the flowers are arrayed in a spiral around the inflorescence axis or branches, or occur singly, or in several ranks
    Inner tepals (Rumex)
    NA
    Length of flower stalk
    1.5–5 mm
    Nectar spur
    the flower has no nectar spurs
    Number of carpels
    1
    Number of pistils
    1
    Number of sepals, petals or tepals
    • there are five petals, sepals, or tepals in the flower
    • there are four petals, sepals, or tepals in the flower
    Number of styles
    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 and sepal colors
    • blue to purple
    • white
    Petal appearance
    the petals are thin and delicate, and pigmented (colored other than green or brown)
    Petal base
    the petal narrows abruptly at the base
    Petal folding in bud
    • the petals in bud are arranged in a cycle with edges overlapping like roof shingles (imbricate)
    • the petals in bud meet exactly at the margins without overlapping (valvate)
    Petal folds or pleats
    • the petals of the flower do not have folds or plaits
    • the petals of the flower have folds or plaits on them
    Petal hairs (Viola)
    NA
    Petal length
    7–12 mm
    Petal number
    5
    Petal tip shape
    • the petal tip is acute (sharply pointed)
    • the petal tip is obtuse (bluntly pointed)
    Petal tips (Cuscuta)
    NA
    Raceme attachment (Veronica)
    NA
    Reproductive system
    all the flowers have both carpels and stamens (synoecious)
    Scales inside corolla
    no
    Sepal and petal color
    the sepals are different from the petals
    Sepal appearance
    the sepals are green or brown, and leaf-like in texture
    Sepal appendages
    the sepals do not have appendages on them
    Sepal appendages (Oenothera)
    NA
    Sepal color
    green to brown
    Sepal length
    3.5–7.5 mm
    Sepal number
    5
    Sepal orientation
    the sepals are pressed against the corolla, or jutting stiffly upward
    Sepal relative length
    the sepal lobes are shorter than the fused portion
    Sepal shape
    the sepal outline is subulate (narrowly tapering from the base to the apex; awl-shaped)
    Sepal texture
    NA
    Sepal tip shape
    the sepal tip is acuminate (tapers to a very narrow point)
    Sepal uniformity
    one or more of the sepals is much narrower or shorter than the others
    Sepals fused only to sepals
    the sepals are fused to each other (not other flower parts), at least near their bases
    Stamens fused
    the stamens are attached to one another at or near their bases
    Staminodes
    there are no staminodes on the flower
    Stigma position
    the stigmas are positioned at the tip of the style
    Style petal-like
    the styles are not petal-like
    Umbel flower reproductive parts
    NA
    Upper lip of bilabiate corolla
    NA
  • Fruits or seeds
    Achene relative orientation
    NA
    Achene shape
    NA
    Achene surface (Polygonum)
    NA
    Achene type
    NA
    Berry color
    NA
    Capsule color (Viola)
    NA
    Capsule ribs
    NA
    Capsule splitting
    • NA
    • the capsule splits by two main valves, teeth or pores
    Fruit (pyxis) dehiscence
    NA
    Fruit beak length
    0.5–3 mm
    Fruit cross-section
    the fruit is roughly triangular in cross-section
    Fruit features (Brassicaceae)
    NA
    Fruit length
    13–25 mm
    Fruit length relative to sepals
    the fruit is longer than its associated sepals
    Fruit locules
    one
    Fruit shape
    • the fruit is ellipsoid (widest in the middle and tapering to each end)
    • the fruit is obloid (longer than wide and with rounded ends)
    • the fruit is spherical
    Fruit type (general)
    the fruit is dry and splits open when ripe
    Fruit type (specific)
    the fruit is a legume (a fruit that splits into two valves, but only has a single carpel; think of a pea pod)
    Fruit width
    3.5–5.5 mm
    Hairs on fruit
    the fruits have hairs on them
    Legumes (Fabaceae)
    the legume has none of the mentioned special features
    Mericarp length
    0 mm
    Mericarp segment shape (Desmodium)
    NA
    Other markings on berry
    NA
    Ovary stipe
    • the ovary or fruit does not have a stipe
    • the ovary or fruit has a stipe
    Ovary stipe length
    0.5–5 mm
    Placenta arrangement
    the plant has parietal placentation, where ovules develop on the wall or slight outgrowths of the wall forming broken partitions within a compound ovary
    Rows of seeds in fruit (Brassicaceae)
    NA
    Schizocarpic fruit compression
    NA
    Schizocarpic fruit segments
    0
    Seed number
    3–11
    Septum in fruit (Brassicaceae)
    NA
    Wings on fruit
    the fruit does not have wings on it
    prickles on fruits
    the fruits do not have thorn-like defensive structures
  • Glands or sap
    Glands on leaf blade
    the leaf blades do not have glandular dots or scales
    Sap
    the sap is clear and watery
    Sap color
    the sap is clear
  • Growth form
    Growth form
    the plant is an herb (it has self-supporting stems)
    Lifespan
    the plant lives more than two years
    Parasitism
    the plant is not parasitic
    Plant color
    the leaves or young stems of the plant are green
    Plants darken when dry
    no
    Spines on plant
    the plant has no spines
    Underground organs
    • the plant has a caudex (the root mass is firm and hardened at the top)
    • there is a thickened taproot on the plant
  • Leaves
    Bracteole number (Apiaceae)
    0
    Bracteoles
    • the plant has bracteoles between the primary bracts and the flowers
    • there are no bracteoles on the plant
    Bracts in plantain (Plantago)
    NA
    Final leaf segment length (compound lvs only)
    5–20 mm
    Final leaf segment length to width ratio (compound lvs only)
    1.3–3.5
    Floral bracts
    • the flower does not have bracts
    • the flower has one or more bracts associated with it
    Hairs on underside of leaf
    • the underside of the leaf is fuzzy or hairy
    • the underside of the leaf is not hairy, or it has very few hairs
    Hairs on upper side of leaf
    the upper side of the leaf is not hairy, or it has very few hairs
    Hooked hairs on underside of leaf
    no
    Leaf arrangement
    alternate: there is one leaf per node along the stem
    Leaf blade base
    • the leaf has a distinct leaf stalk (petiole)
    • the leaf has no stalk
    Leaf blade base shape
    the base of the leaf blade is rounded
    Leaf blade base symmetry
    the leaf blade base is symmetrical
    Leaf blade edges
    the edge of the leaf blade is entire (has no teeth or lobes)
    Leaf blade flatness
    the leaf is flat (planar) at the edges
    Leaf blade primary vein pattern
    the secondary veins branch off at intervals from the primary vein
    Leaf blade shape
    • the leaf blade is elliptic (widest near the middle and tapering at both ends)
    • the leaf blade is lanceolate (lance-shaped; widest below the middle and tapering at both ends)
    • the leaf blade is oblong (rectangular but with rounded ends)
    • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)
    Leaf blade surface colors
    the upper side of the leaf blade is relatively uniform in color
    Leaf blade texture
    the leaf blade is herbaceous (has a leafy texture)
    Leaf blade veins
    the leaf blade has one main vein running from the base towards the tip (it may or may not have secondary veins)
    Leaf duration
    the leaves drop off in winter (or they whither but persist on the plant)
    Leaf form
    the leaves are green, with an expanded blade and a leaf-like texture
    Leaf hair orientation
    the hairs are flat against the leaf surface, mostly pointing towards the leaf tip
    Leaf shiny
    the upper side of the leaf is dull or slightly shiny
    Leaf spines
    there are no spines on the leaf edges
    Leaf stalk
    • the leaves have leaf stalks
    • the leaves have no leaf stalks, but attach directly to the stem
    Leaf stalk attachment to leaf
    the petiole attaches at the basal margin of the leaf blade
    Leaf stalk base
    the petiole base is narrow where it attaches to the stem
    Leaf stalk length
    0–90 mm
    Leaf teeth and lobes
    the edge of the leaf blade is entire (has no teeth or lobes)
    Leaf tip
    • the tip of the leaf blade is obtuse (bluntly pointed)
    • the tip of the leaf blade is retuse (blunt or rounded, with a notch at the tip)
    Leaf type
    the leaves are compound (made up of two or more discrete leaflets
    Leaf variation
    the leaves are nearly similar in size, prominence of teeth, and length of stalks throughout the stem
    Leaflet number
    7–17
    Leaflet petiolules
    the leaflets of the compound leaf lack petiolules
    Leaves per node
    there is one leaf per node along the stem
    Pinnately compound leaf type
    the pinnately compound leaves have a terminal leaflet (and usually have an odd number of leaflets per axis)
    Specific leaf type
    the leaf has a row of two or more lobes on each side of the central axis
    Stipels
    there are no stipels at the bases of the petiolules
    Stipule features
    NA
    Stipule fused to leaf stalk
    • the stipules are fused to the petioles for some or most of their length
    • the stipules are not fused to the petioles
    Stipules
    the plant has stipules
    Teeth per side of leaf blade
    0
  • Place
    Habitat
    • terrestrial
    • wetlands
    Specific habitat
    • cliffs, balds, or ledges
    • ridges or ledges
    • shores of rivers or lakes
  • Stem, shoot, branch
    Branched tendrils
    NA
    Hair between stem nodes
    • the stem has hairs between the nodes
    • the stem has no hairs between the nodes
    Hairs between stem nodes
    • the hairs on the stem are plain, without glands or branches, and not tangled
    • the stem has no hairs between the nodes
    Leaves on stem
    there is at least one full leaf above the base of the flowering stem
    Plant height
    10–50 cm
    Stem orientation
    the stems are upright or angled outwards
    Stem spacing
    the plant is growing in tufts, or compact clusters with closely spaced stems, or it is densely matted together in clumps, cushionlike
    Tendril origin
    NA
    Tendrils
    the plant does not have tendrils

Wetland Status

Occurs only in non-wetlands. (Wetland indicator code: UPL)

New England Distribution and Conservation Status

Distribution

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

Conservation Status

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

Maine
extremely rare (S-rank: S1)

var. jesupii

New Hampshire
extremely rare (S-rank: S1), endangered (code: E)
Vermont
extremely rare (S-rank: S1), endangered (code: E)

var. minor

Maine
extremely rare (S-rank: S1), endangered (code: E)
Vermont
rare (S-rank: S2)

var. robbinsii

Vermont
extirpated (S-rank: SX)

Native to North America?

Yes

Sometimes Confused With

Astragalus eucosmus:
legumes mostly 8-11 mm long, +/- sessile, and flowers 6-9 mm long (vs. A. robbinsii, with legumes legumes 13-25 mm long, on a stipe 2-5 mm long, and flowers mostly 10-12 mm long).
Astragalus alpinus:
principal leaves with 15-25 leaflets, keel petal not or only slightly shorter than the banner petal, and upper suture of fruit prominently sulcate (vs. A. robbinsii, with the principal leaves with mostly 7-15 leaflets, keel petal markedly shorter than the banner petal, and upper suture of fruit scarcely sulcate).

Synonyms

  • Phaca robbinsii Oakes

Family

Fabaceae

Genus

Astragalus

Notes on Subspecies and Varieties in New England

Variety robbinsii is known from VT. It is now extinct. Variety jesupii is known from NH, VT. Variety minor is known from ME, VT. All the infraspecific taxa are of regional conservation concern.

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Information from Dichotomous Key of Flora Novae Angliae

6.  Astragalus robbinsii (Oakes) Gray NC

Robbin’s milk-vetch. 6a. Phaca robbinsii Oakes; 6b. Astragalus jesupii (Egglest. & Sheldon) Britt.; 6c. Astragalus blakei Egglest.; A. robbinsii (Oakes) Gray var. blakei (Egglest.) Barneby 
• ME, NH, VT. River shore beaches and ledges, cliffs, and talus in regions of high-pH bedrock and/or till.

1a.  Flowers 7–9 (–10) mm long, usually with a white corolla; legume 10–15 mm long; plants historically documented from a single station on the Winooski River in vt

6a. A. robbinsii var. robbinsii

1b.  Flowers 10–12 mm long, usually with a light purple corolla; legume 15–25 mm long; plants not known from the Winooski River, vt

2a.  Legume tipped by a beak 1.5–3 mm long; leaflets glabrous or nearly so abaxially; plants known from the Connecticut River in NH and VT
 … 6b. A. robbinsii var. jesupii Egglest. & Sheldon

2b.  Legume scarcely beaked or with a projection up to 1.5 mm long; leaflets strigose abaxially; plants known from the mountains of northern vt and river shores of northern ME
 … 6c. A. robbinsii var. minor (Hook.) Barneby

Variety robbinsii is known from VT. It is now extinct. Variety jesupii is known from NH, VT. Variety minor is known from ME, VT. All the infraspecific taxa are of regional conservation concern.