Weed Information: Astragalus bisulcatus (milkvetch, twogrooved)
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Astragalus bisulcatus (milkvetch, twogrooved)

Family: Fabaceae

Description

Although the genus Astragalus is a very large and complicated group, most species can be readily determined when in fruit. In this species the fruit bears 2 longitudinal grooves; hence the common name. This is one of the most taxonomically difficult genera in North America. Virtually all of our species are non-weedy native wildflowers which have been included in weed books due to toxicity from alkaloids or selenium accumulation.

Characteristics

Flower Color
  • Blue
  • Blue-purple
  • Purple
  • White
  • Multi-colored
Inflorescence Type (How the flowers are arranged on the plant)
  • Axillary racemes
  • Terminal raceme
Number of Petals
  • 5 petals
Petal Separation
  • Completely free to base
  • United > 75% of length
Petal Tip
  • Pointed
  • Rounded
Flower Symmetry
  • Flowers strongly irregular
Flower Length (Head length in the Asteraceae)
  • 1.0 cm (.40 inch)
  • 1.5 cm (.6 inch)
Flower Width (Head width in the Asteraceae)
  • 5 mm (.20 inch)
  • 6 mm (.24 inch)
  • 7 mm (.28 inch)
  • 8 mm (.32 inch)
  • 9 mm (.36 inch)
  • 1.0 cm (.40 inch)
Number of Sepals
  • 5 sepals
Sepal Separation
  • United > 75% of length
Sepal Tip
  • Pointed
Flower Sex
  • Bisexual (perfect)
Number of Styles
  • 1 style
Number of Stamens
  • 10 stamens
Stamens Attached to the Petals
  • Stamens NOT attached to the petals
Stamens Connate (united)
  • Filaments united, diadelphous

Carpel Separation
  • Carpels united (or one)
Number of Carpels
  • 1 carpel
Ovary Position
  • Superior (hypogynous)
Fruit Type
  • Capsule, 1-celled
  • Legume
Fruit Length at Maturity
  • 1.5 cm (.60 inch)
  • 2.0 cm (.80 inch)
  • 2.5 cm (1.0 inch)
Fruit Width at Maturity
  • 1 mm (.04 inch) or less
  • 2 mm (.08 inch)
  • 3 mm (.12 inch)
  • 4 mm (.16 inch)
Burs
  • Fruit or seed NOT bur-like

Leaf Arrangement
  • Alternate
Leaf Type
  • Compound odd pinnate > 8 leaflets
Stipules
  • Foliaceous 2-4 mm (.08 - .16 in) long
  • Foliaceous 4-10 mm (.16 - .40 in) long
Tendrils
  • Tendrils absent
Venation
  • Pinnate
Petiole (leaf stem) Blade Ratio
  • Petiole < 25% total length
Leaf Length (blade PLUS petiole)
  • 2 - 4 cm (.80 - 1.60 inches)
  • 4 - 10 cm (1.60 - 4.0 inches)
  • 1 - 2 dm (4.0 - 8.0 inches)
Leaf Width
  • 1 - 2 cm (.40 - .80 inch)
  • 2 - 4 cm (.80 - 1.6 inches)
  • 4 - 10 cm (1.6 - 4.0 inches)
Leaf or Leaflet Margin
  • Entire
Leaf or Leaflet Blade Base
  • Acute (cuneate)
Leaf or Leaflet Tip
  • Acute
  • Mucronate
  • Rounded (obtuse)
Leaf or Leaflet Blade Surface
  • Strigose
Succulence
  • Not succulent

Milky Juice
  • Juice NOT milky (watery)
Woodiness
  • Herbaceous
Spines or Thorns
  • Spines or Thorns ABSENT
Aromatic (vegetative structures)
  • Not aromatic
Life Cycle
  • Perennial
Growth Habit (while flowering)
  • Spreading ascending
  • Erect, spherical (bushy)
Plant Height at Maturity
  • 2 - 4 dm (8.0 - 16.0 inches)
  • 4 - 6 dm (1.3 - 2.0 feet)
  • 6 - 8 dm (2.0 - 2.6 feet)
Wind Dissemination
  • Not wind disseminated
Moisture Regime
  • Mesic
  • Arid
Chlorophyll
  • Present

Stem Cross Section
  • Round
Flowering Stem Leaves
  • Stem uniformly leafy
Main Stem Branches
  • Main stem branched

Root or Vegetative Propagule
  • Tap Root

US State
  • Kansas
  • Arizona
  • Colorado
  • Idaho
  • Montana
  • North Dakota
  • New Mexico
  • Nevada
  • Oklahoma
  • South Dakota
  • Utah
  • Wyoming
  • Nebraska
Canadian Province or Territory
  • Alberta
  • Manitoba
  • Saskatchewan

  • Common Weeds of the Canadian Prairies, 1963 (Cat# A53-1136-1) See page: 25
  • Weeds and Poisonous Plants of Wyoming and Utah 1987 (ISBN 0-941570-06-1) See page: 66
  • Weeds of Alberta, 1983 Alberta Environmental Centre Agdex 640-4, See page: 83
  • Weeds of Colorado, 1990 Cooperative Extension, Colorado State Univ. Bulletin 521A, See page: 93
  • Weeds of the Prairies, 2000 Alberta Food and Agriculture ISBN# 0-7732-6147-8 See page: 42
  • Weeds of the West, 1992 (ISBN 0941570-13-4) See page: 322
  • Weeds of the West, 2000 (ISBN 0941570-13-4) See page: 320
  • Listed as a `Weed` by the Biota of North America Program, 2008 X
  • Listed in the WSSA Composite List of Weeds X
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