Weed Information: Astragalus mollissimus (loco, wooly)
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Astragalus mollissimus (loco, wooly)

Family: Fabaceae

Description

A native, perennial legume from a woody taproot. The leaves odd pinnately compound with 15-33 leaflets. The flowers yellowish to purple in dense 10-40 flowered racemes. Very toxic to all classes of livestock. 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. There are several varieties of this species and all are lumped together in these photos and description.

Characteristics

Flower Color
  • Yellow
  • Purple
  • Red-purple
  • Multi-colored
Inflorescence Type (How the flowers are arranged on the plant)
  • Terminal raceme
Number of Petals
  • 5 petals
Petal Separation
  • Completely free to base
  • United > 75% of length
Petal Tip
  • Bilobed
  • Rounded
Flower Symmetry
  • Flowers strongly irregular
Flower Length (Head length in the Asteraceae)
  • 1.5 cm (.6 inch)
  • 2.0 cm (.8 inch)
  • 2.5 cm (1.0 inch)
Flower Width (Head width in the Asteraceae)
  • 8 mm (.32 inch)
  • 9 mm (.36 inch)
  • 1.0 cm (.40 inch)
  • 1.5 cm (.60 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)
Fruit Width at Maturity
  • 4 mm (.16 inch)
  • 5 mm (.20 inch)
  • 6 mm (.24 inch)
  • 7 mm (.28 inch)
Burs
  • Fruit or seed NOT bur-like

Leaf Arrangement
  • Alternate
Leaf Type
  • Compound odd pinnate > 8 leaflets
Stipules
  • Foliaceous 4-10 mm (.16 - .40 in) long
  • Foliaceous > 1 cm (> .40 inch) long
Tendrils
  • Tendrils absent
Venation
  • Pinnate
Petiole (leaf stem) Blade Ratio
  • Petiole < 25% total length
Leaf Length (blade PLUS petiole)
  • 4 - 10 cm (1.60 - 4.0 inches)
  • 1 - 2 dm (4.0 - 8.0 inches)
  • 2 - 4 dm (8.0 - 16.0 inches)
Leaf Width
  • 1 - 2 cm (.40 - .80 inch)
  • 2 - 4 cm (.80 - 1.6 inches)
Leaf or Leaflet Margin
  • Entire
Leaf or Leaflet Blade Base
  • Rounded
Leaf or Leaflet Tip
  • Rounded (obtuse)
Leaf or Leaflet Blade Surface
  • Sericeous or villous (silky)
  • Tomentose
  • Villous or sericious (silky)
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
  • 1 - 5 cm (.40 - 2.0 inches)
  • 5 - 10 cm (2.0 - 4.0 inches)
  • 1 - 2 dm (4.0 - 8.0 inches)
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
  • Texas
  • Arizona
  • Colorado
  • New Mexico
  • Nevada
  • Oklahoma
  • South Dakota
  • Utah
  • Wyoming
  • Nebraska

  • Common Weeds of the United States, 1971 (ISBN 0-486-20504-5) See page: 226
  • Field Guide To The Common Weeds Of Kansas, 1983 (ISBN 0-7006-0233-X) See page: 57
  • Nebraska Weeds, 1979 Nebraska Dept. of Ag., Lincoln NE, See page: 105
  • Weed Seeds of the Great Plains, 1993 University of Kansas# 92-125-B ISBN# 0-7006-0651-3 See index #: 92
  • Weeds, 1955 (1980) Walter Conrad Muenscher, ISBN# 0-8014-1266-8 See page: 290
  • Weeds, A Golden Guide, 1972 ISBN#0-307-24353-2 See page: 71
  • Weeds of Nebraska and the Great Plains, 1994 (ISBN 0939870-00-4) See page: 300
  • 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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