Weed Information: Medicago sativa (alfalfa)
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Medicago sativa (alfalfa)

Family: Fabaceae

Description

While most commonly known as a cultivated crop, alfalfa also can be very weedy in disturbed habitats. The flowers are commonly blue-purple but can also be various combinations of blue, yellow, and white. Look for the coiled pod on last year`s growth for positive identification. Medicago falcata = Medicago sativa var. falcata

Characteristics

Flower Color
  • Yellow
  • Yellow-green
  • Blue
  • Blue-purple
  • Purple
  • White
  • Multi-colored
  • Blue-green
Inflorescence Type (How the flowers are arranged on the plant)
  • Axillary racemes
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)
  • 6 mm (.24 inch)
  • 7 mm (.28 inch)
  • 8 mm (.32 inch)
  • 9 mm (.36 inch)
  • 1.0 cm (.40 inch)
Flower Width (Head width in the Asteraceae)
  • 3 mm (.12 inch)
  • 4 mm (.16 inch)
  • 5 mm (.20 inch)
  • 6 mm (.24 inch)
Number of Sepals
  • 5 sepals
Sepal Separation
  • United from 25% - 75% 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
  • 7 mm (.28 inch)
  • 8 mm (.32 inch)
  • 9 mm (.36 inch)
Fruit Width at Maturity
  • 7 mm (.28 inch)
  • 8 mm (.32 inch)
  • 9 mm (.36 inch)
Burs
  • Fruit or seed NOT bur-like

Leaf Arrangement
  • Alternate
Leaf Type
  • Trifoliolate (3 leaflets)
Stipules
  • Foliaceous 4-10 mm (.16 - .40 in) long
Tendrils
  • Tendrils absent
Venation
  • Pinnate
Petiole (leaf stem) Blade Ratio
  • Petiole < 25% total length
  • Petiole 25% - 75% total length
Leaf Length (blade PLUS petiole)
  • 1 - 2 cm (.40 - .80 inch)
  • 2 - 4 cm (.80 - 1.60 inches)
  • 4 - 10 cm (1.60 - 4.0 inches)
Leaf Width
  • 1 - 2 cm (.40 - .80 inch)
  • 2 - 4 cm (.80 - 1.6 inches)
Leaf or Leaflet Margin
  • Serrate
Leaf or Leaflet Blade Base
  • Acute (cuneate)
Leaf or Leaflet Tip
  • Acuminate (attenuate)
  • Aristate
Leaf or Leaflet Blade Surface
  • Glabrous (NO hairs)
  • Sparsely hairy
  • 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)
  • 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)
  • 8 - 10 dm (2.6 - 3.3 feet)
Wind Dissemination
  • Not wind disseminated
Moisture Regime
  • Mesic
Chlorophyll
  • Present

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

Root or Vegetative Propagule
  • Tap Root

US State
  • Alabama
  • Arkansas
  • Connecticut
  • Delaware
  • Florida
  • Georgia
  • Illinois
  • Kansas
  • Kentucky
  • Louisiana
  • Massachusetts
  • Maine
  • Michigan
  • Missouri
  • Mississippi
  • North Carolina
  • New Hampshire
  • New Jersey
  • New York
  • Ohio
  • Pennsylvania
  • South Carolina
  • Tennessee
  • Texas
  • Virginia
  • Wisconsin
  • West Virginia
  • Hawaii
  • Indiana
  • Maryland
  • Rhode Island
  • Vermont
  • Alaska
  • Arizona
  • California
  • Colorado
  • Iowa
  • Idaho
  • Minnesota
  • Montana
  • North Dakota
  • New Mexico
  • Nevada
  • Oklahoma
  • Oregon
  • South Dakota
  • Utah
  • Washington
  • Wyoming
  • Nebraska
Canadian Province or Territory
  • British Columbia
  • New Brunswick
  • Nova Scotia
  • Ontario
  • Prince Edward Island
  • Quebec
  • Alberta
  • Manitoba
  • Newfoundland
  • Saskatchewan
  • Yukon
  • Northwest Territory
Other
  • Puerto Rico
  • Virgin Islands
  • District of Columbia
  • Labrador

  • An Illustrated Guide To Arizona Weeds, 1972 (ISBN 0-8165-0288-9) 338 pages. See page: 174
  • Common Weeds of the Canadian Prairies, 1963 (Cat# A53-1136-1) See page: 49
  • Field Guide To The Common Weeds Of Kansas, 1983 (ISBN 0-7006-0233-X) See page: 62
  • Identification Guide to the Weeds of Quebec, 1999 (ISBN# 2-89457-174-7) See page: 213
  • Northwest Weeds, 1990 (ISBN 0-87842-249-8) See page: 67
  • Weed Seeds of the Great Plains, 1993 University of Kansas# 92-125-B ISBN# 0-7006-0651-3 See index #: 100
  • Weeds, 1955 (1980) Walter Conrad Muenscher, ISBN# 0-8014-1266-8 See page: 285
  • Weeds of California, 1970, State of California Publications and Documents. See page: 263
  • Weeds of California and other Western States, 2007 (ISBN 13: 978-1-879906-69-3) See Page: 780
  • Weeds of the Northern United States and Canada, 1964 Montgomery See page: 101
  • Weeds of the Northern U.S, and Canada, 1999 Royer and Dickinson, (ISBN# 1-55105-221-0) See page: 307 - 309
  • 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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