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Weed Identification Guide

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Proper weed identification is essential for determining the best method of weed control. Weed identification books are helpful but there are so many choices that selecting the proper weed may be difficult. It is easier to identify the weed to the weed family and narrow the choices. Most weed books have weeds arranged according to their family. The below key will narrow the choices making weed identification much easier.

WSU Extension also provides a weed identification service where your specimens may be identified by a professional taxonomist or weed science Extension specialist. There is no charge.


Weed Identification Quick Guide

  • Horsetails: The plant is leafless, with a straight, finely-ridged stem with joints at regular intervals without flowers.
  • Ferns: The stems are not jointed or hollow, leaves large and pinnately dissected, nonflowering.
  • Grasses: The stems are cylindrical and hollow, leaves are slender with parallel veins.
  • Sedges: The stems are triangular and solid, leaves in three rows.
  • Rushes: The stems are round and solid.
  • Buckwheat family: The plant stem has a paper-like collar at the base of each leaf.
  • Pigweed, Miner’s lettuce and Lambsquarters: The plant has lens-shaped, black or dark brown, shiny seeds.
  • Pink family: The plant has opposite leaves that appear joined around the swollen joints of the plant stem.
  • Mustard: The plant has alternate leaves and small four-part flowers in white, yellow, or purple..
  • Legume: The plant has compound leaves and flowers are typical pea blossom shape, check..
  • Parsley: The flowers are tiny and in a broad, flat cluster at the ends of the stem.
  • Spurges, Dogbanes, Milkweeds, and Sunflowers families:The plant has a milky juice.
  • Borage: The plant stem and leaves are bristly-hairy.
  • Mint: The plant has a square stem (check by rolling between thumb and finger) and leaves are opposite (paired).
  • Toadflax: The plant flowers resemble those of snapdragons.
  • Bedstraw: The plant has a square stem, tiny, white, four-part flowers, and leaves are in whorls (circles) around the plant stem.
  • Corn spurry: The plant has a round stem and leaves appear to be in whorls (circles) around the plant stem.
  • Sunflower: The plant has a flower head with many small tube-like flowers clustered on a common base, with an outer row of strap-shaped flowers in some species.
  • Nightshade: The flower has five star-petals resembling a tomato flower, usually yellow, white or blue, and the fruit is a berry or spiny capsule.

Updated 02/07/10

Washington State University