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How to Identify Common Wheat Weeds

May 23, 2023
Weed infestation in a wheat field

Weed infestation in a wheat field

Weed infestations in wheat crops can cause severe reductions in yield by damaging the crops, out-competing for resources, or interfering with harvesting. It’s important to scout frequently and correctly identify threatening weeds to pick the right treatment program. Here are a few common weeds found in wheat fields and their key characteristics.


Kochia plant in late season wheat

Kochia plant in late season wheat

Kochia is a summer annual in the goosefoot family. Here are key features for identifying them:

  • Their height at maturity is 1’-6’ tall.
  • Kochia seedlings have cotyledons that are stalkless, elliptical and softly hairy with dull green upper surfaces and sometimes pink on the underside. Seedling stems are hairy and green to reddish in color.
  • Their stems grow upright and branched and have hairs on the upper parts. They’re sometimes tinged red.
  • Look for alternately arranged leaves with a narrow-lance shape and smooth, hairy edges. They’re typically 1-2” long and sometimes have silky hairs on the underside.
  • The flowers are small and green. They grow in clusters in the upper leaf axils and on terminal spikes.

Russian Thistle

Russian thistle plant

Russian thistle plant

Like kochia, Russian thistle is a summer annual in the goosefoot family, but their hairless leaves distinguish them from kochia. Here are other key features to look for:

  • At maturity, Russian thistle can be 0.5-4’ tall.
  • Seedling stems are striped with reddish-purple steaks. Their first true leaves appear opposite and are fleshy and needle-like.
  • Their stems are profusely branched with short, stiff hairs and reddish-purple streaks. They become stiff and dry later in the season.
  • Leaves grow alternately, and are hairless, thin and linear or needle-shaped with a stiff, prickly spine at the tip.
  • Flowers develop in the leaf axils on the upper portions of the stem and have 5 pale green to red, petal-like, membranous sepals that surround the developing seed.

Wild Oat

Wild oat plant

Wild oat plant

Wild oat is a summer annual in the grass family. One threat they pose is that their grains can mix with wheat grains, causing price penalties in harvested crops. Here is how to identify this grass:

  • Wild oat can grow up to 4’ tall.
  • Seedlings have leaves that are hairy, and the seed clings to the seedling for a long time.
  • Their stems are round and hairless.
  • Wild oat leaves are flat, rolled in the bud and often twisted counterclockwise. They can be up to 8” in length and usually have a few short hairs at the base of the blade.
  • Their flower heads are open and branched, and spikelets hang like pendants from flowering branches. They typically bloom in March-June.


Flower head of a green foxtail plant

Flower head of a green foxtail plant

Another summer annual in the grass family is foxtail. These come in yellow, green, and giant varieties and their flowers are the most distinguishing feature. Below are other features you can find:

  • Foxtails are 1-3’ tall at maturity.
  • Their seedlings’ first leaves are usually parallel to the ground and rolled in the bud.
  • Stems grow erect or bent at the base, but overall ascend upwards. They branch at the base.
  • Their leaves are 4-15” in length with a spiral twist.
  • Flower heads are spikelike, bristly and densely packed with flowers.

Wild Radish

Wild radish plant

Wild radish plant

Wild radish is a winter or summer annual in the mustard family. You can identify them by the following features:

  • They grow to 1-4’ tall.
  • Seedlings are purple with stiff hairs below their cotyledons. Seedling leaf blades are hairless and kidney shaped to heart shaped with an indent.
  • Their stems are densely hairy at the base and branched.
  • The edges of their leaves are irregularly toothed and lobed. They grow alternately, with stiff hairs on the top, bottom and edges.
  • Branched clusters of flowers grow at the ends of stem and branches. They have 4 petals each and are pale yellow to cream white with purple veins.

Common Ragweed

Common ragweed plant in a wheat field

Common ragweed plant in a wheat field

Another summer annual weed to look for is common ragweed, which is in the aster family. Here are some features to look for:

  • Common ragweed grows to 1-3’ in height.
  • Seedling stems are purple, cotyledons are dark green and paddle shaped and young leaves are green and deeply divided into lobes.
  • Their stems are branched and densely covered with rough hairs.
  • Leaves grow to 2-4” in length and are fern-like with longer stalks on lower parts of the plants.
  • Green flowers are arranged in clusters of male and female flowers.

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