Tips for identifying fall emerging weeds
Shepherd’s-purse is a winter annual (rarely biennial) mostly found in cultivated areas, fields, lawns, gardens and roadsides. The seeds of shepherd’s purse need cold temperatures to break dormancy and germinate when the soil temperature goes below 60°F.
Flowering period: March- November
Distinguishing features: The leaves are alternate, forming a basal rosette. They are pinnately lobed and smaller apically. The flower stalks (called raceme) are unbranched to slightly branched. The plant will be 6 to 18 inches tall and bear white flowers. The fruits of shepherd’s purse are triangular- or heart-shaped.
Seedling characteristics: Cotyledons are round or spatulate in shape and may be slightly indented at the tip.
Tansymustard is a winter annual that can be found in rangeland, roadsides, and fields. It contains toxic levels of nitrate and is harmful for cattle to consume.
Flowering period: March-August
Distinguishing features: The leaves are segmented in a narrow pattern. Plants are 0.3 to 2.9 feet tall with simple or branched stems. Flowers are bright yellow and fruits (called silique) are club-shaped similar to mustard fruits.
Seedling characteristics: Seedlings are reddish green to purple.
Prickly lettuce is a common winter annual found throughout the Great Plains in disturbed habitats, roadsides, gardens, pastures, and cultivated fields. It causes pulmonary emphysema in cattle when consumed in large quantity.
Flowering period: July-September
Distinguishing features: Leaves are alternate and deeply dentate. Middle to lower leaves have stiff bristles along the bottom mid-rib. Stems contain a substance that looks like white latex. Each flower head contains up to 25 yellow flowers. Each flower looks like a small dandelion flower.
Seedling characteristics: Seedlings exist as a basal rosette until flowering stems develop.
Several herbicides have been registered for control of fall emerging weeds. The CropWatch article Managing Winter Annual Weeds Starts this Fall” provides good information for fall weed management. For more details about herbicide options for fall emerging weeds, see pages 59 and 103 in the 2013 Guide for Weed Management in Nebraska, EC 130. (The 2014 edition will be released in early January.)
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