Jingjing Yin, Commercial Ornamental Horticulture Specialist
Cornell Cooperative Extension
Capital Area Agriculture and Horticulture Program
Common lambsquarters (Chenopodium album L.) is a broadleaf summer annual. It is one member of the goosefoot family. It was once thought to be a native of Europe and Asia. However, recent archaeological studies show that the seeds were stored and used by the American Blackfoot Indians during the sixteenth century. In prehistoric times, the seeds of common labsquarters were harvested, dried, and ground to make flour for human consumption. Many members of the goosefoot family are edible vegetables. The plant is eaten readily by livestock when it is young, but it becomes woody and unpalatable with age.
Common labmsquarters is found in many agricultural and horticultural systems throughout most of the U.S. It is competitive with more than 40 crop species worldwide and is considered a principal weed for corn and soybean producers in the U.S. It is also a host for several crop diseases such as cucumber mosaic virus, bean yellow mosaic virus, potato virus, soybean mosaic virus, etc. However, it is notorious for its resistance to multiple types of herbicides, including photosystem II inhibitors (triazines), ALSinhibitors, and glyphosate.
Common lambsquarter seedlings emerge in the spring to early summer. Cotyledons are distinctively long and narrow, with no midvein and purple undersides. While the first pair of leaves to emerge are opposite each other, all subsequent leaves are alternately arranged. On the surfaces of cotyledons, young leaves, and stems, there is a grayish-white powdery coating. Adult lambsquarter plants can grow up to 3 feet tall. Leaves on adult plants are alternate and irregularly toothed. Freshly emerging leaves have the same grayish-white powdery coating as the seedlings. Flowers are produced from June to September. Tiny, green, stalkless flowers are packed in dense clusters at the tips of the main stem and branches. Late emerging plants can begin to set seed within six weeks, even on very small plants. One lambsquarter plant can produce up to 72,000 seeds.
Tillage and cultivation can promote germination and that peak emergence often occurs within 2 to 3 weeks of turning the soil. The optimum seed depth for emergence is about 0.1 inch, and very few seedlings emerge from deeper than 1 inch. Deeper tillage will bring seeds to the near-surface zone which is favorable for germination.
The best control method is to prevent infestation and spreading by minimizing seed production. Common lambsquaters cannot recover from uprooting or mechanical damage. Tillage timed to correspond with peak emergence with repeated surface cultivation can be effective to reduce the number of plants and results in fewer seeds. Mowing is another way to prevent seed production. Once the crops are large enough to tolerate inter-row cultivation, hilling up slightly when the lambsquarter seedlings are still in the early seed-leaf stage can bury the tiny seedlings. A thick layer of straw mulch and other mulch materials will suppress common lambsquarter seeds from germination as well. Fall clean up after harvest can reduce lambsquarters density in the following year. If possible, remove plants that have flowered. Hand rogue at least the larger plants out of intensive vegetable systems.
Common lambsquarters is highly responsive to N fertility. Avoid excess fertilization especially avoid heavy fertilization before the crops are well established. Incorporation of a legume cover crop can enhance seedbank decline of this weed by triggering fatal germination of buried seeds.
Preemergence herbicides can effectively control common lambsquarters in corn and soybean, and there are a number of effective postemergence herbicides available in corn. Postemergence control in soybean can be more difficult. Some common lambsquarters populations can germinate later in the growing season or are triazine-resistant, so they require a combination of preemergence and postemergence herbicides for effective control. For herbicide options, contact your local cooperative extension.
References:
Curran B., Sprague C., Stachler J., and Loux M. 2007. Biology and management of common lambsquarters. The Glyphosate, Weeds, and Crops Series. Purdue Extension.
Common Lambsquarters. Cornell Weed Profiles: https://cals.cornell.edu/weed-science/weed-profiles/common-lambsquarters
Common Lambsquarters. Pennsylvania State University, College of Agriculture, Cooperative Extension Service: https://www.maine.gov/dacf/php/gotpests/weeds/factsheets/lambsquarters-penn.pdf