Drought -- When Weeds Can Become Friends

Drought in Mercer County, 2017. Photo by NDSU

Weeds can be beneficial in the right place or situation.

July 2017

Richard Zollinger, Weed Specialist

Weeds generally are despised by everyone who has to deal with them. Weeds compete with crops, use valuable water and nutrients, interfere with crop harvest, harbor insects and diseases, poison livestock and humans, and are aesthetically unappealing. However, weeds also may have beneficial qualities in the right place or situation. A weed can be defined as a plant out of place, a plant growing where it is not desired, or a plant whose virtues have yet to be discovered. Weeds may have some virtues in dry years when growth and production of more desirable plants is limited.

Kochia and Russian thistle can be used as an alternative livestock feed if more desirable pasture or feed is limiting. Although the nutritional quality of these plants is less than alfalfa, they can be used to supplement feed rations. Livestock do not grow as well when fed these plants as they do when fed other forage crops. Kochia and Russian thistle should be used as feed only when quality forages are not available.

Russian thistle and kochia are most palatable if harvested prior to flowering. Russian thistle is best utilized by grazing or as hay. It does not make good silage because of a high water content and disagreeable odor. Kochia makes good pasture, hay, or silage. Russian thistle and kochia may have laxative and other adverse effects if fed exclusively, and thus should be fed in combination with other feeds such as straw or grass hay. As with most plants, kochia and Russian thistle may accumulate high nitrate levels during hot, dry conditions. A nitrate test should be conducted prior to using the feed.

Another situation where weeds may prove beneficial is as ground cover on fallow or stubble fields over the winter. This is especially true in dry years when limited plant residues are on the soil surface, the soil is dry and loose, and the fields are extremely vulnerable to erosion. However, management is very important to prevent excessive growth and weed seed production. Weeds allowed to grow to maturity will use valuable moisture and nutrients, as well as produce seeds for future reinfestations.

Weeds that germinate and emerge after September 1 probably will not become mature and produce viable seeds prior to the first killing frost. A herbicide treatment such as Roundup, Landmaster BW, Fallow Master or Gramoxone Extra may be needed to suppress weed growth if weeds emerged earlier in the summer. Clipping or mowing is also an option for control of weeds and minimizing seed production.

Not all weeds make a good ground cover. Kochia and Russian thistle are examples of tumble weeds. Tumble weeds break off at the base of the stem during winter and roll across the fields spreading seed as they go. Subsequently, they often become entangled in fences and are a nuisance to remove. Therefore, these weeds would not be desirable as a "cover crop." However, foxtail or pigeongrass can be good ground cover because of their fibrous root system. Winter annual weeds that remain alive over winter also can make good ground cover but would need to be controlled early in the spring before they bolt and the flowering stem begins to elongate. Winter annual weeds become much more tolerant to herbicides and more difficult to kill once they begin to bolt.

Additional Reading

BeefTalk: A Beef Cow is What She Eats

NDSU North Dakota Weed Control Guide