For Release June 26, 2005

It May Not Be a Weed

by Chuck Otte, Geary County Extension Agent

When it comes to pasture management I have a saying that goes, "Just because it isn't a grass plant, it doesn't mean it's a weed!" For whatever reason, we develop this idea that a pasture is full of grasses and anything that's not a grass is a weed. In reality, many of those forbs (what many folks would call wildflowers) in the pastures are very desirable plants that improve the overall health of the pasture and the animals that feed in that pasture.

One of the things that we quickly discovered about the Conservation Reserve Program (CRP) was that a pasture full of just warm season grasses, is a pretty poor quality pasture and it makes horrible hay. Grass is grass. It is a plant that is not prone to creating a lot of protein. Protein is created by legumes such as soybeans and alfalfa. Oh, wait a minute, many of the forbs that we see out on the pastures are actually legumes! Those legumes are selectively grazed by the cattle in that pasture and they are readily eaten if that pasture is harvested for hay.

These pasture legumes have great names such as leadplant, prairie clover (including the purple, roundheaded, silky and white varieties), catclaw sensitivebriar, partridgepea, wildindigo, and my personal favorite scurfpea. The latter is often called wild alfalfa and we are blessed with five different species of it in Kansas, two being common in the northern Flinthills. Not only do these legumes provide protein to the forage mix, they readily fix atmospheric nitrogen in the soil for the benefit of the other plants, including the grasses.

There are certainly many other forbs in our pastures that are not legumes, but may still benefit the prairie. Take western ragweed. This perennial plant looks like a short version of common ragweed. But when you pull it up, instead of getting all the root, you will simply get a short stalk attached to an underground stem called a rhizome. One plant can cover several hundred square feet. In some cases, especially droughty or overgrazed pastures, western ragweed can become very abundant and cause concern to the property owner.

The Ft. Hays Experiment station conducted some classic studies on western ragweed in the 1950s. What they found was that it took a lot of western ragweed to reduce production of the preferred native grasses. By a lot, I mean that reduction of the grass production did not occur until the amount of western ragweed exceeded 3,000 pounds per acre per year. That's a lot of ragweed!

The reason was simple; competition, or rather the lack of competition. Western ragweed is a very open foliage plant that does not shade much ground. Additionally, like many of the other perennial forbs, it has a fairly deep taproot oriented root system. The grasses have a shallower fibrous root system that actually has first shot at water. You had to get a lot of ragweed to create competition.

So why all this talk about flowers in the pastures? This is the time of year that people start to worry about all the "weeds" showing up out there. And then they start broadcast spraying entire pastures to control a problem that isn't there. If you think your pasture is being overrun by some weed, please don't immediately call in the spray rigs. Let's take some time to determine what kind of plants you have, whether they are a problem or a symptom of a problem and maybe we can handle the whole situation through better understanding and maybe a simple little change of how the pasture is managed!


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