A John Deere Publication

aerial photo of bare trees surrounded by yellow prairie grassland

Left unchecked, trees can quickly overwhelm native grass pastures, reducing productivity. Below. Mechanical removal of trees, followed by herbicide treatment of hardwood stumps, is often necessary.

Sustainability, Education April 01, 2023

Scourge of the Prairie

Control of the Eastern Red Cedar improves grassland and water quantity.

by Bill Spiegel

Whenever Doug Spencer sees trees encroaching grassland, road ditches, and fence lines of Kansas highways and county roads, his anxiety increases.

These trees—cedars, locust and hedge—are weeds. They damage the prairie biome, ingest gallons of groundwater per day, consume nutrients that could feed native grasses, and emit tens of thousands of seeds per tree each year.

Spencer, grazing specialist for the Kansas Natural Resources Conservation Service, says woody plants are choking out the native grasses in the Great Plains region, which USDA-NRCS considers the 10 states from Montana and North Dakota south to Texas.

Since 1999, woody plants have increased on more than 108 million acres, the agency says. Grassland lost to woody encroachment is almost as great as the rate of grasslands converted to farmland, according to Spencer.

"I don't hate trees," Spencer points out. "But I don't think we understand the sort of risk they are to grasslands."

Less than two centuries ago, the Great Plains was blanketed with native plant species. Lightning strikes touched off fire, which was nature's way of keeping the prairie free from woody species. The vast Great Plains landscape was broken up by settlement with farm fields and fenced off pastures, and vast fires were prevented.

All of these contributed to the inevitability of more trees overwhelming landscapes in which they don't belong.

The ease by which weedy species proliferate is staggering. "I've seen locust trees as far as a quarter mile or half mile away from the seed source, because of animal dispersal," Spencer says.

An eastern red cedar tree becomes mature within six years and can produce more than 1.5 million seeds annually, according to the University of Nebraska. Nearly 95% of those seeds will be dispersed within 200 yards.

Moreover, a single mature eastern red cedar may guzzle 30 gallons of water per day, limiting water availability to native species.

Work to combat invasive trees is arduous, hard, and slow but is beginning to reap rewards, says Daniel Mushrush, a rancher near Elmdale, Kansas. He and his brother, Chris, are collaborating with neighbors as part of the Great Plains Grassland Initiative (GPGI) effort known as "Defend the Core, Grow the Core" to remediate woody species encroachment. Adjoining landowners collaborate to control outlying trees first, then tackle denser infestations. Participants are cutting trees, then treating cut stumps with herbicides to prevent regrowth. In coming years, the area will receive prescribed burns.

"This is the last of the tallgrass prairie and is a unique biome," Daniel says. "We've let it slip with some of these woody species but when managed correctly, there's a lot of synergy."

Already, Mushrush sees progress: a contractor removed a dense thicket of trees from a draw in early 2022. Last summer, he noticed it was running water for the first time in years. Cleared areas aren't immediately recovering to dense grass, but Spencer says grass will come back with time.

Hard work now will spare future generations from a similar effort, the Mushrushes anticipate.

"We're 30 years behind. This got ahead of us before we realized," Daniel notes. "If we keep them beat down, it isn't the massive problem we've let it become." ‡

two men standing in dry brown prairie and decaying crumbling trees

Above. Mechanical removal of trees, followed by herbicide treatment of hardwood stumps, is often necessary. Brothers Chris and Daniel Mushrush are part of a Kansas effort to stop the encroachment of woody species.