EarthSky // Blogs // Food Posted Oct 27, 2008

Sheep: The new weapon against invasive plants

Photo Credit: Julie_Berlin
Photo Credit: Julie_Berlin

What’s better than spraying herbicides on a field full of non-native weeds? Setting a herd of sheep loose on it to chow down. That’s what they’re doing in Missoula, Montana, where 1,000 acres of public lands above the Missoula Valley have been invaded by non-native weeds such as leafy spurge and knapweed. The sheep feast…read more »

What’s better than spraying herbicides on a field full of non-native weeds? Setting a herd of sheep loose on it to chow down.

That’s what they’re doing in Missoula, Montana, where 1,000 acres of public lands above the Missoula Valley have been invaded by non-native weeds such as leafy spurge and knapweed.

The sheep feast on the weeds all summer and part of the fall, then are rounded up and chased home to a local ranch before the winter snows begin. The New York Times featured a story about these sheep yesterday.

I’ve heard of people using goats to keep their lawns cropped, but I’ve never seen sheep employed in a plant management role. Apparently grazing sheep for weed control has also caught on at Civil War battlefields and ski slopes, among other places.

I love the idea! As the article mentions, sheep are a low-cost, non-toxic way to get rid of weeds. Much better than spraying loads of herbicides. Plus they provide a bucolic look — and allow sheep farmers to get a return on their investment (or in this case, allow a rancher to afford to keep his ranch).

One plant ecologist at the University of Montana, however, notes that there’s no data to show whether they sheep are having a positive or negative impact on the environment. They could be causing erosion and moving invasive weed seeds to new places.

It’s probably worth studying these sheep more, but call me a romantic — I prefer the sheep weed-eating strategy to spraying 1,000 acres with herbicide.

What do you think? Post your comments here!

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3 Responses to Sheep: The new weapon against invasive plants

  1. Jennifer Leaf says:

    They could heighten the weed control by adding a few goats to the flock of sheep. The two species prefer different plants; sheep will nip grass (and some broad leaved plants) right down to the ground while goats tend to browse and prune off the growing tips of broad leaved plants (and shrubs and trees), which can delay or even prevent a plant from setting seed if the animals are kept in the area until fall. Both should be used judiciously however, because of the risk of overgrazing. I would not recommend them on an extended basis for very steep or riparian areas due to the risk of overgrazing and negative impact.

  2. Benjamin Napier says:

    Jennnifer is correct. Managing the grazing of sheep is very important. The reason for many a range war in the Old West was becasue sheep herders allowed the sheep to absolutely wipe out the grazing land. Also, cattle don’t like to brouse where sheep have been recently.

    Cattle, sheep and goats are all good tools to manage pasture land. They are the best way known to convert pow quality plant protein into high quality protein for humnans. Judicious use of grazing is important to prevent the destruction of perrenial planlife, though. Also, if grazing is allow to be too heavy prior to seed drop, annual plants will be eradicated as well.

    Chickens and geese can be used to weed gardens as well.

  3. futuRich says:

    Thats cool, and sounds a lot more eco-friendly to do it this way. I guess it’s only plausible if you can manage taking car of all those sheep.

  4. Glenn Hoffman says:

    Employing sheep to control the visible aspect of plant management is great idea. There are obvious limitations where this can be done, but assuming you don’t have neighbors that object, its ideal for the environment and the land owner. However, not sure the sheep would contain the invasive plants.