Home Grazing Gear Up For Grazing Contents Tame Thistles

Sustainable Farming Connection
Where farmers find and share information.

Tame Thistles
Low-cost weed-control strategies that work wonders.

Graziers around the country agree: Sound grazing management can go along way toward forcing noxious weeds out of pastures, making more room for productive grasses and legumes. But with some weeds, that may not be enough. Judging from discussions on the graze-l internet listserver, thistles top of the list of persistent problem weeds that require vigilance, persistence and a few tricks to rein in. Fortunately, early fall is one of the best times to tame thistles. So you still have a chance this season to take some of the sting out of these unwelcome invaders, and have cleaner pastures next year.

Thistles are at their worst in mismanaged or newly established pastures. "Thistles and burdocks have been a common problem wherever I've worked developing new pastures or improving old, overgrazed ones," observes Tom Cadwallader, a University of Wisconsin Extension Livestock Agent based in Merrill, Wis. "I've used clipping, shovels, and a variety of herbicides," he adds. "Regular spot treatment with any of these will cut off the majority of growth during the first couple of years -- if the pasture is being managed to promote strong competitive grass and legume growth."

Here are some key strategies to consider:

Know your opponent. Canada thistle is the toughest member of the family. This perennial multiplies both by seed and spreading horizontal roots called rhizomes. Most other thistles, such as bull and musk thistles, are biennials. Their first year, they produce 4- to 18-inch-wide rosettes, but must first go through a cold winter period before they flower, set seed and die the following season. Unlike Canada thistle, these biennials can be knocked out by keeping them from setting seed. On suitable ground, rotating to annual crops for a year or two will usually wipe them out because they can't take the combination of tillage and crop competition.

Use an ounce of prevention. Thistles are opportunists, just waiting for a chance to sneak into open spots in your pasture sward. So keep your sod thick and healthy by not overgrazing and ensuring adequate fertility and lime, and you can shut out thistles before they get a foothold.

"I can't emphasize enough that the best weed control -- including for thistles -- is a dense, vigorous, rapidly growing perennial sod that fully covers the soil," stresses Dr. Ann Clark, a grazier and agronomist at the University of Guelph in Ontario. "I do not doubt that that is one reason why thistles just about disappear in most parts of our pastures." To ensure a healthy sod, Clark carefully manages grazing, fertilizes annually based on soil tests, and topclips pastures once each season.

Thistles can become especially thick under permanent wires where stock sometimes root the ground, -- creating bare spots -- but seldom graze or trample enough to kill the thistles. Clip weeds in fence lines a couple of times a year before they go to seed. Also avoid inadvertently bringing seed into uninfested pastures on implements and animals or in weed-seed contaminated manure.

Call out the `thistle patrol.' Make a habit of carrying (and using) a hoe, shovel, knife or bottle of herbicide, and chopping, digging, hacking or squirting thistles every time you see them. Your persistence will pay off.

"I've been told by experienced graziers that cutting thistle is most effective later in the season, when the core is hollow and reproduction is underway," relays Clark. "When cut young, they say the thistles just regrow. But I've always just hacked them off whenever I see them. After a few years, they pretty well disappear, except near the fencelines."

If the plant has gone to flower, do not just cut it off at the soil and leave it on the ground, she cautions. "The flowers will continue to develop and seed will fly. I cut off the developed heads when I find such a plant, and burn or dispose of them elsewhere. As with quackgrass rhizomes, you must even be careful where you spread the ashes," Clark jokes.

Dave Gneiser, Berlin, Wis., suggests generously sprinkling some salt on the thistle stump that remains after cutting to prevent regrowth, then using old twine and diesel fuel to get the thistles' funeral pyre going. "I highly recommend thistle patrol be delegated to farmers' children," he suggests. "Mine also pull mustard (yellow rocket) and are compensated by the piece rate."

Spot spray 'em. "I opt to do occasional spot spraying," says Cadwallader. "With the vast acres of golf courses and lawns in our area, I don't think that the 1 or 2 liters of herbicide that I might judiciously use each year on my 150 acre farm will cause any environmental disasters. Besides, I consider it therapy, because I usually imagine someone's face painted on the plant. Some people use punching bags, I zap thistles," he quips.

2,4-D is widely used for thistle control, but one application is seldom enough to kill the plants. This systemic herbicide usually will not kill or severely injure nearby forage legumes. Overapplication may reduce 2,4-D's effectiveness by killing the tops before much of the active ingredient moves to the roots.

A University of Wisconsin study showed that 2,4-D works best when thistles are in the rosette stage, usually in early May or again in mid-September in most of the Dairy Belt. A rate of 1 pound of active ingredient per acre was sufficient to kill virtually all of the plumeless thistles at that stage. But once they started to bolt, a mix of .75 pounds of 2,4-D and .25 pounds of Banvel worked better.

Banvel at rates of 2 to 4 quarts per acre will produce a near-total kill on actively growing thistles, but these high rates may also kill forage legumes, and stunt grasses temporarily. Roundup doesn't work very well on deep-rooted crops and will also kill surrounding forages, notes Cadwallader. But both Roundup and Banvel can be wick-applied when thistles are a foot or so taller than surrounding forages. In another Wisconsin study, two passes of Roundup with a rope wick only partially killed Bull thistles, but stopped their flowering totally.

Be sure to allow at least two or three hours between application and rain to avoid having the chemicals wash off the plants before they have a chance to take them up. Apply all herbicides following label recommendations. Check with local Extension or ag chemical dealers for more details.

Hit them when they're weak. Perhaps the best time to spray thistles is in the early fall, when temperatures are still in the 70s F. Nearly all of the plants will be in the rosette stage and actively growing. At this point in the season, the thistles are transporting sugars and starches to their roots for winter, and so more effectively carry the herbicide down along with these nutrients than in spring. Harsh winter weather will likely finish off most of the thistles that the herbicide doesn't kill outright.

Enlist `kids.' Sheep and cows may nibble at young thistles up to 8 inches tall. But goats relish them, especially the blossoms, virtually eliminating production of new seed. "No grazier should be grazing cattle without goats as companions," says Charles Reed, Linn Creek, Mo. "There is no other enterprise that will control weeds and brush, improve the quality of the pasture, and give you a paycheck to boot." Reed has found that he can run two or more goats with each cow and generate an additional $150 or more in income with about $50 in added expenses.

While no one wants thistles in their pastures, keep in mind that not all weeds are necessarily evil incarnate. Dandelions and dock, for example, can pack as much protein as alfalfa, and can help fill in around more desirable species while pastures mature. "Last summer I had a wonderful stand of a plant we call white cockle show up in a pasture that was only a couple of years old," relates Cadwallader. "The grasses were still a bit thin, and I had lost some clover in a few spots so the cockle had very little competition.

"My 75-year-old neighbor drove in the yard visibly upset and asked me what I was going to do about my beautiful white-cockle stand. He grew up in the days when the kids were sent out to pull weeds. I think he was expecting me to be ashamed, since I'm a county agent. But when I said I wasn't going to do anything, I think you could have knocked him over with a feather.

"I took him to the pasture where I had just turned in the sheep to show him why I wasn't concerned," Cadwallader continues. "The first thing they had eaten was the cockle flower itself, and then they went on to the rest of the plant. To me as a shepherd, I didn't see the cockle as a weed, but as a forage. My poor neighbor didn't know what to say. He just shook his head and went home.

"This year the sod is stronger, and the cockles are about gone."

Let Weeds Take Care of Themselves!
Being trained in traditional agronomy, I tend to immediately think of weed control in terms of direct chemical or mechanical action. But since becoming involved with management-intensive grazing, and more recently Holistic Resource Management (HRM), I now take a broader and longer-term view.

Weed control on my land is no longer primarily by chemical or mechanical means, but by livestock impact. Yes, I still mow some, but mostly to maintain correct grass maturity. And I also own a sulky-type weed-wiper, but am considering converting it to a cart for my Newfoundland dog to pull in parades.

In '94, most of the land that is now my 50 acres of pasture was abandoned vegetable ground with a pH of 5.2. Twenty acres hadn't seen a crop in years and was completely overrun with goldenrod, blackberries, wild strawberries and some native grasses. Ten acres had been recently fallowed, and another 20 was in grass hay.

In late '94, I disked some of the fallow area to smooth it up, and planted 5 acres of winter rye. I also did some liming, but University of Vermont pasture specialist Bill Murphy suggests that I might not have even needed that expense. Then in Feb. '95, I frost-seeded 10 acres with orchardgrass and white clover. While '95 was the driest growing season on record, that 50 acres supported 60 stockers for more than four months. The fallow land grew into orchardgrass, quackgrass, white- and red clover, and other miscellaneous species including some weeds. The abandoned weedy area grew into orchardgrass, some quackgrass, clovers, and native grasses, though it still has some goldenrod and wild strawberries. Fortunately, the blackberries are very sensitive to mowing. The long term hay area is still mostly timothy with some clovers coming in, though I'm most disappointed with the speed of its change.

This year ('96), there is still a fair amount of bare soil and some goldenrod and thistle out there. I don't like them. But until the bare areas fill in with more desirable plants, I can see little point in not letting the weeds exist. They may not be attractive, but they also aren't causing any harm. If I manage the cattle grazing well -- which includes some mowing to manage grass maturity -- the pasture will continue to convert to what I want. Though it still has a lot of improvement to go, I expect it to compare favorably with almost any other pasture in five years. But my cost of developing a quality forage stand will be mostly management -- not cash.

To me, weeds are a symptom of a problem -- not the cause. By managing cattle for the plant species I want, the symptoms are going away quite rapidly. When the pasture is higher quality, I may have less patience with weeds. But today I am tolerant due to the progress I'm making, and I don't care to invest more money or mental energy in eliminate them completely.

Nathan R. Leonard
Area Extension Specialist
Cortland, N.Y.

Top of Page

Home Grazing Gear Up For Grazing Contents Tame Thistles

©1997 Committee for Sustainable Farm Publishing

Please read about our usage permission policy and disclaimer.

Send comments, suggestions and questions to the site author:
Craig Cramer cdcramer@clarityconnect.com

Coded using HoTMetaL Pro 3.0. Best viewed in Netscape 3.0 or later.
Please see our credits page for more information.