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How To Control Weeds And Johnson Grass In A Horse Pasture

It’s important to keep Johnson grass and weeds out of your horse pasture because many unwanted plants are toxic, and they take up space that could far better be used for nourishing, healthy forage. In this article, we’ll discuss some of the worst weeds found in a horse pasture setting and provide good tips on identifying them and eliminating them. Read on to learn more about the best way to get rid of weeds in a hay field and how to get rid of Johnson grass in hay field.

Weeds To Watch Out For

how to get rid of johnsongrass in hay field

It’s always wise to familiarize yourself with the wild plants that are native or naturalized to your area. Learn which ones are poisonous and which are not.

Take special care to remove these poisonous weeds if they should pop up in your pasture:

1. Russian knapweed is highly toxic to horses. This plant is a vigorous grower that will quickly take over your pasture if it has bare ground where it can take root. The seeds are blown about freely and are very opportunistic. Knapweed not only crowds out other plants, but it also secretes chemicals that contaminate the soil and kills other plants. Before you know it you’ll have a field full of knapweed and nothing else.

2. Poison hemlock is a tall plant with many stems that likes to grow in wet, shady areas throughout the US. It looks quite a bit like Queen Anne’s lace which is not poisonous, but look closely. If the plant has a red, purple or splotchy purple stem, it is poison hemlock. The plant has many neurotoxins that can cause lack of coordination, tremors and respiratory failure. If you see any poison hemlock, pull it by hand immediately and get rid of it very carefully. Frequent mowing will eventually kill this plant.

3. Water hemlock is often found growing in wet areas and along the sides of streams. Like all hemlock it is quite poisonous. It only takes one or two ounces of this highly poisonous plant to kill a horse. It is actually more poisonous than poison hemlock. Watch for it early in the spring. When you remove it, be sure to kill both the foliage and the root, which is quite poisonous.

4. Houndstongue is a non-native, invasive weed that can spread through your pasture very quickly. This weed is toxic both fresh and dried, so it’s important that you remove it as soon as you treat it or cut it down. Search through your hay to make sure you do not have dried houndstongue lurking there.

5. Groundsel (aka: golden or yellow ragwort, or butterweed) may cause photosensitization and/or liver disease. It is a pretty little wildflower with small, yellow, daisy like blossoms that are filled with pyrrolizidine alkatoids.

6. Narrow leafed milkweed is quite toxic, but broadleaf is not. Learn to identify one from the other.

7. Buttercups have a bitter taste that usually keeps horses from eating them. Horses on poor pasture may resort to them, though. When this happens, diarrhea, colic and drooling will result.

8. White snakeroot is a toxic woodland plant found in shady places. The toxic effects are not immediate, but a horse who has eaten this tall, upright plant with clusters of white flowers will die within a couple of days.

9. Hemp dogbane contains a poisonous milky sap. It’s leaves are small and soft, and it may be attractive to some horses. You can keep this poisonous weed under control through herbicides and mowing.

10. Hoary alyssum is a drought loving weed that can take your pasture over during dry spells. This plant is very poisonous to horses and will cause your horse to appear to be depressed. It may also cause your horse’s lower legs to swell. Colic and founder may also be caused by ingesting this weed. It’s very important to remove this weed from your pasture and also to learn to recognize it because it can look like alfalfa in its dried state. If even a bit of it sneaks into your hay, your horse will be in trouble.

11. Black walnut trees are undesirable in or around a pasture. Whether from ingestion of the leaves or standing on the roots, these trees are often associated with cases of founder. They contain a toxic chemical called juglone, which is not only dangerous to horses, it also kills all vegetation surrounding the tree. If there is one near your pasture, be sure to check for and remove fallen branches on the ground after high winds.

12. Johnson grass is a Mediterranean grass that was mistakenly brought to the US as a source of fodder in the early 1800s. A little bit of Johnson grass every once in a while won’t hurt your horse, but a steady diet of it (even in small amounts) eventually results in spinal cord nerve damage. Good pasture maintenance that includes regular mowing and overseeding with desirable grass seed is the best way to keep it under control. It is fairly impossible to get rid of it altogether.

Learn to identify these weeds at all phases of their lives. Even though some of them are not as poisonous when young as when mature, they are also easier to remove when they’re young. When you see a poisonous weed in your pasture, it’s important to remove it entirely. Pull it up by the roots to prevent ingestion and to prevent further growth.

Be sure to dispose of all removed weeds promptly and carefully. Put them in a sealed bag with the trash or toss them in the burn pile to be sure of eliminating their presence on your property.

Are All Weeds Toxic?

are all weeds toxic

There are a number of other weeds that take up space in your pasture and consume resources that could better be used for more nourishing grasses. Among these are:

  • Nimblewill is a native grass that looks quite a bit like Bermuda; however, horses will not eat it. It takes up space and resources in your pasture and should be kept under control. Mowing early in the season before it goes to seed is the best way to prevent its spread. Be advised, it will never be gone. You’ll need to keep a close eye and take aggressive control measures against it.
  • Thistles are related to sunflowers. They are sort of pretty, and they’re not poisonous but they can take over your pasture very quickly because they spread their seeds like dandelions. Additionally their roots are very deep and they can spread from one place to another via runners. Kill off thistles using herbicides.
  • Cockleburs and foxtails will not poison your horse, but they can injure him or her because they bear sharp seed heads and burrs that can cause damage to the mouth or simply become entangled in manes and tails.
  • Spiny amaranth or pig weed springs up in bare, compacted soil and is often seen around watering stations. It’s not poisonous, but you should mow it or pull it if you can it’s unsightly and has sharp spines at the base of its leaves that could be harmful to horses.
  • Ragweed will spring up and take your pasture over in hot dry times if it has half a chance. Horses will eat it, and this plant is not poisonous; however, if they eat too much of it or eat it over a long period of time it can cause a harmful accumulation of nitrites in your horses body. When you see ragweed, mow it when it is small or pull it when it gets larger.

Pasture Weeds: Most Toxic To Horses

Best Way To Get Rid Of Weeds In A Hay Field

One of the best ways to keep weeds out of your pasture is to prevent overgrazing. If you have too many horses and too little space, or if you simply don’t manage your pasture well and don’t rotate your horses from one grazing area to another, overgrazing is inevitable. When good grass is grazed down to the dirt, weeds and Johnson grass will happily take over and you can soon have a big problem.

Get started on a good pasture management plan by getting to know your county agent. He or she can conduct a review of your pasture and help you identify dangerous weeds.

If your pasture is absolutely overrun with weeds, you may have to kill off the entire pasture using an herbicide or controlled burn to get rid of everything that’s there and start new with a good mixture of healthy grass seed. Discuss your options with your county agent.

When you kill off undesirable weeds and Johnson grass, be sure to remove all of the dead foliage right away. It’s best if you can till your pasture and then immediately sow some good pasture grass to take the place of the weeds. Bare ground is an open invitation to weed seed.

Are Herbicides Safe For Horses?

are herbicides safe for horses

Avoid using herbicides if you can, but if you must use herbicides or weed killers be sure to discuss it with your county agent to choose the right product to deal with the weeds you have. Your county agent can also tell you about any local ordinances that may govern your use of these chemicals. And be sure to read and follow all instructions closely.

Remember that you must keep your horses out of the pasture for the period of time recommended by the manufacturer of an herbicide. Otherwise, your horses could suffer ill effects from ingesting the chemical. Be sure to remove all treated weeds from the area before allowing your horses back in.

Are There Natural Alternatives To Herbicides?

Good pasture management that strives to encourage healthy, edible, nutritious grasses will go far to discourage weed growth. Overseed your pasture with a good mix of beneficial grasses and herbs immediately after doing away with weeds.

It’s also a good idea to overseed on a regular basis as pastures get eaten down. Be sure to sow new seed on any bare patches as they appear. Keeping a good, thick, healthy stand of grass is one of the best ways to avoid weed incursion.

Encourage Beneficial Insects

natural alternatives to herbicides

Just as with gardening, partnering with beneficial insects can be a good way to manage your pasture and prevent the spread of undesirable plants. Among the beneficial insects that can help you manage your pasture, there are beetles that feed on leafy spurge, weevils that are quite fond of houndstongue and a fly that specializes in control of knapweed.

Talk with your county agent to identify native beneficial insects that may feed on the blossoms of undesirable plants. Without blooms, weeds can’t go to seed. This is a simple and effective way to prevent the spread of weeds.

Don’t Crowd Your Pasture

The importance of avoiding overgrazing cannot be stated enough. You need a minimum of 2 acres of good pasture per horse if you want your horse to get a significant amount of its nourishment from grass. Don’t overstock your pasture, and be sure to provide a good quality of free choice hay at all times. Work closely with your vet to establish just the right diet for your horse so that he will not tend to eat the grass down to the dirt, thus creating an opening for weeds to take hold.

Use pasture rotation to prevent overgrazing. Move your horses from one paddock to another when they graze the grass down to about 3 inches. Don’t allow them back into that area until the grass is about 6 inches high.

Get Help From Ruminants

get help from ruminants

When you rotate grazing, you may also wish to rotate the type of animals you have grazing. Running a small herd of sheep or goats onto your horse pasture from time to time can help keep weeds chewed down. Goats and sheep are not affected by the poisonous plants that can kill your horse.

Goats and sheep graze differently than horses. They will tend to eat all manner of plants right down to the ground. For this reason, if you use the goat or sheep method of weed control, it’s important to have enough of the animals to very quickly graze down a weedy area and then move them along so that they don’t kill off your pasture altogether.

Regular mowing can also help control weeds. Never mow your pasture lower than 4 inches, and time it so that you are mowing in a way that prevents the weeds from blooming and going to seed. Mow early in the spring before they blossom and keep an eye on them to mow again when the time comes.

Stay On Top Of Your Pasture Year-Round

You may be tempted to take a break from pasture management through the winter months when everything is apparently dead and brown, but this would be a bad idea. Be sure to keep a close eye on your pasture all year round and be vigilant about any incursion of unwanted plants and weeds. The sooner you can address these invasions, the more likely you are to succeed.

Even though horses may enjoy eating some non-toxic weeds, it’s smart to prevent this happening. For one thing, weeds do not provide the kind of nutrition and nourishment your horse needs. For another thing, when your horse eats weeds, he or she will naturally spread the weed seed in manure. Before you know it the small stand of weeds that your horse seemed to like will soon become an entire pasture full, and your horse will not be so happy.

Nicky Ellis
Nicky has been an editor at Horses & Foals since 2017. Horses have been in her life from her earliest memories, and she learned to ride a horse when she was 5. She is a mom of three who spends all her free time with her family and friends, her mare Joy, or just sipping her favorite cup of tea.


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