Can Horses Eat Johnson Grass? Safety Tips & Risks Explained

The scent of fresh-cut grass wafting through the barnyard is enough to make any horse prick up its ears in anticipation. But not all that’s green is good—especially when it comes to Johnson grass. If you’ve spotted this tall, feathery plant creeping into your pastures, you might be wondering: can horses eat Johnson grass safely? The short answer is no, not without serious risks. This invasive grass hides a dangerous secret: under stress, it produces cyanide, a toxin that can be fatal to horses in small doses. Yet, with the right precautions, you can manage its presence and keep your herd safe. Let’s dig deeper.

Why Johnson Grass Is Dangerous for Horses

Johnson grass (Sorghum halepense) might look harmless swaying in the breeze, but it’s a master of disguise. When drought, frost, or herbicide stress hits, the plant releases cyanogenic glycosides, which convert to prussic acid (hydrogen cyanide) when chewed. For horses, even a few pounds of contaminated forage can lead to respiratory failure, seizures, or death within hours. Symptoms of poisoning include:

• Bright red mucous membranes (gums, nostrils)
• Labored breathing or gasping
• Staggering or collapse
• Excessive drooling

Young, rapidly growing Johnson grass is the riskiest, but wilted cuttings or baled hay containing the plant are equally hazardous. And let’s be honest—horses aren’t picky when it comes to grazing. If it’s green, they’ll likely nibble.

Safety Tips If Johnson Grass Is Nearby

Eradicating Johnson grass entirely is tough (it’s nicknamed "the cockroach of weeds" for a reason), but you can minimize risks:

1. Test Your Pastures

Before panic sets in, confirm the plant’s identity. Johnson grass has broad leaves with a prominent white midrib and grows in dense clumps up to 8 feet tall. Purple-tinged seed heads appear in late summer. If unsure, consult your local agricultural extension office.

2. Control Growth Strategically

Mowing alone won’t kill Johnson grass—it’ll just laugh and regrow. Instead:

• Herbicides: Use glyphosate or quinclorac in early growth stages, but keep horses off treated areas for at least 2 weeks.
• Grazing rotation: Restrict access to infested fields, especially during droughts or after frost.
• Soil health: Improve drainage and fertility; Johnson grass thrives in compacted, nutrient-poor soil.

3. Monitor Hay Sources

Hay contaminated with Johnson grass is a silent threat. Ask suppliers for a weed-free guarantee, and inspect bales for telltale seed heads or stems. When in doubt, skip it—better safe than sorry.

What If Your Horse Eats Johnson Grass?

Time is critical. If you suspect ingestion:

• Remove all access to the plant immediately.
• Call your vet—even if symptoms seem mild. Cyanide poisoning progresses rapidly.
• Offer fresh water to help dilute toxins (but don’t force it if the horse is distressed).

Vets may administer sodium thiosulfate intravenously, an antidote that binds cyanide. Recovery depends on the dose consumed, but prompt action saves lives.

Safe Alternatives for Grazing

Replace Johnson grass with horse-friendly forage like:

• Timothy grass: High fiber, low sugar.
• Bermudagrass: Drought-resistant and palatable.
• Orchardgrass: Soft texture, ideal for sensitive teeth.

Fun fact: Horses often prefer these options anyway—they’re the gourmet buffet of the pasture world. 🌱

The Bottom Line

Johnson grass and horses are a bad mix. While a nibble here or there might not spell disaster, the stakes are too high to gamble. By staying vigilant, testing pastures, and sourcing clean hay, you can protect your herd from this deceptive danger.

There’s something profoundly peaceful about watching horses graze under a golden sunset, their tails flicking contentedly. That peace hinges on knowing every blade beneath their feet is safe. So take a walk through your fields today—your horse’s health is worth every step.