Common clover species found in lawns and fields are not poisonous to humans. White clover and red clover have been eaten by communities around the world for centuries and are considered edible plants with genuine nutritional value. The real risks from clover depend on who’s eating it: certain species can cause serious problems for horses, cattle, and other livestock, and a plant commonly mistaken for clover (wood sorrel) carries its own concerns.
Clover Is Safe for Humans to Eat
Both white clover (the small one in your lawn) and red clover (the taller one with pink-purple flower heads) are edible. A nutritional analysis of five edible clover species found them to be rich in selenium and iron. Red clover in particular stood out as the most suitable for human consumption because it had low levels of toxic metals like arsenic, cadmium, and lead while being packed with essential minerals.
People use clover flowers in teas, salads, and as cooked greens. The flowers and young leaves are the most commonly eaten parts. Raw clover leaves can be mildly tough to digest in large quantities because of their fiber content, so light cooking or drying helps. There’s nothing in common lawn clover that would harm you or your children from casual contact or even from nibbling on it.
White Clover Does Contain Cyanide Compounds
White clover naturally produces small amounts of cyanide-releasing compounds called cyanogenic glycosides. In most backyard settings, the levels are low enough to be irrelevant for humans. However, certain environmental conditions can push concentrations much higher. Samples from some pasture fields have measured cyanide potential ranging from 307 to over 1,700 mg per kilogram of dry matter, a wide range that depends on growing conditions and plant genetics.
For a person casually eating clover flowers in a salad, this isn’t a practical concern. The amounts consumed are tiny, and cooking or drying breaks down these compounds. The cyanide issue matters more for grazing animals eating large volumes of fresh white clover daily.
Risks for Dogs and Cats
Common white and red clover are not considered toxic to dogs or cats. That said, eating any plant material can cause vomiting and stomach upset in pets, so a dog that grazes on a clover patch might have mild digestive issues without being truly poisoned.
The bigger concern for pet owners is confusing true clover with wood sorrel (Oxalis), a plant that looks strikingly similar. Wood sorrel has heart-shaped leaflets instead of clover’s rounded ones, but many people call it “clover” without realizing it’s a different plant. Oxalis species contain 7% to 10% soluble oxalates, which can cause kidney problems in animals that eat significant amounts. If your pet is chewing on a clover-like plant and you notice the leaves are heart-shaped or the plant has yellow flowers, that’s wood sorrel, not clover.
Horses and Alsike Clover
Horses face a genuine and potentially fatal risk from one specific type: alsike clover. This species causes a condition known as alsike clover poisoning, which attacks the liver. Affected horses show progressive weight loss, signs of liver failure, and varying degrees of neurological problems. The underlying damage involves scarring and abnormal growth in the bile ducts of the liver.
Alsike clover also causes photosensitivity in horses, where unpigmented skin (white markings, pink noses) becomes severely sunburned and blistered. Horses grazing on pastures that contain alsike clover are at risk, and the condition worsens the longer they’re exposed. If you keep horses, identifying and removing alsike clover from their pasture is worth the effort.
Red Clover and “Slobbers”
Red clover can become infected with a fungus that produces a toxin called slaframine, especially during cool, wet growing seasons. The fungus creates visible black patches on the clover. When horses or cattle eat contaminated clover (fresh or as dried hay), they develop profuse, dramatic drooling within hours. Other signs include watery eyes, diarrhea, mild bloating, and frequent urination.
The good news is that this condition resolves quickly. Once the contaminated feed is removed, animals typically recover within 24 to 48 hours, sometimes up to four days. It looks alarming but is rarely dangerous on its own. Checking red clover hay for dark patches before feeding it is a simple way to avoid the problem.
Sweet Clover and Internal Bleeding in Cattle
Sweet clover (a different genus from common lawn clover, though they share the name) poses the most serious livestock risk. When sweet clover hay is improperly dried and stored with too much moisture, soil fungi colonize the plant stems and convert a naturally occurring compound into a potent anticoagulant. This substance blocks vitamin K from doing its job in the clotting process, and without functional clotting factors, animals begin to bleed internally.
Cattle are most commonly affected. Animals that die from sweet clover poisoning show extensive hemorrhaging: bleeding under the skin, into body cavities, muscles, joints, and organs. The tricky part is that symptoms are delayed. By the time an animal shows signs of bleeding, the toxin has already been working in the body for days. Decontamination methods like activated charcoal are essentially useless once clinical signs appear because of this delay.
Treatment centers on restoring the body’s ability to clot. Vitamin K supplementation is the standard approach, but treatment can last up to four weeks. Blood transfusions provide an immediate supply of clotting factors in severe cases, though treating multiple large animals this way is rarely practical due to cost and availability. Prevention is far more effective: properly curing and drying sweet clover hay before storage prevents the fungal growth that creates the toxin in the first place.
How to Tell Clover From Its Lookalikes
The plant most often confused with clover is wood sorrel (Oxalis). Both have three-part leaves and grow low to the ground, but telling them apart is straightforward once you know what to look for. True clover has rounded or oval leaflets, often with a lighter chevron or V-shaped marking. Wood sorrel has distinctly heart-shaped leaflets that fold along a central crease, and its flowers are typically yellow or pink with five petals, rather than the ball-shaped flower heads of clover.
Wood sorrel is actually edible in small amounts and has a pleasant sour, lemony taste. But its high oxalate content (7% to 10% soluble oxalates) means eating large quantities could contribute to kidney stone formation in susceptible people or cause problems for pets and livestock. In small amounts as a trail nibble or salad garnish, it’s fine for most people.
If you’re looking at your lawn and wondering whether the three-leafed plants are safe, they almost certainly are. Both true clover and wood sorrel are common, widespread, and harmless in the quantities a child or pet would encounter from casual contact or the occasional taste.