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"Poisonous" does not mean deadly. Some manifestations of toxicity are subtle. The dose, as always, determines if a plant is safe source of nutrients or a toxic hazard.

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BRIEF: Is alfalfa really a poisonous plant?

If the information on your web page is to believed, most of the dairy cattle and horses in this country(USA) should have been dead a long time ago. Alfalfa has been grown as a hay crop for feeding to these species for many years. Clover, both red and white varieties, are very common pasture plants throughout the USA. Johnson grass, although not intentionally planted, is a common plant in pastures in the midwest and plains states. What is your source for stating that these plants are poisonous?


Alfalfa and clovers continue to be fine forages when properly grown, harvested, carefully preserved and fed to the appropriate species in appropriate amounts. They can cause significant toxicological problems if not used properly, however. Toxic plants, including feed plants and foods, can cause suffering, economic loss and permanent injury without lethality, so lethal effect at low doses is not a criterion for inclusion on our web pages. Grass and clover hay are great feeds, but they come with enough interesting biology to make our list. We will continue to depend on forage specialists to help hay producers provide us with nutritious, safe legume forages Examples of problems with these legume forages include, but are not restricted to: 1) Alsike clover, for some reason, causes severe liver damage in horses, along with the phototoxicity and death that often accompanies liver damage. I do not know what the toxic principle is and I was pretty skeptical of this when I first heard about it, but have seen enough cases and read documentation of others that there is no question in my mind this species is involved somehow. Perhaps directly, perhaps as a host for a toxic organism, but alsike is definitely required for the effect. 2) Fresh legume forage (alfalfa, red and white clovers mostly) is notorious for causing bloat in ruminants, even to the point of threatening life in some cases. 3) Several species of clover, especially red clover, can be host to Rhizoctonia leguminicola, an endophytic fungus that produces slaframine. This compound causes excessive salivation at modest doses easily obtained on infected pastures, and swainsonine-like effects at very high doses (probably above natural intoxication levels). 4) Saponins found in alfalfa limit its use for swine and poultry. 5) Canavanine in sprouts and seeds can and have cause lupus-like symptoms in humans. People who have sought to lower blood cholesterol by eating the seeds and obsessed individuals eating 300-450g per day sprouts have displayed these symptoms in 3 cases that I know of. We an did experiment a number of years ago in which we fed 50g alfalfa sprouts per day for a month without any ill effects on the undergraduate subjects, except an increase in aversion to sprouts (50g is A LOT of alfalfa sprouts). 6) Powerful phytoestrogens (isoflavones in clovers, coumestans in alfalfa) can play havoc with breeding programs and animal performance. This is not as severe as it once was, but one should keep an eye on this when trouble-shooting fertility problems and introducing new pest-resistant lines of legume forages. 7) Any feed can get moldy if not properly dried or ensiled, but I think alfalfa harvested in the damp summers of the East are particularly susceptible to this. This in turn can cause both respiratory and GI problems for livestock, especially horses. 8) Some animals are allergic to specific forages. This can include alfalfa. 9) Rich in calcium and protein, alfalfa can be the agent of nutritional imbalances if not properly rationed into an animal's diet. This can be a particular problem for horses and bulls.