Rabbits generally avoid milkweed in the wild, but they can and sometimes do eat it. Milkweed contains toxic compounds called cardenolides along with a sticky white latex sap that makes the plant distasteful to most mammals. However, milkweed is not a guaranteed rabbit deterrent, and if a rabbit does eat enough of it, the consequences can be serious or fatal.
Why Rabbits Usually Avoid Milkweed
Milkweed plants have two layers of defense against being eaten. The first is physical: a thick, milky latex sap present in all parts of the plant that is sticky and bitter. The second is chemical: compounds called cardenolides (a type of cardiac glycoside) that are toxic to most mammals and many insects. Together, these defenses make milkweed distasteful enough that most animals, including rabbits, will pass it over in favor of other food.
This is why milkweed sometimes appears on “rabbit-resistant” plant lists. For gardeners trying to protect a pollinator garden, milkweed is generally a safer bet than lettuce or clover. But “resistant” is not the same as “proof.” Tufts University’s pollinator research specifically flagged swamp milkweed as a species that “fed more rabbits than pollinators” and recommended planting it with caution. So while many rabbits leave milkweed alone, hungry or curious rabbits will nibble it.
When Rabbits Do Eat Milkweed
Lab research has shown that adult rabbits can eat milkweed without showing immediate signs of poisoning, which complicates the picture. In controlled experiments, rabbits readily consumed common milkweed. Even more striking, researchers found that baby rabbits could be “imprinted” on milkweed through their mother’s diet. When a mother rabbit ate milkweed during pregnancy or nursing, her offspring actually preferred milkweed over other foods in choice tests, even though it’s toxic. This preference developed even when the mother ate milkweed a full month before becoming pregnant.
Wild rabbits are most likely to eat milkweed when other food sources are scarce, when young plants have lower concentrations of latex and toxins, or when the rabbit simply hasn’t learned to avoid it. Pet rabbits with access to a garden may sample milkweed out of curiosity without the same instinctive avoidance that wild rabbits develop.
How Milkweed Harms Rabbits
The cardenolides in milkweed work similarly to the heart medication digoxin. They disrupt the balance of electrolytes in heart muscle cells, interfering with the heart’s electrical signals. This can cause an abnormally slow or irregular heartbeat, and in severe cases, complete heart block and sudden death.
Beyond the heart, other toxic compounds in milkweed affect multiple body systems. Rabbits that ingest a significant amount may experience:
- Digestive problems: abdominal pain, bloating, and diarrhea
- Muscle effects: tremors, weakness, and inability to stand
- Neurological signs: incoordination and seizures
- Breathing difficulty: slow, labored respiration
Narrow-leafed milkweed species tend to produce the most severe neurological symptoms, including seizures and respiratory failure. In livestock, as little as 0.1% to 0.5% of an animal’s body weight in dried milkweed can be lethal. For a 4-pound rabbit, that translates to a very small amount of plant material.
Why Rabbits Are Especially Vulnerable
One feature of rabbit anatomy makes any toxic plant more dangerous for them than for many other animals: rabbits cannot vomit. They have a powerful muscular valve at the entrance to their stomach that effectively prevents anything from coming back up. Most animals that eat something toxic can at least partially protect themselves by throwing up, but rabbits have no way to expel what they’ve swallowed. Once milkweed is in a rabbit’s stomach, the toxins will be absorbed.
This means that even a small amount of milkweed that might cause temporary nausea in another animal could deliver its full toxic payload in a rabbit. A pet rabbit that chews on milkweed in a garden doesn’t have the safety net that a dog or cat might have.
Not All Milkweed Species Are Equal
There are over 100 species of milkweed in North America, and they vary considerably in how toxic they are. Most fatal poisonings in animals come from species high in cardenolides. Common milkweed is moderately toxic, while narrow-leafed species tend to be the most dangerous, producing severe neurological symptoms before death. Butterfly weed, popular in pollinator gardens, is generally considered less toxic than common milkweed, though it still contains some level of these compounds.
Dried milkweed retains its toxicity, which is one reason it’s dangerous when mixed into hay. Fresh milkweed’s bitter latex usually deters animals from eating large quantities, but dried plant material loses that bitter taste while keeping its poison. If you’re feeding a pet rabbit hay from a field where milkweed grows, check for dried milkweed stems mixed in.
Protecting Your Garden and Your Rabbit
If you’re growing milkweed for monarch butterflies and worried about rabbits destroying it, the good news is that most rabbits will leave established milkweed alone. Young seedlings are more vulnerable since they have less latex and are tender enough to attract foraging rabbits. A simple wire cage around new plants for their first few weeks is usually enough protection.
If you have a pet rabbit that spends time outdoors, keep milkweed out of areas where the rabbit roams freely. While many rabbits won’t touch it, the risk isn’t worth taking given that rabbits can’t vomit and the toxic dose is small relative to their body size. Signs of trouble after a rabbit has been near milkweed include sudden loss of appetite, lethargy, bloating, muscle tremors, or any change in how the rabbit moves or breathes.