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Butterfly Farming Larval Host Plants Milkweeds (Asclepias)

Is Milkweed (Asclepias) Toxic?

Yes, Milkweed (Asclepias) is considered toxic to humans, as well as to many animals. The entire milkweed plant, including its leaves, stems, flowers, and milky sap, contains toxic compounds known as cardenolides. These substances can be harmful if ingested or come into contact with the skin or eyes.

Cardenolide, technically a steroid,

While milkweed toxicity varies among species, the general rule is to exercise caution when handling or consuming any part of the plant. The sap can cause skin irritation, redness, and swelling. If it comes into contact with the eyes, it may cause irritation and redness. Ingesting milkweed can lead to symptoms such as nausea, vomiting, abdominal pain, and, in severe cases, more serious health issues.

Toxic Milkweed sap. Photo: Emma Pelton/Xerces Society

However, it is important to note that some insects, particularly Monarch Butterflies and their caterpillars, have developed a tolerance to milkweed toxins. In fact, Milkweed is the primary food source for monarch caterpillars, and they have the ability to sequester the cardenolides from the plant, making themselves unpalatable to predators.

The toxic latex in Milkweed makes Milkweed Butterfly Caterpillars inedible to small creatures, like the Robin who sticks to Earthworms for her diet.

If you suspect exposure to milkweed or are concerned about its toxicity, it is advisable to seek medical attention or consult with a poison control center for guidance.

Wear gloves, if possible, when you plant Milkweed, and certainly try to keep your fingers out of your eyes while doing gardening of any kind. The soil harbors every kind of bacteria and virus.

So while Milkweed are toxic, and its latex can be an irritant to humans, in the end it is worth the risk, because together, by planting more Milkweed, we can restore Milkweed Butterflies… one day at a time!

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