Plants and gardens have a greater purpose than simply to be an eye catching source of food.
While mainstream medicine largely continues to deny the inherent healing capacity of natural plants and herbs, the insect world is abuzz with activities that confirm the plant world to be nature's medicine cabinet. According to a new study published in the journal Ecology Letters, the Monarch butterfly routinely uses medicinal plants to help its offspring resist disease and infection.

Researchers observed that Monarch butterflies prefer to lay their egg larvae on milkweed leaves, so they decided to investigate why this is the case. They discovered that milkweed plants contain vital compounds that help the larvae to stay healthy.

"We have shown that some species of milkweed, the larva's food plants, can reduce parasite infection in monarchs," explained Jaap de Roode, an evolutionary biologist at Emory University, and author of the study. "[W]e have also found that infected female butterflies prefer to lay their eggs on plants that will make their offspring less sick."

There are many types of milkweed plants, and some contain very high levels of cardenolides. Cardenolides are toxic to predators, but safe for Monarch butterflies. So when Monarch butterflies eat milkweed rich in the chemical, or lay their larvae on it, they build up a natural resistance to invading predators. The same chemical also helps to stop parasites that can develop in the butterflies' intestines and kill them.

Mark Hunter, a chemical ecologist from the University of Michigan who collaborated with the research team on the study, believes that the findings hold promising implications for humans as well.

"When I walk around outside, I think of the plants I see as a great, green pharmacy," he said. "But what also strikes me is how little we actually know about what that pharmacy has to offer.