What can I plant in my garden to keep pests away?

Doesn't every organic gardener want to know this? We don't want to use pesticides, so we want to know what herbs deter pests, what flowers deter caterpillars, and what plants repel specific insects that plague our gardens.

While scientific research on the topic of companion planting for pest management is still in its infancy, blog posts, books, and articles abound with ideas. But what suggestions are based in science and which ones are based in old wives' tales? 

In today's episode of the Beginner's Garden Podcast, I share 4 principles for using companion planting for organic pest control.