Book excerpt: Companion planting has a long history of use by gardeners, but the explanation of why it works has been filled with folklore and conjecture. Plant Partners delivers a research-based rationale for this ever-popular growing technique, offering dozens of ways you can use scientifically tested plant partnerships to benefit your whole garden. Through an enhanced understanding of how plants interact with and influence each other, this guide suggests specific plant combinations that improve soil health and weed control, decrease pest damage, and increase biodiversity, resulting in real and measurable impacts in the garden.