Native Neighbors Play Nasty!

Did you know some of California's most beloved native plants are secretly waging chemical warfare on their neighbors? Manzanita (Arctostaphylos sp.), sagebrush (Artemisia californica), and bay laurel (Umbellularia californica) all release allelopathic phytotoxins, volatile chemical compounds that inhibit the germination, growth, and survival of nearby plants. Sagebrush leaves release volatile terpenes that can prevent certain annual herbs and grasses from germinating nearby, reducing competition and resource use.

Terpenes such as Camphor, one of the most toxic individual terpenes, and 1,8-Cineole (Eucalyptol), interfere with normal growth and development of competing plants, sometimes moving through the air and sometimes spreading through the soil. Another notable producer of these phytotoxins is the Eucalyptus family, which releases compounds that make the soil inhospitable to most California native species and allows a monoculture forest to develop and grow.

Why does this matter to you? Well, knowing how plants interact with each other and the environment is crucial to designing and maintaining a healthy garden. Planting incompatible plants, including those who suppress or are suppressed by other plants, can lead to upsetting or unexpected plant losses, even when they are all technically “healthy. So, don’t get attached tot he idea of planting a nice dense groundcover under your manzanitas. It won’t do well, and it isn’t because of water or light: It’s because the Manzanita is doing what it evolved to do!