Some people even consider certain plants pests. They are commonly referred to as "invasive plants" or "exotics". Invasive plants are introduced to California from other parts of the world. Because the natural pest diseases, or weather conditions that keep the plants in check in their homeland are missing in California, these "invasives" have taken over natural areas and have smothered our native plants. For more information on invasive plants, what they look like, and/or what you can plant instead, visit: