
But.... how do you know if it is a weed, or maybe a native plant whose seeds have been dormant, or something shared by a friendly critter?
You can check out the Calflora website database and learn about plants that grow wild in California - both native and weeds.
Or, if you think something might be overly invasive, go through the California Invasive Plant Council gallery - a very extensive collection of photos to find out if it is a landscape friend or foe.