If a weed is by definition an unwanted plant, novice gardeners may wonder why they need to go through the trouble of identifying a lawn weed before removing it. Gardeners should do this because some weeds are invasive plants and may require extra control measures, some weeds are poisonous and should be removed, and because not every chemical or mechanical control method works across the board. California's weed databases offer an easy tool for accurate weed identification.
Examine the leaves of your weed, writing down all details you observe. Note the leaves' size, shape, color (on the top and bottom), texture and arrangement along the stem. Most lawn weeds fall into two to three categories: grassy weeds, broadleaf weeds and sedge (similar to grass).
Note information about flowers on the weed, if your lawn weed has flowers. Not all do. Include details about the flower color, number of petals, scent and shape.
Photograph your weed for ease identifying it later.
Check California weed identification databases to accurately identify your weed plant. The California Invasive Plant Council provides a list of invasive plants broken down by geographic region; the University of California Davis lists most weeds commonly found throughout California. Browse images of these weeds until you've located the one in your yard, using the photograph and the information you gathered to make this positive identification.