Determine if the weeds are grassy weeds, sedge weeds or broadleaf weeds. Grassy weeds grow narrow, ribbon-like blades, and leaves form in sets of two. Sedge weeds are similar to grassy weeds, but the leaves form in sets of three. Note that sedge weeds are sometimes classified as grassy weeds. Broadleaf weeds flower and are more like small plants, with wide leaves that branch out from the stem.
Examine the grassy and sedge weeds as they grow. Take note of the seeds and their characteristics, such as the color and texture. Note how tall and wide they grow as well.
Examine the leaves on broadleaf weeds. Note if they are lobed, hairy, heart-shaped, feather-like, toothed or fleshy, to name a few. Also, notice their growth pattern. They may spread, form rosettes or have whorled leaves, for example.
Dig up a weed, including the roots. Take note if it has fibrous roots, rhizomes, bulbs, tubers or stolons.
Take pictures of the weed as a reference. Include pictures of the roots, the seedlings, the flowers or seeds and the leaves.
Use your notes and pictures, and visit an online database, such as one from a nearby university website or county extension site. Many of these sites have pictures you can click through, while others ask questions to you help narrow down your search.
Match the online picture or description to your pictures and notes for a final conclusion as to the weed’s identity.