There are over 350,000 species of plants in the world and more are added every day. Learning the basics of identifying plants will enable you to know if a plant is invasive, useful or possibly poisonous. When you know how to identify a plant, you'll know whether you can use it in landscaping or if you should pull it out. You'll also be able to tell if the plant is native to the area.
Try to determine if the plant is a tree, bush, moss, vine or herb.
Look at the leaves. Are they monocot, or simple leaf, like grass or corn? Are they diocot, or compound leaves, like a bean? Are the leaves alternating or are they directly across from each other? Are the veins parallel or opposite? Is the surface fuzzy, smooth or rough?
Draw, photograph or write every detail you can about the plant. Include its color, size, shape, smell and any flowers. Does it grow upright or low to the ground? Does it grow in groups or clusters? If you're making a reference book you should prune and press the plant.
Look the plant up in a field guide. There are field guides for trees, wildflowers and weeds. They include pictures, growing information, and common and scientific names
Use a botanical key if you still can't make identification. A forking key is the type used most often. The key asks two questions about the plant. After you answer the one that fits your plant, it will ask two more. The pattern will be repeated until you have identified it. You'll need to know a lot of details to make an accurate identification.