Trying to identify plants can be an avocation, a necessity or a school project. Whether you want to catalog the wildflowers on your nature walk or figure out what that errant stranger is in your vegetable garden, correct plant identification follows a methodology that includes observation, collecting evidence and comparing your findings with a plant identification reference. After you have collected observations on the plant and its environment, compare your description and pictures with the characteristics and pictures of plants in your reference books to make an identification.
If the plant you are trying to identify has flowers, that is particularly helpful, because flowers are a feature that is straightforward to describe and compare. When describing the color of the plant's flowers, try to be specific.
Think of the color names on a 12-segment color wheel with six solid colors---red, blue, yellow, green, orange and purple; and six blended colors named for touching segments on the color wheel, such as yellow-green and red-orange. Then add color names for flower colors that are mixed with white, such as lavender (purple with white) or pink (red with white). Add adjectives such as "light" or "gradient shade" if appropriate.
Count the number of petals and observe whether they are evenly distributed or some petals are significantly longer than others are. The flowers on some plants are really clusters of many, small flowers. Add information on the size of the flower and any interesting variations such as variegated, striped, or dark-colored center. See if the plants have more than one flower on a stem and note their relative placement.
Several characteristics of plant leaves will help make the correct identification. For an individual leaf, describe the outside edges. Plant reference books use terms like smooth, sinuate (smooth but with curves), dentate (the edge has little teeth or sharp points), serrate (teeth bent like a saw blade) and lobed.
Note the over-shape of the leaf such as oval, spear-like, or narrow; and how the leaves are attached to the stem. Leaves may be attached alternately or opposite one another. Some plants' leaves form a whorl at the end of the stem. Describe the color of the leaf and any color variation within an individual leaf.
General Characteristics and Environment
The general characteristics of the plant are its size, shape, and broad category (e.g. vine, grass, shrub, tree, flower, etc.) The environment includes the conditions around the plant you are trying to identify that may add or eliminate candidates in the final identification process. Start with noting the geographical location of the plant. Ideally, select reference books that are limited to your location. There are hundreds of thousands of plant types and your first task will be limiting your plant identification search to those that are most likely found in your area.
Also, consider the time of year since flowers do not bloom all the time on all plants and leaves change color with the seasons on some plants. Note whether the plant is growing in full sun, partial shade, or complete shade.