Identifying an unknown plant in your yard is a matter of knowing a little biology and doing a lot of observation. You might even want a magnifying glass to check out the details involving the numbers, shapes, and sizes of the following:
What you'll be doing, especially if you begin without knowing anything about the plant, is called keying. Plant identification keys, found online, can quickly and easily identify plants, but they usually focus on a specific region or a certain type of plant, such as a weed or tree.
Some identification systems are dichotomous, meaning "divided into two parts." This type of plant identification process starts with two choices. When you've made your choice, you go to the next two choices, and so forth until you identify the plant. It usually takes six to nine choices to make the identification.
Some plant identification systems offer multiple choices. They are multichotomous or polyclave keys, so they takes fewer steps.
The more details you know about the plant you're identifying, the better. Some plant characteristics might not show up until later in the year or even until a plant matures.
It's helpful to look at pictures of plants already identified, especially if you can use a reliable source. But beware: Plants can change at different times of the year and during the phases of their life cycles.
Plant experts at your county extension service or botanists at a local college or university might be able to help you with identification. To give them the best information, preserve a sample of the plant by pressing it flat (not recommended for fruits or berries), or keep it for a short time in a bag in the refrigerator until you can show it to someone who can help.
Botanists group all the world's plants into families -- groups that share common characteristics. You might need to learn a little botanic Latin, but knowing some of the basics takes you to your goal faster.
Here are a few starting points about common plant families:
Almost every flower in the aster family (Asteraceae, one of the largest plant families) resembles a daisy. Think sunflower, blanket flower, yarrow, chrysanthemum, osteospermum, and marigold.
Plants in the mint family (Lamiaceae) often have square stems, leaves in pairs up the stem, and aromatic foliage. Think mint, sage, rosemary, lamium, Russian sage, coleus, and lamb's-ears.
Plants in the lily family (Liliaceae) usually grow from bulbs; have long, thin leaves; grow with six petals and six stamens; and form a seed capsule inside the flower. Think lilies, dog's-tooth violet, fritillaria, agapanthus, tulip, mondograss, and hosta.
Plants in the rose family (Rosaceae) usually have woody stems, large flowers with five petals, many stamens, and simple or compound leaves. Think rose, strawberry, apple, cherry, plum, peach, flowering quince, cotoneaster, and firethorn.
Plants in the olive family (Oleaceae) often have woody stems, showy flowers with four petals, and leaves in pairs opposite each other on the plant stem. Think forsythia, lilac, jasmine, privet, and lilac.
There are dozens of differences among members of each family. For example, many cultivated roses have more than five petals.
Once you begin digging into a plant's "family tree," you'll be enchanted with the variables nature and plant breeders have provided for our gardens. Learning the tools to identify plants adds to gardening enjoyment.