Identifying flowers and other plants is an important skill for every gardener to learn. Not only will it help you tell the difference between a weed and a marigold seedling, but it will also allow you to identify plants in public gardens or in the wild so that you can incorporate coveted specimens into your own garden. Learning the relationships between various plants will help you create a more healthy and thriving garden, too.
All plants are given a scientific name (also sometimes called their Latin name) which consists of a capitalized genus name and a lower-case species name. So, for example, the large-flowering raspberry has a scientific name of Rubus parviflorus and the dewberry has a scientific name of Rubus flagellaris. The fact that they are both in the Rubus genus tell us that they are related and may share a similar plant structure and growth habit. Scientific names are important since the common names of plants may vary from region to region---i.e., in parts of North America, the large-flowering raspberry is known as the "thimbleberry."
To identify plants and flowers, you'll need some good field guides and other books. Some plant ID books are arranged by flower color, with all the red flowers grouped together and all the yellow flowers together, and so on. However, this can be confusing, since blossom color can vary between individual plants, and what one person might call "lavender" another person might think of as "blue." Better choices are books organized by family, habitat or bloom time.
Some field guides and other plant identification books will have a "key" in the front or the back which will help you narrow down an ID without flipping through the entire book. A key will ask you a series of questions, such as how many petals the flower has or how the leaves are arranged, and will offer some suggestions for identification. The book should also have a glossary to help you determine what "basal" leaves are or what it means for a flower to be "irregular."
Structure and Habitat
To identify plants, you must learn to look not only at the flower but also to the structure of the leaves, stems, fruit and other parts of the plant. A plant won't always be in bloom when you find it, or the bloom might be damaged or deformed. Being able to recognize a plant by the leaves or fruit will allow you to identify plants at any time of year. Paying attention to where a plant or flower is growing will also be a big help in identifying it, since many plants are very particular about their environment, and may only grow in moist conditions or in shady spots. For wildflowers, you will also check the plant's known range.
A loupe, hand lens or magnifying glass will make it easier to examine the tiny details of a flower, and can also offer a unique perspective on an otherwise familiar plant. You may also want a plant press (a heavy hardcover book will work in a pinch) to preserve specimens for later study. Take care in gathering plants from the wild, however. Do not take more than one or two specimens, and never pick plants that are rare, threatened or endangered.