Plants that produce flowers do so in order to reproduce. The flowers produce seeds which grow into new plants similar to, if not the same as, the parent plants. Flowers are a method of sexual reproduction, and may have either male or female organs, or both. All flowering plants are angiosperms and are the latest types of plants to evolve, following gymnosperms by 200 million years.
Some trees bloom with beautiful flowers, while others color their flowers green so they are not easily distinguished from the foliage. With the exception of the conifers, palms, ginkgos and gnetophytes, all trees are flowering vascular plants. Trees are characterized by having a single woody stem growing from the root system. The main stem is branched, typically above the soil surface, but sometimes at or below the soil line.
Smaller than trees, shrubs can be similar in appearance, but are usually bushier. They bloom in various colors and at different times during the season. Pruning shrubs allows gardeners to shape and train them for hedges or specimen planting, but pruning at the wrong time may eliminate the flower buds. Shrubs usually have multiple stems growing from a single root bundle.
Woody vines such as clematis are popular. They grow as high as 30 to 40 feet depending on variety, live a long time and have varying requirements of sunlight, moisture and food. Different varieties flower for short periods at different times during the growing season. By choosing several, gardeners can have flowers throughout the season with spectacular displays of color.
Annuals are short-lived flowering plants that grow from seed, mature and produce seed for the next generation in a single season. They put most of their energy into growing to maturity and reproducing. Annuals include many bedding plants, most vegetable plants and some herbs. In some cases, half-hardy perennials or biennials are sold as annuals in colder climates.
Longer-lived than annuals, perennials take a full season to mature. They go dormant during the cold winter months and reawaken in the spring. Perennials include many bedding plants, and a few vegetables and herbs. Typically sold as mature plants ready to flower, perennials may be more expensive than annuals, but pay for themselves since they produce flowers for several years, if not longer.
These plants spend an entire growing season establishing themselves before going dormant for the winter months. During the second season, they grow quickly to maturity and flower. At the end of the season they die, leaving the seeds from their flowers to start the next generation of plants. Some common vegetables, including carrots and parsnips, are biennial. A few bedding plants are also biennial. Biennial bedding plants are usually grown to maturity and sold as annuals, flowering the same season as they are planted.