All plants originate outdoors, but many are grown as houseplants, such as the popular and hardy cane plant. Because there are countless types of outdoor plants, gardeners usually group them in broad categories according to growth rate and the specific features of the plants. These specific features are then broken down into smaller groups, such as plants that grow well in hot sun, plants that have repeat flowerings and other such identifiers.
Perennial plants are those that bear leaves and/or flowers every year. These plants are very popular in most home gardens. They are frequently shrubs or bushes, such as roses, but they can also be flowers, like the popular columbine. Some perennials eventually die out after three or four years, while others continue to grow and spread unless you dig them up, such as the common lily. Other perennials only return yearly if the weather is warm enough. Geraniums, for example, are perennials in some parts of the country, but not in areas with very cold winters.
Annuals are plants that grow for only one season. These plants, which are most often flowers, complete their life cycle in one year. They are popular with gardeners because many of them grow and spread quickly, filling empty spaces in the garden with bright colors. Although many annuals easily reseed themselves, the subsequent growth arrives from new plants, not the original plant. Snapdragon is one such annual that reseeds itself very well. Other annuals include impatiens, primroses, pansies and marigolds.
Biennial plants are similar to annuals, but they complete the growing cycle in two years. During the first year, the plant devotes its energy to developing a good root system and growing foliage. In the second year, the plant blossoms and produces seeds and fruit. Sweet William is a popular biennial. Many vegetables, such as carrots and parsley, are biennials that are harvested during the first year, but are never given a chance to flower.
Trees are the most visually impacting of all outdoor plants. They can be loosely divided into two groups: coniferous, which are trees that produce cones (like the pine tree) and deciduous, which refers to trees that lose their foliage in the fall. Many hardwoods, such as oak, are deciduous trees. Most coniferous trees are evergreen, which means they do not lose their foliage, and they remain green all year long.
Succulents are plants that are found in very arid conditions. These plants cannot count on getting regular water from the soil or air, so they have adapted to their environments in order to survive. Succulents store water in the main body of the plant or in the leaves, such as the aloe plant. Most cacti, such as the barrel cactus, are succulents. The bottle tree is also a succulent plant.