Some plants grow as climbers all of the time, whereas others grow as climbers just part of the time. Poison ivy and bittersweet, for example, can grow as low shrubs when no support is available, but when support is given, they will become climbers. The growth form of a climber is based on very long stems. This has a dual purpose. Instead of spending energy in a large amount of supporting tissue, a climber may exploit rock exposures, other plants, or other supports for growth, allowing the plant to access sunlight with minimal effort.