Gardeners living in subtropical regions of the United States, where temperatures rarely rise above 100 degrees Fahrenheit or experience frosts, have many choices in ornamental plants. Whether looking for a groundcover, flowering shrub, tree or perennial, a wide variety of plants are suitable for subtropical conditions. Many of the same plants that grow well in the ground in subtropical regions of the United States will do quite well planted inside containers in cooler areas of the country.
Shell ginger (Alpinia), also called shell flower, is a perennial flowering shrub that grows well in USDA zones 8 through 11. It produces long spikes of green foliage and spreads by underground rhizomes. Cup-like plumes of white flowers mixed with pink, brown and red are born on a long spike throughout late spring and summer. Gardeners can utilize shell ginger in gardens for a tropical effect, as a screening or hedge plant, or inside large containers. Plants grow up to 12 feet in height with a 3- to 5-feet spread. It tolerates a variety of well-draining soils and prefers frequent watering. Gardeners may find the ginger stalks as they die are messy looking, requiring frequent pruning. Shell ginger is suitable for areas located not directly on the coastal waters as it has a medium tolerance to salt spray.
Bromeliads (Bromeliaceae genera) is a perennial flowering groundcover that is hardy in USDA zones 8 through 11. Gardeners in cooler regions should grow bromeliads inside containers. Plants work well as groundcovers, in borders, tropical gardens and as houseplants. There are many cultivars with both green and gray-green foliage and flowers vary from 1 inch in height to almost 12 inches. Flower colors vary among cultivars and include pink, blue, violet, white, yellow, red, orange and bicolor. Some cultivars have spiny edges. Bromeliads grow in full sun to full shade with partial shade optimal. Height and spreading habit depends upon the particular cultivar, as some varieties grow barely 6 inches in height and others 2 to 3 feet, with the same variable spreading habit. Bromeliads prefer well-draining soil and are quite drought tolerant once established. They will not tolerate growing in soggy conditions as plants develop crown rot.
Japanese aralia (Fatsia japonica), also called paperplant, is a perennial shrub well suited for growing in subtropical gardens. It features large green leaves and clusters of small white flowers that bloom throughout winter. Japanese Aralia gives a tropical effect to mixed gardens and does well in shady areas, as screening plants or planted inside containers. Due to the plant's dense foliage and woody nature, it has a tendency to attract rats and termites, so gardeners should keep this in mind when selecting a planting site. Japanese Aralia grows best in full to partial shade. It reaches up to 8 feet in height with a 10-foot spread at maturity, growing at a medium rate of speed. It prefers well-drained soils, with regular watering. Once mature, the plants have a moderate tolerance to drought conditions.