Tropical flowers and plants can offer color and leaf textures for both indoor and outdoor gardens. Some flowers, like orchids and water lilies, have some varieties that originated in tropical areas and other varieties that originated in temperate regions. A plant of tropical origin may need to be grown as a seasonal plant or brought indoors for the winter, unless you live in U.S. Department of Agriculture Hardiness Zone 10 or 11.
Although temperate orchids tend to grow in soil under the protective forest canopy, many tropical and sub-tropical orchids have adapted to grow above ground on tree bark. Tropical and sub-tropical orchids grow well in a bark medium, but can also do well in very loose, fast-draining potting soils and media. The light and temperature requirements of your tropical or sub-tropical orchid will depend on the variety. Some orchids need good light, while other varieties, more adapted to grow in dense tropical forests, may do better in partial shade. Tropical and sub-tropical orchids do best with between 50 and 80 percent relative humidity. Use a humidity tray if you need to raise humidity. Humidity trays are ceramic trays that you fill with gravel and water. As the water evaporates, it creates a zone of higher humidity around your orchid.
Tropical bromeliads are similar to orchids in natural growth patterns. Bromeliads tend to grow on the bark of trees or on sheer cliff faces. Like orchids, they do not harm the trees on which they grow; they use trees primarily for support. However, some bromeliads grow in soil. Bromeliads tend to do best with loose soil that drains well. They do not need a lot of soil fertility, and tend to be tolerant of shady, dry conditions, making them ideal as indoor houseplants.
There are a wide range of tropical water lilies, including lilies that bloom during the day and lilies that bloom at night. Water lilies grow from soil underneath the water of a pond or in soil in the bottom of pots. When planting in a pond, try to cover between 50 and 75 percent of the surface area. A rule of thumb is to plant one full-sized lily plant for every 10 square feet of pond surface area. Dwarf tropical water lily varieties are available for cultivation in pots. The hardiness zones in which tropical water lilies will winter over will vary greatly, depending on the variety. Some will not survive winter, and will need to be re-planted every year. Other lily varieties will survive winter in zones as cold as USDA Zone 4. However, some cold-hardy water lilies may be temperate--not tropical--lilies.