Plants grown indoors are often from tropical and sub-tropical regions where the weather is warm and humid. The tropics is the region between the Tropic of Cancer, 23½ degrees north of the equator, and the Tropic of Capricorn, 23½ degrees south of the equator. Tropical plants are accustomed to varying conditions within the tropical environment.
The New World Tropics is in the Americas and the Old World Tropics is in Africa, Asia and the South Pacific. Some tropical areas receive rainfall each day. The area has a wet season and a dry season and heat variation between lowlands and mountains. Plants that grow in mountainous regions are used to cooler temperatures than ones that grow in the lowlands.
Indoor tropical plants create their food from sunlight through the process of photosynthesis. Their natural tropical environment is often filtered light. They need varying levels of light but should not be placed in direct light next to a window. Flowering tropical plants such as coleus and kalanchoe need more light than ferns, philodendrons and ivy.
Tropical environments have 40 to 80 percent relative humidity year round. Home environments may have as low as 15 percent relative humidity in the winter. Increase humidity for tropical plants by placing them in groups on trays filled with pebbles. Placing 1 inch of water in the tray creates the humid atmosphere that tropical plants need. Misting plants with a spray bottle of water also increases the humidity.
Soil Mixtures and Re-potting
Tropical plants need re-potting once a year.Spring is a good time for re-potting because that is when new growth begins. Potting soil that is porous and has good drainage helps tropical plants develop healthy root structures -- the optimum potting soil is 50 percent perlite. Clay or terracotta pots dry out more quickly than plastic pots.
Tropical plants grow well in humid conditions but do not respond well to over-watering. They easily become waterlogged and disease prone when their roots sit in water. Adequate drainage is essential. Room temperature, non-softened water is recommended by the Smithsonian Gardens website. Plants should be watered when the top of the potting soil is dry to the touch.