Indoor Tropicals
Fact Sheet 
Horticulture Services Division
Capitol Gallery
600 Maryland Avenue SW, Suite 3300
Washington, DC  20024

Plants have been cultivated indoors for 3,000 years.  The origin of indoor gardening is thought to have been in Greece by the women who grew herbs indoors for the Festival of Adonis.  Orangeries, rooms of citrus plants grown indoors, were common during and after the Renaissance.  The year 1830 marked the invention of Wardian Cases, or miniature greenhouses, which allowed people to grow ferns and other tropical plants in the same humid conditions as the plants’ native habitats.  Botanical collecting expeditions and world trade increased the number of species available for indoor cultivation.  Many of the plants brought to Europe were from the tropics and were not cold hardy outdoors, necessitating indoor cultivation.  Many of the plants brought from these early expeditions are still in cultivation and are good houseplants.  Florida is now the center of production for many foliage and flowering houseplants in the United States.  Interiorscapes are indoor landscapes such as planters filled with plants in shopping malls, museums and office spaces.  Interiorscapers are people who care for the indoor plant displays.
UNDERSTANDING TROPICAL PLANTS
Most plants used as indoor plants come from the tropical and subtropical regions.  Subtropical regions include places like south Florida that rarely freeze, but are not in the tropical zone.  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 seasons vary by amount of rainfall, not temperature. There is generally a wet season and a dry season.  Depending upon the location of plants in their native habitats, they may be accustomed to  varying conditions.  Plants native to mountains in equatorial regions may be used to cooler temperatures than plants that grow in the lowlands.  The New World Tropics is in the Americas and the Old World Tropics is in Africa, Asia and the South Pacific. 

Many tropical areas are warm and humid--very different from homes, shopping malls, museums and offices where tropical plants are typically grown today.  Understanding where these plants come from will make their care and handling make more sense and be much easier.  Some plants that are not traditionally thought of as indoor plants will thrive indoors with proper care.

 REASONS FOR INDOOR PLANTS
Indoor plants can improve the quality of life for people in different ways.  Indoor plants remove and reduce building pollutants. Plants cycle air through themselves, and in the process, clean it.  Indoor plants are also a good addition to homes and office spaces because they are alive and changing, and pleasant to the eye.  Studies have shown that people overlooking green space have a higher general overall attitude of happiness and well being. 

SUCCESS WITH INDOOR PLANTS
Indoor plants are not all the same.  There are plants to fit every area of the home, except for dark closets!  To ensure long term success with your indoor plants, select and place plants in areas suited to their cultural needs. 

Many factors influence the combination of care that individual plants need.  The amount of light, water, humidity, and fertilizer needed can be affected by the soil mix the plant is planted in, the container and other factors.  The following guidelines are general and may be changed for a specific plant in a specific location.  Always consult a reference book with specific plant care questions. 
 
LIGHT
The most important factor in growing plants is light requirements.  Plants make their own food through photosynthesis.  They convert the light energy of the sun into glucose, or sugar.  Plants survive in many different light levels.  It is generally not a  good idea to put plants right up against a window, as it can get very hot in the summer and cold in the winter.  Always keep plants back from the window a little bit to avoid temperature extremes. 

Low light plants:  Plants that like light from a north facing window—philodendrons, pothos, sansevierias, ferns, aspidistras, ivy
Medium light plants:  Plants that like filtered light through a sheer curtain—spider plants, ficus, begonias, peperomias, palms, dracaenas,  wandering jew, spathiphyllums.

High light plants:  Plants that like full sun from a south facing window—ficus, hibiscus, chrysanthemums, poinsettias, coleus, cactus, citris, aloe, jasmine, kalanchoe, most flowering plants

WATER
The second most important factor in growing houseplants is water.  DO NOT OVERWATER your plants.  A few other watering tips:  Use room temperature water.  Do not use softened water.  Make sure that pots have adequate drainage so that plants do not sit in water for long periods of time.  Do not water your plants on an arbitrary schedule.  Water them when they need water.  Check this by feeling below the top layer of soil to notice the moisture level. 

A plant’s container makes a big difference in the amount of water plants need.  Clay or terra cotta containers dry out more quickly than plastic or glazed clay containers.

Some plants need more water than others.  Most plants will do fine if they are kept evenly moist, drying out slightly between  waterings.  Some plants need to be watered more frequently than others.  Some ferns need to be watered almost every day.
 
For Further Reading
Chiusoli, Alessandro and Maria Luisa Boriani.
Simon and Schuster’s Guide to Houseplants.  Fireside, 1987.

Clarke, Graham and Jane Courtier. 
Indoor Plants:  The Essential Guide to Choosing and Caring for Houseplants. Reader’s Digest Adult, 1997.

Taylor’s Guide to Houseplants.  Boston:  Houghton Mifflin, 1987.

Raworth, Jenny and Val Bradley. 
The Complete Guide to Indoor Gardening.  New York:  Abbeville Press, 1998.
 

 HUMIDITY
The areas that most tropical plants come from have between 40-80% relative humidity.  In the winter months, homes can have as low as 15% humidity.  To elevate the humidity around indoor plants, set groups of plants on trays filled with pebbles with water to evaporate in them.  Misting plants is also a good way to elevate humidity.  Do not mist plants with hairy leaves, like African Violets.

SOIL MIX AND REPOTTING
The soil mix plants are potted in makes a big difference in their watering schedule and overall health.  Straight potting soil from the nursery does not provide enough drainage.  Mix one part potting soil with one part perlite as one mix option.  The other mix option is one part potting soil, one part peat, one part perlite. 

Repot only when needed—usually about once a year.  Repot in the spring when new growth is emerging.  Move up in pot size gradually—move plants into pots that are larger in diameter by 1-2 inches. 

FERTILIZER
Most houseplants can be fertilized every three to six months.  It is important to flush pots (water until it runs out the bottom of the pot) once a year  to remove fertilizer salts.  Liquid fertilizer and time release fertilizers are the two easiest methods.

PESTS AND DISEASES
Indoor plants have pest and disease problems just like outdoor plants.  Aphids, mealybugs, whiteflies, spider mites, and scale can all be present on indoor tropicals.  Washing the leaves with plain water or insecticidal soap will often help the problem.  Cutting back the damaged or infected plant material is a good cultural remedy. 

 

Researched and written by Katie Elzer, 2000.