Plants have been cultivated indoors for 3,000 years. Early indoor gardening is thought to have begun in Greece by women who grew herbs indoors for the Festival of Adonis. Orangeries, or rooms of citrus plants grown indoors, were common during and after the Renaissance. The year 1830 marked the invention of the Wardian case, a miniature greenhouse that enabled gardeners 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 came from the tropics and were not cold–hardy outdoors, thus requiring indoor cultivation. A number of plants from these early expeditions are still in cultivation today and are good houseplants. Indoor landscapes such as planters filled with plants in shopping malls and office spaces are known as interiorscapes. 

UNDERSTANDING TROPICAL PLANTS 

Most plants grown indoors come from tropical and subtropical regions of the world. These places are typically warm and humid–very different from the homes and offices where tropical plants are often grown today. Understanding where plants come from helps make sense of their care and handling needs. Tropical regions, for instance, have seasons that vary by the amount of rainfall that occurs; there is generally a wet season and a dry season. Depending upon where plants are located in their native habitats, they may be accustomed to particular conditions.  

BENEFITS OF INDOOR PLANTS 

Indoor plants can improve the quality of life for people in a variety of ways. They move and reduce building pollutants by cycling air through themselves and, in the process, cleaning it. Indoor plants are a good addition to homes and office spaces. Studies have shown that people near green spaces have greater feelings of happiness and well-being.   

SUCCESS WITH INDOOR PLANTS 

No two indoor plant species are 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 them in areas suited to their cultural needs.   

Many factors influence the care that individual plants need.   

 LIGHT 

The most important factor in growing plants is light requirements. Plants make their own food through photosynthesis by converting light energy into food.    Different plants survive in different light conditions.  Always keep plants a few inches away from a window to avoid temperature extremes.   

  • Low–light plants: Plants that prefer light from a north–facing window include Philodendrons, Pothos, Sansevierias, Ferns, Aglaonemas, ZZ plants, and Spathiphyllums. 
  • Medium–light plants: Plants that like filtered light, like that coming through sheer curtains, include Spider plants, Ficus, Begonias, Peperomias, Palms, Dracaenas, Anthuriums, and Phalaenopsis. 
  • High–light plants: Plants that like full sun from a south–facing window include Cacti, succulents, citrus, Aloes, and most flowering plants. 

 WATER 

The second most important factor in growing houseplants is water. Most plants die from overwatering. Make sure pots have adequate drainage so plants do not sit in water for long periods of time. Check for soil moisture by sticking your finger in the top layer of soil which will help determine whether the plant needs to be watered.  Know the watering requirements of each type of plant you grow.     

 A plant’s container makes a big difference in the amount of water the plant needs. Clay or terra cotta containers dry out more quickly than plastic or glazed clay containers. Most plants do fine if they are kept evenly moist, drying out slightly between waterings.

HUMIDITY 

Most tropical plants are native to areas with 40-80% relative humidity. In the winter months, homes can have humidity levels as low as 15%. Using a portable humidifier near your plants can help them through the winter months. You can also elevate the humidity around indoor plants by placing groups of them on top of pebbles sitting in water–filled trays.  As water evaporates from the trays, humidity around the plants increases. Misting plants is also a good way to elevate humidity, though plants with hairy leaves like African Violets do not like to be misted. 

 SOIL MIX AND REPOTTING 

It is important to select the proper potting soil or soilless mix for growing your plants. While general mixes work well for most plants, some plants like orchids and succulents benefit from a specialty mix. These mixes are available at any nursery or garden center.  

Repot when the plant has outgrown its current container. The best time of year to repot is in the spring when new growth is emerging. Select a pot size 1 or 2 inches in diameter larger than the existing pot. It is important not to choose a pot that is too large because your plant could easily be overwatered. Plants thrive when grown in containers with drainage holes. If you select a container without a drainage hole, be sure to add a layer of gravel at the bottom before putting the plant in it. This will help keep the roots from rotting.   

FERTILIZER 

It is important to fertilize plants because the soils they grow in do not contain the essential nutrients they need to thrive. There are two major types of fertilizer available for houseplants. 

Liquid Fertilizer:
Most houseplants benefit from being fertilized once a month with liquid fertilizer during the period of active growth, generally March through October.  During the summer months you can increase the frequency of fertilization to every two weeks.  Knowing your plant is important to understanding its fertilization needs. Just as water, soil, and light requirements differ for various types of plants, so do fertilizers. Garden centers sell specific formulations to meet different plant needs. If you do fertilize regularly it is important to flush pots with fresh water once a year to remove fertilizer salts.  Use enough water so that it runs out of the bottom of the pot.   

Slow–Release Fertilizer:
Slow–release fertilizers are granular fertilizers that can be applied to the surface of the soil or mixed into the potting soil when planting. They slowly release their nutrients over a longer period of time which helps avoid overfertilizing a plant. For the busy plant grower, slow–release formulations are particularly helpful since they can be applied less frequently. 

PESTS AND DISEASES 

Indoor plants have pest and disease problems just like outdoor plants. Cleanliness is the key to minimizing these problems. Be sure to remove affected leaves and stems at the first sight of a disease or pest problem. When bringing a new plant into your home, be sure to inspect it carefully for insects or diseases that could harm it or spread to other plants in your home.   

Pests:
The pests most often found on indoor plants are aphids, mealybugs, whiteflies, spider mites, and scale. Thrips are generally problematic on flowering plants. Insecticidal soaps or horticultural oils are usually effective means of treatment for these pests.  You will need to re-apply the product weekly until the pest problem disappears.   

Diseases: 
Prevention is the most effective way to keep plants healthy from diseases. Once diseases are present, they are nearly impossible to eliminate. Following the proper growing requirements described above (appropriate light, water, humidity, soil, and fertilizer) will help keep your plant healthy and better equipped to fight off potential infections.