By Russell T. Nagata
Hawaii County Administrator University of Hawaii at Manoa College of Tropical Agriculture and Human Resources
Even if we live in paradise, where beautiful plants can be grown year-round outside in the garden, many of us enjoy having plants in our indoor or covered living spaces.
Indoor plants can be divided into two general types: those we keep indoors on a temporary basis such as blooming plants and those that are more or less permanently indoors which are usually foliage plants. For both types of plants, certain rules apply to get the best out of your plants. One of the most important aspects at which to be proficient, is the watering of your indoor plants. Unless you have air conditioning or a breezy home, your plant will probably need less water than if it were growing outside. With plants growing in soil or soilless mix, it is best to maintain the soil in a damp condition and waiting for the soil to dry between watering. I use the heaviness of the potted plant to determine watering. To do this, it is important to remember how heavy the plant is when well watered.
When the soil appears dry and the pot is light, it is time to water. If you have a dish beneath the plant, water slowly until the water starts to flow into the dish from the bottom drain holes. Let stand for three to five minutes and drain any excess water away. Although some gardeners recommend that the plant wilt slightly before you water house plants, this is a risky practice since this will add stress to the plant and the response can be the loss of foliage. Also, in a hot and dry environment, the beginning of wilting can be a day or less away from the permanent wilting point, where the plant will not survive. Plants, like orchids, that are grown in coarse media like cinders, gravel, coir, or hapu`u can be watered by watering the media in the sink and allowing excess water to drain away. Since these types of media do not hold much water, it is best to water when media appears dry.
The second important item to consider for indoor plants is the amount of light for proper maintenance of plant functions. Remember that light is important for plant growth since it supplies the energy source that allows plants to manufacture chemical energy used in all aspects of plant growth and maintenance. Both light quality and light quantity are important considerations. Plants can be subdivided into groups based on the amount of light necessary for plant growth and maintenance. Those that require direct sunlight for more than five to six hours a day will probably not do very well indoors or on the covered patio. Then there is the intermediate group that is happy with some shade and sun. These plants will do well in a sunny window with morning or afternoon sun shining through. Individuals in the final group are those that can be happy in perpetual shade, those plants that are normally understory plants in the forest. These plants will do well without direct sunlight.
Plants growing outside or in a greenhouse at a nursery are in their active growth mode; the growers need the plants to be the right size for sale. Due to the conditions of lower light normally found within indoor rooms or patios, plants need to be acclimatized to conditions to be experienced indoors. Plant growth needs to be slowed down by withholding fertilization, reduced watering, and slowly lowering light intensity. Plants that are properly acclimatized will adapt better to being indoors. These plants will not go into shocked and will maintain most of their leaves. Those that are shocked will drop many of their leaves in response to the sudden lower light, etc.
When bringing new plants into your house, be sure that you are not introducing pests into your home. Insects, small invertebrates (slugs and snails), and small vertebrates (frogs and lizards) love to hide in the moist growing media. You do not want to introduce harmful pest, especially those like little fire ants, into your home. Before you bring any plant into your home, check for hitchhikers on the plant and in the media. A small stick with peanut butter smeared on the end can be used to determine if little fire ants are present in the potting soil or on the plant. Check for aphids, mealybugs, and other insects that excrete honeydew that will make a sticky mess in your home and encourage mold to grow on the sugar-rich substance.
To test your indoor plant skills, when you receive a beautiful poinsettia this holiday season see how long you can keep it indoors. Locate that spot in the house or patio with the right amount of light, water carefully, inspect for pests, and it should still look beautiful at Easter. The real flowers will have died and fallen away, but the colorful bracts which are really leaves should still be showy.
For more information on this and other gardening topics, please visit the CTAHR electronic publication website at http://www.ctahr.hawaii.edu/Site/Info.aspx or visit any of the local Cooperative Extension Service offices around the Island. I can be reached at firstname.lastname@example.org.