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HOUSEPLANTS |
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Most people have a houseplant or two. Houseplants are given as tokens of appreciation, as housewarming gifts or to cheer an ailing friend. Houseplants bring the cycles of nature indoors. Growing plants indoors expands the range of plants that can be enjoyed. Tropical and subtropical plants that cannot survive cold winters are adaptable to greenhouses and sunny windowsills.
Growing houseplants is a serious
hobby for many people. There is the Indoor Plant Society of
America, as well as societies for orchid, succulent, African
violet and cactus enthusiasts. Researchers are doing studies
to determine if houseplants can purify the air.
KEY CONCEPTS
I. Holistic Houseplant Care
II. Acclimatization of New Plants
Return to Introduction
HOLISTIC HOUSEPLANT CARE
There is really no such thing as a houseplant. People take plants out of their native habitat to grow them in their homes. These native habitats range from the warm tropics to cool mountain tops and from dry deserts to ponds. The indoor gardener should try to duplicate the plant's natural environment.
Plants with different cultural requirements are often potted together as gifts. These should be repotted separately to meet each plant's individual cultural requirements.
The holistic approach to houseplant care integrates all of the cultural factors affecting a plant's health. These factors include soil, air, light, moisture in soil, humidity, fertility, pests, temperature, ventilation, plant size, the container and rate of growth. The following diagram illustrates the holistic system of houseplant health.
Watering is the number one houseplant killer. The well-meaning owner often waters too often. People place houseplants on a watering schedule with no regard for the plant's use of water. Due to varying cultural factors and changes in seasons, watering should be done on an as-needed basis.
Because houseplants come from a variety of natural habitats, it is important for the owner to know how moist or dry the soil should be. With so many houseplants being tropical or subtropical plants, general watering recommendations can be made. These recommendations assume the potting soil is well-drained and appropriate for the plant.
Apply water when the top 1 to 2 inches of soil are dry. Measure this by pushing the index finger about 1 to 2 inches down into the soil. Soil moisture cannot be determined by sight, except when a plant is wilted. Plants should never be
stressed to the point of wilting. However, some houseplants
should be kept nearly dry while others must be constantly moist. There are two methods of watering houseplants. The most common method is to apply water to the surface of the soil. Apply water so it runs out of the bottom of the pot. Allowing water to run out of the bottom ensures that roots in the bottom 2/3 of the pot receive moisture. If the soil is excessively dry, or the plant is pot-bound, water may flow through the pot without wetting the soil. In these two cases a second method of watering should be used.
The second watering method involves setting the container in water until moisture can be seen on the soil surface. This method, called bottom watering, periodically allows the root system to become completely saturated.
Never allow the pot to sit in the excess water that has drained into the saucer. Discard the excess water that collects in the saucer. Otherwise, the soil will become saturated, forcing air out of pore spaces. Without oxygen the roots cannot respire and they will die. The air spaces in soil are as important to plants as water.
The white powder that builds up on the pot and soil is SOLUBLE SALT. Accumulation of these mineral salts is common in houseplants because the container retains excess fertilizer and the naturally occurring salts in tap water. Signs of plant problems that may be caused by excess soluble salts include reduced growth, brown leaf tips, dropping of lower leaves, smaller-than-normal new growth, dead root tips and wilting. When salts concentrate in the soil, water is drawn out of the roots causing dehydration. Excessive salt buildup will eventually cause the roots to die.
Leaching will remove excess salts. Remove white powder residues from the soil surface and the pot. Pour a volume of water equal to three times the size of the pot through the soil. Discard the water that passes through the pot. Alternatively, take the plant out of the pot, clean the pot, remove all soil from the plant's roots and repot with fresh soil. If soluble salts are a reoccurring problem, reduce the amount of fertilizer applied and consider using distilled water.
The following are general suggestions for watering houseplants:
- Know how moist the soil should be for each species.
- Check soil moisture level and apply water based on the plant's moisture requirements.
- Use room-temperature water. This maintains a more stable root environment. Allow tap water to sit for an hour in an open container for chlorine to escape.
- Avoid using water that has passed through water softening systems, unless it goes through a deionizer to reduce salt content.
- Avoid wetting the crown of the plant.
Light is essential for plants to photosynthesize. Survival of a plant in a particular location depends on the available light in that location. Houseplant culture requires a close look at the light available in a particular room. Ask these questions when considering light level:
- Which direction do windows face? South-facing windows receive the most intense light. Heat buildup may be dramatic and it can burn foliage. Houseplants that require direct sunlight should be set back 6 inches from the windowpane.
East- and west-facing windows have 2/3 of the light available through south-facing windows.
North-facing windows receive 1/5 of the light that south windows do. North windows are also the coolest.
- What things outside and around the window affect light? Trees and shrubs, buildings, awnings, curtains and dirt on the window affect the quantity and quality of light that houseplants receive.
- How far away from windows will plants be placed? Once out of the direct rays of sun, the level of light available to a plant drops drastically.
- Are nearby surfaces bright or dark? Light-colored walls reflect light onto plants. Dark walls absorb the light.
- What are the light requirements of the particular plant?
Houseplants may be classified by their light requirements. The three levels of light requirements are: low, medium and high.
Follow this test to determine level of light in a particular location. Hold your hand 12 inches above a sheet of paper. If there is a definite shadow, the level is classified as high light. If there is a fuzzy shadow, the light level is medium. And if there is no shadow, light level is low.
Some plants are short-day or long-day plants. Special care is required to produce blooms. Poinsettia, kalanchoe and Christmas cactus flower only when day-length is less than 12 hours. However, most flowering houseplants are not sensitive to day-length.
Houseplants with VARIEGATED leaves need more light than plants with plain green leaves. Variegated leaves have pale or colored sections that contain no chlorophyll. Chlorophyll is necessary for photosynthesis. Therefore, the rest of the leaf must be exposed to more light to compensate for the nongreen areas that cannot contribute to this life-sustaining process.
Houseplants will grow toward the source of light. Phototropism describes the plant's tendency to grow toward light. If plants are not rotated regularly, they will become disfigured. Turn plants on an as-needed basis to maintain fullness on all sides.
Too much light can cause leaves to curl at the tips, develop yellow or brown splotches, wilt or fade to a lighter color. Too little light can cause straggly growth, smaller new leaves, bud drop and reduced flowering. Internodes will be very long and variegated plants may revert to solid green if there is not enough light..
Remember, the light that comes in windows changes with the seasons. You may need to move some plants away from the strong sunlight that pours in through south-facing windows in the summer. However, in the fall and winter this south window may be ideal. Learn to recognize the signs of light stress and know the requirements of each plant.
If the light available is less than ideal, artificial light should be considered. Incandescent bulbs produce too much heat to be used with plants. Special grow lights are the best choice, especially for blooming houseplants. Fluorescent bulbs, one warm-white and one cool-white bulb are adequate for most foliage plants.
If artificial light is the main or only source of light for plants, the lamps should be lit 12 to 14 hours per day and be 6 to 12 inches from plants. Blooming plants will require up to 16 hours and should be no more than 4-6 inches away from lights. It is important that some indoor plants have a regular light/dark schedule.
Home temperatures fall into three categories: cool (55 to 65 degrees F), average (65-70 degrees F), and warm (70 to 85 degrees F). Most foliage houseplants grow best between 70 to 80 degrees F during the daytime, and 60 to 68 degrees F at night. Most flowering houseplants grow well with the same daytime temperatures, but at night a temperature of 55 to 60 degrees F is better.
Temperature extremes should be avoided. Extremes may cause no growth or spindly growth, foliage damage or loss, and even plant death. A good rule of thumb is to have night temperatures 10 to 15 degrees lower than day temperatures.
During extreme outdoor weather, check the temperature near windows where you have plants. Keep plants away from heat registers, radiators, fireplaces or where the air conditioner causes drafts. Flowering plants are very sensitive to both warm and cool drafts.
HUMIDITY is the amount of water vapor present in the air. Some plants require high humidity to survive. For others, extra humidity is ideal, but they will survive at normal home humidity levels. A third group should have low humidity.
For plants that require high humidity, the level in their vicinity must be raised. Most indoor humidity levels are not adequate for plants that require high humidity. There are a variety of ways to raise humidity: cluster plants together, humidify the air or place plants on a tray of moist pebbles. Misting plants is not effective for raising humidity.
The need to fertilize houseplants varies with rate of growth, age of the plant, desire for growth, and growing season. Frequency of feeding can vary from every two weeks to every several months during the growing season. A general rule for application frequency is fertilizing at half the recommended strength, every 2 weeks from March to September. Do not fertilize most plants during winter months. Winter's reduced light and temperature result in little or no growth. Most houseplants are dormant during winter.
Houseplant fertilizers come in several forms: granular, crystalline, liquid, tablet and spikes. Most houseplant fertilizers are fairly concentrated. Never exceed the recommended application amount. Oftentimes, applications should be even more dilute than recommended. Label recommendations are based on the ideal conditions in greenhouses.
Spikes have the disadvantage of creating a high concentration of nutrients in the soil around them. This burns nearby plant roots. Liquid and crystalline forms of fertilizer are mixed with water and applied to the soil.
When applying fertilizers solutions to the soil surface, make sure that some of the solution runs out the bottom of the pot.
This ensures distribution of nutrients throughout the soil. Do not allow the pot to sit in this runoff.
When considering fertilizer applications, it is important to be aware of the growth rate of houseplants. Slow-growing plants need less fertilizer; faster growing plants will need more. Flowering plants usually require both more light and more nutrients. Type of POTTING MEDIUM influences when to fertilize. Newly repotted plants in soil-based mixture
DISEASES
Houseplants grown under correct cultural conditions have very few disease problems. Poor growing conditions stress and weaken plants. Consider all factors affecting a plant's environment when looking for the source of a disease. A symptom may have more than one possible cause, and many problems result in the same or similar symptoms.
Diseases are most often a result of overwatering, poor soil conditions, too much or too little humidity and lack of air movement. General actions to take include isolating or quarantining diseased plants, removal of diseased tissues and possibly chemical treatment.
Root, crown and stem rots occur when the soil is kept too wet or the plant is damaged by cold temperature. In these cases, remove diseased tissue or take a cutting of healthy tissue to start a new plant.
Leaf spots can be caused by fungi, bacteria or growing conditions. Water drops remaining on leaves or high humidity are necessary for infection. Whatever the cause, the affected leaves should be removed and the probable cause corrected.
Insects and mites may be a problem even under the best growing conditions. They come into the home on new plants or with plants which are put outside for the summer. Insects may come in on clothing or when the door is open.
Scale insects are among the most difficult to control. These insects are mobile when young, but then settle and secrete a protective covering that can't be penetrated by insecticides. The best control is a systemic insecticide.
Soft-bodied insects like aphids, mealybugs and whiteflies are easily controlled with insecticidal soaps and pesticides like malathion. Insecticidal soaps are relatively effective for mites. These tiny spiders feed on the underside of leaves. Miticides also effectively control this pest. See Fact Sheet 2012, Reference House.1 for details on identification and control of mites on houseplants.
Soil with a high organic content may result in infestations of fungus gnats and springtails. These insects feed primarily on decaying organic matter, but occasionally damage healthy plant tissue. Avoid soil mixes with a high organic content, remove fallen leaves from the soil surface and drench the soil with an appropriate pesticide as explained in Fact Sheet 2114, Reference House.2, on fungus gnats and Fact Sheet 2070, Reference House.3, on Springtails.
A few common houseplants are poisonous. All or portions of these plants may cause mild-to-fatal reactions if eaten by children, adults or pets. The American Medical Association has edited a book on poisonous plants which should be used as a reference. Anthurium sp. (flamingo flower), Diefenbachia sp. (dumbcane) and Nerium oleander (oleander, rose bay) are poisonous. The seeds of Ricinus communis (caster bean) and the bulbs of Hyacinthus orientalis (hyacinth) are also poisonous. The local poison control center should be consulted for treatment of poisoning caused by these plants.
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