Original document location http://edis.ifas.ufl.edu/MG031
Care of Plants in the Home1
Robert J. Black and Richard W. Henley2
Growing plants in the home has become very popular in recent years. Plants create an atmosphere of warmth and life that cannot be equaled by any other home furnishing.
Unfortunately, the environment in many homes is not conducive to growing plants. Many homes have inadequate light, temperature fluctuations, and low humidity. These adverse growing conditions offer a real challenge to the homeowner and point out the necessity for selecting plants to fit the growing conditions in the home.
FACTORS AFFECTING PLANT GROWTH
The environment in our homes will dictate which plants will grow lavishly or which ones will suffer. No other environmental factor is more important in growing good plants indoors than adequate light.
Plants differ greatly in their light intensity requirements. Plants with highly colored leaves, such as coleus and croton, and flowering plants and succulents grow best when placed in an area where they receive full sunlight. Others like ferns, philodendrons, and many other foliage plants grow well with indirect light. The light intensity requirements for many foliage plants commonly grown in the home are given in Table 1 . The light intensity can be determined with a light meter held at the level of the plants' foliage.
Artificial lighting can be used to supplement or replace natural light. Standard cool white and warm white fluorescent lamps are good sources of artificial light. Most plants grow well and are attractive in appearance when placed under a combination of cool white and warm white fluorescent lamps or cool white and grow-fluorescent lamps. There are a variety of grow-fluorescent lamps available from major manufacturers.
Fluorescent lamps are available in various sizes, shapes and wattage. In addition to the standard lamp sizes (15, 20, 30 and 40 watts), higher wattage lamps may also be obtained in 48 inch tube lengths and longer--up to 96 inches. These higher wattage lamps are called high output (HO), very high output (VHO), power groove, power tubes, or super-hi output lamps. Cool white, one foot square panel fluorescent lamps can be obtained in two sizes, 55 and 80 watts.
Standard industrial fixtures with white enamel or white porcelain reflectors are widely used by hobbyists. Fixtures that accommodate two 48 inch long fluorescent lamps are the most commonly used and inexpensive to buy. Strip or channel fixtures may be used with reflectorized fluorescent lamps.
It is important to order fixtures for the specific lamps that are to be used in them. Only lamps of the same wattage are interchangeable in fluorescent fixtures.
Table 1 . Light Requirements for Some Common Foliage Plants*
A day temperature of 65° to 75° F (18 to 24° C) and approximately 10° F lower at night, is satisfactory for most plants. The 10 degree drop at night enables plants to build new tissues. Plants grown in continuously high temperatures often become spindly and less resistant to disease and insect attack.
A sudden temperature drop can injure plants, and temperatures below 50° F (10° C) for extended periods may cause permanent damage to many plants. Wilting often results, followed by yellowing of leaves, and then leaf drop. Avoid placing plants in hot or cold spots. Few plants do well on top of a television set and almost none will survive the blast from a heating or air conditioning vent.
Most plants grow best at a relative humidity of 40 to 60 percent. Unfortunately, the average humidity in most homes is well below 40 percent, especially during winter months when heating systems are operating. When the surrounding air is dry, plants will often lose water from leaf tissues at a faster rate than can be absorbed through the root system. When this occurs, leaf tips become brown and flowering plants may lose flower buds.
Humidity levels in the home can be increased by installing an inexpensive humidifier. Humidity in the vicinity of plants can be improved by placing potted plants on a two or three inch bed of wet gravel. Water evaporating from the gravel increases the humidity around plants. The bottom of the plant pot should never be in or under the water, since this will cause a waterlogged soil which may result in root damage. Plants will furnish their own humidity when many are placed close together.
Good air circulation is necessary to the well being of plants. However, plants should be placed in draft-free locations. Areas where cross currents of air occur are not considered good for plants.
Clean, gas-free air is desirable for growing plants. Escaping gas from stoves and furnaces is sufficient to kill plants.
One common cause of indoor plant death is improper watering. When the soil remains saturated, root systems are unable to function properly because of lack of oxygen in the soil.
The amount and frequency of watering depend on the following variables:
- Potting Mixtures - Organic mixes retain more water than sandy mixes.
- Pot - Plants in porous (clay) pots require more frequent watering than those in nonporous (glazed or plastic) pots.
- Plants - There is a wide range of water requirements for different species of plants. Some plants should be watered when the potting mix becomes dry to the touch while other plants need to be watered before the soil becomes completely dry.
- Plant Size - Plants with a lot of leaves will need more frequent watering than those with a few leaves.
- Humidity - The lower the humidity, the more often a plant will need to be watered.
- Stage of Growth - When a plant is dormant (not actively growing) it will need less water.
The rule to follow in watering is to water when necessary. The following methods may be used to determine when to water:
- Touch - The most accurate gauge to follow is to water when the potting mixture becomes dry to the touch. Stick your finger into the mix up to the first joint; if it is dry at your finger tip, you need to water.
- Tapping the pot - When the potting mix in a clay pot begins to dry, it shrinks away from the sides of the pot. Rap the side of the pot with the knuckles or a stick: if the sound is dull, the soil is moist; if hollow, water is needed.
- Estimating Weight - As potting mixtures become dry, a definite loss in weight can be observed.
- Judging Soil Color - Potting mixtures will change from a dark to light color as they dry.
When watering is required, water thoroughly. Apply enough lukewarm (room temperature) water until it runs out of the bottom of the pot. This type of watering will accomplish two purposes. First, it washes excess salts out of the pot. Second, it guarantees that the bottom 2/3 of the pot is properly watered. Do not allow the pot to stand in water too long. Empty the drip saucer.
Application of water to the top of the soil mix is the most common method of watering container plants. However, watering from the bottom of the container with the use of a saucer or tray is a method used by many homeowners. Watering constantly from below brings nutrient salts to the soil surface. An excess of these salts may accumulate in the upper soil layer in four to six weeks and this can result in burning of the upper roots and/or stem. It is a good practice, therefore, to water thoroughly from the top once a month to leach excess salts out of the pot.
The success or failure of growing plants in containers depends to a large extent upon the potting mixture. There is no one potting mix which is infinitely better than any other. General requirements of a good container mix are:
- potting mix should be dense enough to support the plant,
- mix should have good nutrient holding capacity,
- texture of the mix should allow both water and air to pass through readily and yet retain some moisture, and
- mix should be free of pathogens and weed seed.
Generally, native soils are not ideal media for plants grown in containers. These soils need to be amended with peat, bark, perlite or sand to improve their physical structure and water and nutrient retention capacities.
Native soil should be sterilized to kill disease organisms and weed seed. Spread moist soil in a tray or pan and bake at 200° F for 20 minutes, stirring every five minutes.
Foliage plants grow best in potting mixes containing high levels of organic matter, such as peat. The following mixes are suggested for growing foliage plants:
- Two parts peat, one part perlite, one part coarse sand
- Two parts peat, one part coarse sand
- One part peat, one part coarse sand, one part pine bark
- One part peat, one part pine bark, one part perlite
Cacti and other succulents, on the other hand, grow best in sandy soils. An example of a good succulent mix is two parts soil, one part peat moss, one part perlite, and one part coarse sand.
Packaged potting mixes can be bought at local nurseries and garden supply dealers. These materials are convenient and often have been sterilized to kill disease organisms and weed seed. Some packaged soils are premixed with organic matter, perlite or vermiculite and are ready for immediate use. Other packaged media are primarily sterile soils which may need amending to make them more desirable soil mixes for indoor plants.
Soilless mixes consisting of various combinations of peat moss, perlite, and vermiculite are available at most garden supply dealers. These soilless media are lightweight, easy to handle, sterile and most contain fertilizers.
The foliage of most plants grown indoors should be cleaned weekly. Plants with hairy leaves, such as African Violets, gloxinias, and tuberous-rooted begonias, should not be wet, while the foliage of most others may be cleaned with a moist soft cloth. Clean foliage is favorable to healthy growth, to help control insects, and to keep plants looking attractive.
The growth rate of most plants indoors is much less than that of plants grown in a greenhouse. As a result, indoor plants do not need as much fertilizer as greenhouse plants. Also, rapid new growth is often undesirable, as plants may outgrow their locations.
Many problems associated with growing house plants are erroneously attributed to insufficient fertilizer. Poor growth is usually due to some other factor, such as insufficient light.
Interior plants under active growing conditions should be fertilized every two to three months. During winter months, or under conditions of low light, the frequency of fertilization should be reduced.
There are many special commercial materials available for fertilizing indoor plants. Most are effective and safe if used as directed. A complete fertilizer, one which contains nitrogen, phosphorus, and potassium should be used. Manufacturers are required by law to indicate the fertilizer analysis on the container label. This analysis is given in a series of numbers such as 10-15-10, 20-20-20, 14-14-14. The first number of the series indicates the amount of nitrogen; the second, the amount of phosphorus; and the third, the amount of potassium.
Fertilizers are available in many forms: water soluble powders and pellets, liquids, tablets, sticks, and time release pellets. The liquid and water soluble powders and pellets are diluted in water as directed and poured on the growing medium. The tablets, sticks, and time release pellets are designed to release nutrients gradually and evenly over a given period of time. The length of time during which these fertilizers are active will depend upon the formulation of the material, indoor temperature and watering practices.
When choosing a container for an indoor plant, several factors should be considered. The selection will depend upon the size of the plant and where it will be placed in the home. Containers too large or too small present an awkward appearance. The container must be large enough to provide space for root growth for at least one year. If the container is too large the nutrients are leached from the soil before new roots can reach them, and the soil mix may remain too wet.
Clay pots are porous and allow water to evaporate through the sides and, therefore, require more frequent watering than plastic, glass, metal, wood or glazed pots. For that reason, most amateurs who have a tendency to overwater are usually more successful with clay pots.
Containers without drainage holes should have a layer of coarse gravel placed in the bottom to allow a space for excess water. Another method of using containers without drainage is the "double-potting" technique. Pot the plant in a container that has a drainage hole and is one inch less in diameter and shorter than the container without drainage (decorative pot). Place several inches of gravel in the bottom of the decorative pot and place the potted plant on the gravel layer.
As the upper portion of a plant grows, the root system gets larger, eventually filling all the available space in the container and becoming pot bound. When this happens plant growth will be restricted unless more room for root growth is provided by repotting.
The frequency of repotting depends upon the rate of growth of a particular plant. Slow-growing plants may require repotting every two to three years, while fast-growing plants should be repotted annually.
Water the plant thoroughly several hours before removing it from the container. Then invert the pot and place your hand on the potting mix so the base of the plant is between the index and middle fingers. Next, tap the rim of the pot on the edge of a table until the root ball slides out of the container. Remove an inch or two of potting mix from the top of the root ball. If the roots are matted around the root ball (pot bound), force the roots apart and cut the entangled roots. Select a pot with a diameter equal to 1/3 to 1/2 the height of the plant. Usually, transplant to one size larger than the pot in which the plant was previously grown. Place a small piece of broken clay pot over the drainage hole to keep soil from draining through the hole. Do not include other aggregates in the bottom, since the aggregate actually slows water movement through the pot.
Cover the bottom of the pot with a layer of potting mix and firm with fingers. This layer of mix should bring the top of the root ball within one inch of the container top. Fill around the root ball with mix and firm gently. Water thoroughly and do not repeat until the potting mixture surface becomes slightly dry.
Improper culture may result in unattractive plants. Some of the common symptoms and conditions which may cause these are:
- Brown leaf tips or burned margins--may be caused by too much fertilizer or soil allowed to dry excessively.
- Yellowing and dropping of leaves--are caused by air pollution, low light intensity, chilling, over-watering or poor soil drainage and aeration, or root decay from soil-borne diseases or insect pests.
- Weak growth or light green or yellow foliage--is caused by too intense light, lack of fertilizer, root-rot or poor root system.
- Small leaves and long internodes--indicate too little light.
- Small leaves and short internodes--may be caused by lack of fertilizer or being grown too dry.
- Small new leaves and leaves curl under--regular type, may indicate too much light.
Mealybugs are soft-bodied insects covered with a white, powdery material. When mature, they vary from 1/5 to 1/3 inch in length and some species have long wax filaments extending from the rear of the body. They damage plants by sucking plant juices.
Spider mites are about 1/50 inch long when mature and may be greenish, yellowish, reddish or virtually colorless. They are commonly found on the undersides of the leaves. When plants are heavily infested, fine webbing will be noticed. Mites suck juices from plants through their needlelike mouth parts. A 10 or 15 power magnifying glass is very helpful in detecting infestations before severe damage occurs.
Aphids may be green, pink, black, brown, yellow or blue in color. They vary from 1/25 to 1/8 inch in length and may or may not have wings. They are pear-shaped, have long antennae and two short cornicles or tubes extending from the rear end of the body. Aphids suck plant juices and cause new growth to curl and become distorted.
Scales can be almost any color depending on the species. They are 1/8 to 1/3 inch long when mature and are surrounded with a waxy covering that may be circular, oval, oblong or pear-shaped. Scales are found on both sides of the leaves as well as on twigs and branches. They may be almost hidden in the crevices of stems or axils of leaves. Scales cause damage by sucking plant juices.
Whitefly adults are about 1/16 inch long, white in color and resemble tiny moths. When disturbed they will swarm about the plant. The nymphs are 1/16 inch in length, pale green in color, and flat and oval in shape. They are found on the undersides of the leaves and cause damage by sucking plant juices.
Fungus gnat maggots, Springtails and Psocids are soil pests that may damage the root systems of house plants. Fungus gnat maggots are white, worm-like in shape and about 1/4 inch long when mature. Springtails range in size from microscopic to about 1/5 inch long, are usually white in color and jump when disturbed. Psocids range in size from about 1/32 to 1/16 inch in length, are usually white to gray colored and may or may not have wings.
*Note: This information was taken from "Insects and Related Pests of House Plants and Their Control," Ornamental Horticulture Department mimeo by D. B. McConnell and D. E. Short.
Carefully examine any purchased plants to be sure they are free of pests. After bringing a plant home, isolate it for at least a month before placing it with other plants.
Always use sterilized soil for potting to help prevent infestations of soil pests such as nematodes, springtails, psocids and fungus gnats.
Spraying plants with a forceful stream of room temperature water every two weeks will remove many insects before they have a chance to become established. This procedure is best done outdoors or in a laundry sink. Spray the lower surfaces of the leaves where most plant pests are found. Spraying also keeps the foliage dust-free and the plants looking attractive.
Washing with soapy water and a soft cloth may be all that is needed to remove aphids, mealybugs and scale insects from broadleaved plants. Use two teaspoons of a mild detergent to one gallon of water.
If one or a few plants are involved, you may be able to control aphids and mealybugs by removing them with a toothpick or tweezers. Caterpillars may be picked off plants by hand and destroyed. Cutworms, slugs and snails may be found in their hiding places during the daytime and destroyed or picked from the plants at night when they come out to feed.
An easy way to control a light infestation of mealybugs or aphids is to wet or remove the insects with a swab that has been dipped in alcohol. Swabs recommended for babies are excellent. Be careful not to over apply, as alcohol may burn the foliage.
For severe infestations or where large numbers of plants are involved, chemical control may be needed. For recommendations on selection and application of insecticides and miticides, contact the Agriculture Extension Agent in your county.
Plants grown indoors are troubled with few plant diseases. This can be attributed in part to the low humidity within the home. Most plant diseases spread by spores which require moisture for growth.
Many problems commonly attributed to diseases are the result of unfavorable growing conditions. Overwatering is the primary cause of root and stem rot. Excessive watering causes an oxygen deficiency in the soil resulting in root death and subsequent rot. Often soil-borne fungi and bacteria will invade root systems which are weakened by an oxygen deficiency. Root rots can be prevented by using sterile, porous potting media, containers with adequate drainage holes, and proper watering. When root rot occurs, the top portion of the plant may be saved by air layering or by taking cuttings.
The most common and satisfactory method of propagating most house plants is by cuttings. A cutting is a portion of a plant taken from a parent plant. There are many types of cuttings, but the most important ones in propagating house plants are stem and leaf cuttings.
The rooting medium for cuttings should have good drainage yet hold moisture and be sterile. A suggested medium would be 1/2 peat and 1/2 perlite or coarse sand.
Root-inducing hormones can be used on plants which are difficult to root. When conditions for rooting are ideal, growth substances may reduce rooting time and permit a higher percentage of cuttings to root. Root hormones are available from garden supply stores. Follow directions on the container label when using rooting hormones.
Plants such as African violets, begonias, gloxinias, sansevierias, and most succulents are easily propagated from leaf cuttings. Leaf cuttings are of two types--those where new plants arise from the leaf tissue, such as Bryophyllum, rex begonia, and sansevieria (snake plant); and those where the roots and shoots arise from the base of the petiole, such as African violet and gloxinia.
Sansevieria leaves may be cut into sections about 3 to 4 inches long and stuck about one inch down into the medium. It is important that the section remain right side up. Roots and shoots will form from the section and should be removed from the leaf section when the new shoot is 3 to 4 inches long. The variegated sansevieria will not reproduce true to type using this method. To retain its characteristic, it must be propagated by division of the original plant.
Leaves of Rex begonia and other fibrous begonias develop young plants from their primary veins. Make small cuts across the larger veins on the undersurface of the leaf. Then lay the leaf right side up on a moist medium. Use toothpicks or wire to hold the leaf in contact with the medium. New shoots should appear in about two weeks. When the new shoots are 2 to 3 inches high they can be transplanted.
African violets and gloxinias can be propagated using entire leaf (leaf blade plus petiole) cuttings. Cut the leaf from the plant leaving 11/2 inches of petiole attached to the leaf. The leaf cutting should be stuck into the rooting medium only deep enough to keep the cutting upright and at an angle.
Most house plants root easily from stem cuttings. Terminal cuttings of 3 to 6 inches in length should be taken from healthy, vigorously growing plants. Make a clean cut about 1/4 to 1/2 inch below a node (joint) with a sharp knife. Avoid crushing the stem. Remove a few lower leaves from the cutting to prevent wilting, but the cutting should not be heavily defoliated. Stick the cutting one inch into the medium and firm gently so that it remains upright.
Stem cuttings can be rooted in plastic bags or in containers covered with plastic bags. The plastic cover keeps the humidity high but does not prevent oxygen and carbon dioxide movement in and out of the container. Set the container where it is exposed to daylight, but never in direct sunlight. Heat from direct sunlight will be trapped in the plastic bag and kill the cuttings.
Division is simply separating a large plant into two or more plants. Plant division is often used for African violets, sansevierias and many other plants that produce several shoots from a central growing point.
Division can be done by hand or a knife can be used to split the plant apart. Be very gentle and try to obtain as many roots with each plant part as possible.
Air layering is a method of plant propagation used to induce plant stems to root while they are still attached to the mother plant. It is an effective and fascinating means of propagation for large plants that have heavy stems. Many old, tall, spindly plants can be reclaimed by this method.
Select a healthy, vigorously growing main stem or lateral branch. At a point 12 to 15 inches below the tip, completely girdle the stem by removing a strip of bark 1/2 to 1 inch wide from around the stem. Another procedure is to make a long, slanting cut upward about 1/4 to 1/2 way through the stem. On large thick stems, make slanting cuts on opposite sides of the stems. Place a toothpick or matchstick into the cuts so the stem does not grow back together. Dust rooting hormone on the cut surface. Place a moist ball of sphagnum moss about the size of a baseball around the stem and over the girdle. Wrap a piece of plastic film, 8 to 10 inches square, carefully about the branch so that the moss is completely covered. Tie the ends of the plastic to form a moisture-proof package. Aluminum foil can be used instead of plastic film to cover the sphagnum moss.
After roots have penetrated the moss ball and are visible on all sides, the layer can be severed from the parent plant just below the moss ball. Remove the wrapping without disturbing the roots or removing the ball of moss and plant the layer in a container using a good potting mixture.
To simplify information in this publication, some trade names of products were used. No endorsement of these specific products is intended nor is criticism implied of similar products which were not mentioned.Table 1.