Proper care, plus the right environment, will give you a successful season indoors.
Back in the days before central air and heat house temperatures and humidity were just about perfect for most house plants. But today, with our central systems, proper growing conditions have all but vanished from the home. This does not mean, however, that indoor gardening should become a lost art. With a few alterations, there is no reason why you cannot have plants blooming on your window sills while white, powdery snows are blowing from the roof tops.
Correct Lighting for Houseplants
As you possibly already know, lighting is of utmost importance in indoor gardening because it furnishes energy for plant growth. Even those plants that thrive on filtered light will not set buds without some sun. This is especially true of African violets which actually welcome the weak winter sunlight.
Because most house plants do need sunlight in winter, they do best in a southerly exposure. An east window will do for plants that normally do not need direct sunlight. It must be remembered that plants will not grow or bloom as they should unless the amount of light they receive is about equal to that of their natural home.
In many houses, large foliage plants are often used to set off pieces of furniture along inner walls or in dark hallways. To keep these foliage plants healthy and growing, place a 150-watt incandescent bulb within 4 feet of each. The light must be turned on throughout the day and extinguished after sunset.
I am aware that sometimes it just isn’t possible to grow plants on window sills in certain homes. The windows may be too small or too high, or the decor may not allow it. If this situation exists in your home, do not fret. You can still garden indoors by purchasing plant-growing stands already equipped with proper lighting. These are inexpensive and are excellent for all small plants that-love filtered sunlight, such as the African violets, caladiums and gloxinias. Because of the built-in lighting system, the plant stands may be placed anywhere in the house.
Humidity and Houseplants
Humidity is a governing factor in the health of all plants. If the plant is expected to do its best, the relative humidity surrounding it night and day must be the same or close to that of its original habitat. When a plant originates in a definite amount of humidity, it adjusts its life processes to that particular amount of air moisture. All jungle plants that prefer filtered light demand a humidity as high as 90 per cent; subtropical plants, 50 per cent; temperate zone plants, 45 per cent; and desert plants, 5 per cent.
The most difficult problem facing today’s indoor gardener is maintaining the right relative humidity for the different kinds of plants he or she wishes to grow. Humidity is far more important than one might think, and cannot be shrugged off lightly. Low humidity is disastrous to plants — especially those of the jungle. If the surrounding air remains hot and dry, evaporation takes place very rapidly, drying off leaves and causing more rapid transpiration. (Transpiration is the escaping of moisture through the pores of the leaves.) A plant has been so constructed that there is a balance between the amount of moisture absorbed by the roots and the amount evaporated from the foliage. Plants will wilt in low humidity even though the soil contains sufficient moisture. If wilting continues over a long period, the plant will die.
Too high a humidity is not dangerous to most plants, except those of the desert. It causes them to become leggy and spongy. To maintain sufficient humidity, place pots on pebbles above the water level in shallow trays. Or, if your plants are on glass shelves over a radiator, keep a pan of water constantly on it. Enough water will evaporate to maintain a decent humidity reading. Several plants in a group will aid humidity by transpiration. Frequent spraying of the leaves with water will also go a long way toward keeping humidity at a high level.
Since all plants do not require the same amount of humidity, separate your plants into groups according to their air-moisture requirements, then keep just that one particular group in a suitable window. That way you can better control the humidity each group needs.
Inexpensive humidity indicators are great aids to indoor gardening. They will give you the exact humidity reading of the air around your plants, thus warning you when more moisture is needed. You will find that one water spraying can increase the humidity as much as 10 per cent in a few seconds.
Temperature and Houseplants
The third important growing factor in plant growth is the air temperature. Each type of plant demands the kind of temperature it originated in. Jungle plants require higher temperatures than other plants, although temperate zone and desert plants can withstand 90 to 100 degrees for a short time without harm. Low temperatures are actually the demons that do plant growth real harm.
In the plant’s natural habitat, temperatures naturally drop at night, and plants have adjusted their life processes accordingly. During the day, with energy from the sun, plants manufacture carbohydrates from the soil and water, and extract carbon dioxide from the air. When darkness falls, photosynthesis becomes an impossibility. Plants need food for growth so they turn the starches they manufactured during the day into sugars, and use them to build new cells.
Tropical plants can withstand a minimum of 65 degrees at night; subtropical plants, 55-60; temperate zone plants, about 45 degrees; and cacti will endure any temperature as long as it is above freezing.
Like people, all plants are healthier when they sleep in a cool room. The drop in temperature at night serves to stimulate the action of turning starches into sugars for growth. If temperatures remain steady for 24 hours, this process is not stimulated enough for proper growth and bloom.
If your plants remain on the window sill, surrounding air will automatically become copied by the pane at night. But if they are located where temperatures remain constant, remove them to a cooler spot at night, or lower the heat in the room.
As you become more accustomed to growing plants indoors, you will find that there are some plants that defy all rules pertaining to their particular group. For instance, camellias, which in reality are jungle plants, will drop their buds if temperatures rise above 65 degrees. This does not mean that you cannot enjoy growing these demanding plants in your home. Use an indoor thermometer to locate the warmer and cooler spots in your home, then station these plants where temperatures are suitable.
As winter creeps on, you will find that low temperatures, and not high ones, create problems at night. For instance, night temperatures may drop dangerously below the 65-degree mark during cold spells on the sills where African violets are growing. Protect them by drawing the shade, by installing a storm window, or by placing several thicknesses of newspaper between the plants and the pane. Hang a thermometer in each window where plants are growing, and do your best to maintain the right night temperature for each individual group.
To keep your plants healthy and happy, grow them in the kind of soil they are used to. One mixture will never do for all.
The jungle floor is not a thick layer of black topsoil as one might think. Because growth is so intense, organic matter is used up before it can turn into rich soil. The upper crust consists only of a thin layer of vegetable matter in the process of decay. Taking this into consideration, leaf mold and sphagnum moss are the chief constituents of jungle soil. A good potting medium for jungle plants should consist of one part organically enriched garden loam, two parts leaf mold, and one part coarse sand. If your soil is sandy like mine, use one part garden loam, one part sifted compost, and two parts leaf mold. The soil pH should be 5.5 or under.
Temperate Zone Soil
Temperate zone plants need darker soil rich in humus with a pH near neutral (7.0). The soil mixture I use consists of two parts garden loam, one part sifted compost, and one part leaf mold. Use one part sand if your soil is heavy.
The desert plant group, which comprises all forms of cacti, prefers a soil mixture of one part garden soil, two parts sand, and one part coarse gravel. The pH should be neutral or slightly alkaline.
Since the roots of plants that are potted cannot go off in search of food, I find it beneficial to add one table-spoon of ground phosphate rock, one of potash rock, and one of bone meal to each 6-inch pot when potting or repotting.
Pots to Use for Houseplants
It may surprise you to learn that the type of pots you use have a great deal to do with the health of the root systems. If at all possible use only clay pots. They have their own cooling system because moisture is drawn from the soil through the side walls by force of evaporation. Actually, the clay pot is capable of evaporating twice as much through its walls than from the surface soil. This beneficial evaporation has a cooling effect on the soil and the roots, resulting in healthier, happier plants.
How Much to Water Houseplants
Watering house plants requires a skill that can be developed quickly if the needs of the different plants are learned. In outdoor beds where plants grow all summer, you will notice that the soil remains moderately moist at all times. After rains drain away and the topsoil begins to dry, it absorbs moisture from the subsoil through capillary attraction. In such earth, only the soil particles are damp, with a multitude of air spaces in between. Roots are designed to absorb moisture and plant nutrients from the moist particles, and oxygen from the air spaces. If the soil is too wet, these air pockets are filled with water, thus shutting off the needed oxygen supply and hampering the natural growth processes.
I have found that it is not wise to water until the surface soil feels dry. Then, instead of watering from the top, I find it better to plunge the pots in water to within an inch of the rim. When the surface becomes moist, I remove them to the drain board to allow the excess water to drain off, then replace them on the sill. Three such dunkings a week are usually sufficient for my plants.
In reality, no one can say how often to water a house plant. It depends largely upon the relative humidity and the type of pot the plant is growing in. Clay pots may need watering every day, while others may get along with a watering every other day.
Above all, do not overdo the no-watering bit to the extent where the plant withers. Such a plant will take several days to recover after it finally is watered. Or, if water has been withheld too long, it may never do so.
If you care to take the trouble, there are a number of ways in which you might cut down on watering, thus saving time and root systems. First off, of course, make certain your soil mixtures contain plenty of humus to retain moisture. Secondly, if possible, use sheet moss as a mulch. This must be gathered in fall. I like to use green moss from beneath my weeping willows. After removing as large sheets as possible, I soak them in water for a few moments, then cover the entire soil surface of each pot with it. African violet lovers who lose plants because the leaves are burned by concentrated salts on the rims of the pots, will be happy to learn they can prevent this by draping green moss over the rims. African violets actually love the cool, moist texture of the moss.
Another good point to remember while watering is never to use cold water. It slows down the activity of the plant. Although water is in abundance, the chilled plant will wilt because it does not have the power to absorb enough moisture. Always bring the water to room temperature before giving it to the plants.
You can also cut down on watering by placing a porous clay pot in a non-porous container. There should be at least one inch of air space between the two. This will not interfere with the evaporating cooling system of the smaller pot, and will enable it to better resist the effects of a dry, overheated house.