For the best house plants you should have the best possible soil for them. This may sound like a big order, but actually it isn't. Today most home owners buy bagged soil and assume it is good. A potting mixture suitable for most house plants is a combination of loam, sand, peatmoss and/or leafmold. Loam is the name given to a soil which contains clay, sand, silt and humus. It varies from a sand loam to a clay loam, depending on the relative amounts of these two ingredients present. A medium loam is preferred, which may be obtained from arable land such as a cornfield or vegetable garden.
To do a really bang-up job in preparing soil for house plants the loam should consist of turfs cut from a rich pasture. But because the turfs should be cut in the spring and stacked for about six months prior to using the mixture and because many readers will have difficulty in obtaining it, we will forget the ideal loam for the time being. Leaf-mold, too, might present some difficulties because it takes about a year for tree leaves to decay.
The remaining ingredients are not ordinarily difficult to obtain. Horticultural peatmoss can be bought from almost any garden center or garden center. The sand should be coarse with particles ranging from 1/8 to 1/16 inch. Get it from a firm dealing in builders' materials. If the loam is deficient in humus (ask your county agricultural agent or state experiment station), buy packaged humus to mix with it.
For cuttings, seeds and seedlings, a "lean" mixture is required. Use equal parts of loam, sand and peatmoss in accordance with the character of the loam. If it is sandy use less sand; if clay predominates increase the amount of sand. The mixture should be thoroughly mixed and then tested for acidity. For most house plants the reaction should be pH 6 to 6.5; for acid-soil plants, pH 4.5 to 5.5. If the soil reaction is too acid correct it by adding 16 to 1 ounce of pulverized limestone to each bushel. Just in case there is not enough phosphorous in the soil, mix 1-1/2 ounces of superphosphate in each bushel.
For mature plants use a "fatter" mixture such as 6 to 8 parts loam, 3 parts peatmoss, 2 of sand by bulk; plus 4 ounces of a complete fertilizer with an analysis of about 5-10-5, and 1 ounce of calcium carbonate (pulverized limestone) to each bushel. Double the amount of peatmoss for azaleas and camellias.
For plants like begonia and saintpaulia (African-violet), which revel in soil containing ample organic matter and which do not demand acid soil, it is desirable to add an additional part of leafmold or humus.
Peatmoss, vermiculite (expanded mica, available under various trade names), and sand are primarily soil conditioners. They are usually sterile in the sense that they are free from injurious organisms; hence there is no need to sterilize them. They are also sterile in that they are lacking in plant nutrients, except for peatmoss, in which, however, they are in short supply and not immediately available.
It is best to sterilize (actually it is to pasteurize) the loam - also the leaf-mold, separately, if it is used. The simplest way of doing this is to put 1 inch of water in a saucepan, bring it to a boil, put in the loam dry, cover and let simmer for a half hour. The odor of cooking soil is not pleasant so to avoid domestic trouble I would advise doing it outdoors.
The flower pots (clay or glazed - not plastic) should also be sterilized together with the drainage material (potsherds or fine gravel). Plastic pots can be washed when you do the dishes. Care should be taken to prevent contamination by storing the pasteurized soil in a container such as a new garbage pail with a tightfitting lid.
It is possible to grow house plants without using soil by putting the plants in water; or by using a sterile medium such as flowerpot chips, coarse sand, vermiculite or sphagnum moss and watering with a nutrient solution.
Flowerpot chips can be made by breaking cracked or broken porous clay pots into pieces Va inch or smaller. If you do not have a supply of suitable pots, a soft porous brick can be broken up in the same way and used instead.
Many house plants are able to get along for months, or years even, in tap water. Included in this group are English ivy, Chinese evergreen, saintpaulia, red sister cordyline and airplane-plant.
The soil-less methods are for those who have difficulty in obtaining soil and also for the adventurous who are willing to take a chance. If you do not like to putter around, it is easy to buy packaged soils, sterilized and mixed ready for use. These can be quite good, or worthless, depending on the ethics of those who mix and package them.
Author Resource:
Thomas Fryd shares his knowledge at http://www.plant-care.com. Knowledge is power - get more power and find out more about red sister cordyline .