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Proper Soil

Plant roots must have air, food and water. Potting soil must be porous enough to allow drainage of excess water and to admit oxygen (soil aeration) needed by the roots.

Garden soil may appear ideal for potting indoor plants but actually causes problems. This soil may be wonderful for outdoor gardening under natural conditions, but after a few months the garden soil becomes hard and almost rock-like in a plant pot. Plants in garden soil grow satisfactorily for a month or two, but soon the lower leaves turn yellow and the plants become unthrifty. This problem is the result of poor drainage and the lack of soil aeration due to improper soil structure. Most garden soils become compacted with time and house plants grow poorly in compacted soil.

A proper soil mixture is of utmost importance to a house plant because the roots are restricted by the pot. A good potting soil should have the capacity to retain some air and moisture and yet drain well and hold nutrients. Sand or perlite added to the soil will improve aeration and drainage. Clay or organic matter will help retain water. Organic matter, plus commercial fertilizers, will maintain adequate nutrient levels. Modern "soilless" potting medias do not contain soil so the addition of fertilizer is required to provide all essential plant nutrients.

For general use, a good soil mix includes approximately equal parts of good garden loam, organic matter (preferably peat moss, although well-rotted manure or leaf mold will do) and sharp sand or perlite (Figure 1). When sandy soil is used in the mixture, reduce the amount of sand or perlite.

Always use pasteurized soil when repotting at home. This can be purchased at a local store, or soil can be pasteurized at home.

Figure 1