THE U.C. SYSTEM
One of the most complete methods for using special soil mixes ever developed is described in the publication "The U.C. System for Producing Healthy Container-Grown Plants," by Dr. Kenneth Baker, available for $1 from the University of California, Los Angeles 24, California. The publication recommends a system of growing plants which gets around the defects of John Innes Composts and also describes methods for overcoming diseases, pests and other problems. While primarily for commercial growers, the U.C. system should be of great value to anyone working with the special problems involved in growing plants in containers.
As stated, it is almost always advisable to sterilize soil (and pots, etc.) before use. This is most commonly done by steam (heat) or by chemicals. With any of the several chemical sterilants now on the market, be sure to follow package directions exactly.
SPECIAL SOILS FOR ROSES
Fortunately, some of the furor over special soils for roses has died down. I can recall a time when mere mention of that subject was an invitation to bitter arguments.
At the moment, the cow-manure-and-clay school seems to have lost out completely. I have not seen this system of growing roses mentioned in any article for the past year. (At one time, at least 95 per cent of all articles on roses included an admonition that if you wanted to grow the Queen of Flowers, you'd better have clay soil and be prepared to beg, borrow or steal several yards of cow manure. If you didn't, you risked being boycotted by all right-thinking rose lovers.)
Cow manure lost out to ordinary fertilizers when that ambrosial product disappeared from within easy reach of city gardeners. Rose growers on or near farms still use it as one of their special privileges. I can't pretend that I am not envious, or that I scorn it. At the same time, I am not unaware of the fact that persistence of blackspot
fungus in many a manure-fed garden can be traced directly to survival of spores in a cozy bed of damp cow manure over winter.
The preference for clay in rose beds has persisted longer. Even today, the notion that roses prefer clay pops up from time to time in print. An amusing item of contradictory advice appeared in a recent encyclopedic English book on roses. In one chapter the author advises against firm planting of rosebushes, while in another chapter he says he favors clay soil.
If truth be known, roses will survive in almost any soil, from a sandy loam to a stiff clay, so long as they have all the food and moisture they want. Actually I would say the lighter the soil the better the root growth.