This section is from the book "The Florists' Manual", by William Scott. Also available from Amazon: The Florist's Manual.
We don't all have the ideal soil on our places, even if we are in the country with twelve acres to skin. It will pay to procure the right quality, even if at infinite trouble. Some think that one variety is better suited by a heavier soil than others. The soil we have seen used by the Hudson river growers was a heavy. yellow loam. Perhaps the ideal soil would be the top three or four inches off a pasture, where the grasses were red-top and white clover. The roots of timothy and red clover would be rather coarse. What is it that gives so much merit and virtue to decaying sod? It must largely be its physical condition, or mechanical, the presence of the fibre making it porous and enabling water to pass freely through. One of the most successful growers of Rhinebeck called lately and in alluding to violets remarked: "I am not patricular about soil so long as it is leachy, for they want lots of water," meaning that he wanted a soil that he could water freely without its retaining too much moisture.
When this sod can be secured it should be made into a pile of convenient size. In October you have much more time than in the short spring. Add to the pile one-fourth of cattle manure. If your soil pile is made in the fall there is no need of the manure being rotten, for by spring, and with a chopping down and one or two turnings, the manure will be absorbed by the soil. At the last turning over of the soil heap, one peck of bone flour can be added to every cubic yard of the compost. Whether you grow on shallow benches, deep benches of one foot, or solid beds, at least six inches of new soil should be supplied every spring, for violets are deep rooters and go a long way in search of food. In case of solid beds, when removing the top six inches of soil you should fork over and mix in some manure another six inches deep.