The most vigorous roses I've ever seen are volunteer Rugosas that stand eight feet high in a grove that covers half an acre. The plants have stems 2 inches through at the base. This grove is in pure sand at the edge of a swamp but is fed by runoff from a richly organic meadow higher up.
When we speak of roses, most of us mean the modern hybrid tea which, as one outstanding authority described it, "is a damned poor excuse for a shrub." We must remember that the rosebush of commerce is grown (grafted) on an understock which was selected as much for the convenience (ease of propagation) and profit of commercial growers as for its vigor and ability to recover after transplanting. The understock Rosa multiflora japonica has one weakness; it regenerates new roots so poorly after planting that sometimes a year or two is needed to allow it to make an adequate new root system. To illustrate: I dug up some rosebushes which had been planted in clay two years before. I found the bushes had made few roots and these few were stripped off in the digging operation. The same varieties planted in loose, friable Gardener's Loam not only grew plenty of new roots but made 25 per cent more top growth.
A FEW TOUGH PROBLEMS
There are very few soils that will not grow good roses. Thin whitish and gray clays found occasionally on older farmlands in the
East, pure sands without any organic matter, and the alkali soils of the West present problems too difficult for most gardeners to try to overcome.
Otherwise, any soil can be made suitable for roses. One proviso is to add all the organic matter you can afford, up to 25 per cent by volume. Provide good drainage and adjust pH to a reading between 6.0 and 6.9, and roses will grow.
One bit of nonsense to avoid with roses, unless time hangs heavily on your hands, is the old idea of digging out a pit 36 inches deep, laying down small rocks or broken bricks for drainage, adding a layer of organic matter and filling in with rich soil. I can't see any profit in such a deeply prepared pit for roses. Their roots are too feeble to take advantage of the improved soil depth; they probably would never get a chance to feed on that layer of organic matter buried 36 inches down. The 24-inch depth of double trenching should be adequate for the root growth of hybrid garden roses.