This section is from the book "Commercial Gardening Vol4", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
There is no time in the year to equal the first half of October for potting up all maiden plants from the open ground. At the time stated the new root fibres are most active, and the plants quickly take to the fresh soil. Even where the plants cannot be immediately potted it were better to lift them and heel them in, so that the formation of the new root fibres is retarded.
Hybrid Perpetuals are best potted annually at about the same period, whilst Teas and Hybrid Teas, being more continuous in shoot and root production, and being required for autumn and winter work, should be repotted or topdressed as required in August or September. Good loam, with well-decayed horse dung and a little blood and bone manure, is all that the Rose requires. Highly concentrated manures in the hands of the inexperienced may be a source of considerable danger, and are not to be trifled with.