This section is from the book "Commercial Gardening Vol2", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
In growing hardy and half-hardy plants for sale the market gardener or nurseryman is guided by business instincts as to what will pay best, and not by sentiment. He crops his ground to the best advantage, planting in long straight rows when possible, to economize space, and so that he may have plants of any particular crop under his hand in bulk when he wishes to lift them. He cannot waste time running from one place to another for an odd plant, nor can he afford to waste space on any plant that will not sell fairly quickly, no matter how beautiful it may be in his own estimation. There is no attempt at landscape effect, the main object in view being to grow the plants as quickly as possible and sell them at the best price. For many kinds of hardy plants ordinary garden soil is quite good enough, and the more deeply it is cultivated, and the better manured, the better the results. In these days of keen competition, when plant growing has become a fashion with many more or less wealthy people, the man who produces the finest plants at a reasonable rate is the one who takes the lion's share of the receipts; while he who thinks that the old slovenly methods of his great-grandfather's days are quite good enough for modern cultural work must be content with prices that scarcely enable him to live.
For the cultivation of alpine and rock plants the ordinary soil of the garden may not be suitable, and it is generally more convenient for selling purposes to grow most of these plants in pots, and often in frames instead of planting them out. Supplies of peat, loam, sand, and leaf mould are therefore essential to the grower of special classes of plants, and it is not unnatural that he should look for higher prices for his labour and his produce. While it is not necessary to refer in detail to more or less scarce plants, those of the highest commercial value are more fully dealt with in this section. It is possible, however, that the rare plant of to-day may be the popular one of to-morrow.