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.
Although results are not so quickly attainable with trees and shrubs as in some branches of nursery or market-garden work, yet once stocks are secured and a supply maintained by a properly organized scheme of propagation, there should be no difficulty in finding a market. The development of garden cities and suburbs, the increasing practice of planting trees in streets, and the growing desire shown by owners of gardens and pleasure grounds, small and great, to utilize either flowering or foliage trees and shrubs, are all indications of a demand that has to be met.
The scope and extent of operations by the would-be nurseryman will naturally be largely determined by the amount of land available and its situation. A site in the south of England, or on the coast, for instance, will enable many subjects to be propagated and grown out-of-doors throughout the year, whilst similar plants in a nursery farther north may require a glasshouse for propagating and protection during the winter. On the other hand, stock from northern parts has the reputation of greater hardihood than that grown farther south.
The best soil for a tree and shrub nursery is undoubtedly a good deep loam, somewhat inclined to a sandy nature rather than too stiff. Clay should be avoided. If a portion of the land is of a peaty nature, so much the better; it will serve excellently for what are termed "American" plants. At one time it was considered essential that peat should be present in the soil to grow Rhododendrons with success. This is not so; they thrive splendidly in loam without a trace of peat, and, what is of great importance to the nurseryman, they transplant successfully from loam to the ordinary soil of the average garden. This is more than can be said of those grown on peat. An open situation is preferable, and low-lying ground should, as a rule, be avoided.
A glasshouse - one or more - fitted with propagating cases and heated with hot-water pipes should be available. Frames for inserting cuttings and hardening off young stock from the propagating house will also be required. It is also advisable, indeed essential in the colder parts of the country, to set aside a portion of the most protected part of the nursery and divide it into sections by planting shelter hedges. Beech is excellent for this purpose, though, owing to its somewhat slow growth, the green oval-leaved Privet is frequently used instead. In these sections there should be planted the more tender subjects as they come from the frames. As they develop they should be transplanted to the more open part of the nursery, their place being taken by further batches of young "growing-on" stock.
A word as to transplanting in general. To ensure safe removal from the nursery to the customer's garden the tree or shrub must possess a good supply of fibrous roots. These can only be produced by regular transplanting in the nursery. No definite or fixed line can be laid down as to how frequent this should be, as much depends on the soil, the character of the plant, etc. Whilst very frequent transplanting would develop numerous roots, it would at the same time have a retarding effect on the growth. Experience will teach as to how often it is advisable to transplant; the point to bear in mind is, that it should not be neglected or overlooked.
Another point that requires attention is the method of cultivating trees for street and avenue planting. Too frequently they are grown in blocks - row after row, side by side. This is a mistake. Unless a tree has space, air, and light it cannot be expected to attain its proper development. The better way is to plant in single rows, these being, say, 15 or 20 yd. apart. The intervening ground may be occupied by dwarfer-growing shrubs.
Seeds require to be sown under glass or outside according to their hardiness or otherwise. Spring is usually the best time to sow. Outdoor grafting is usually done in March, and budding in July, when the sap is in full flow and the bark lifts readily for the ripened buds. Cuttings for outside are usually made and planted during the autumn, using well-ripened wood. Plants such as Privet, Poplars, Ribes, Weigela, Willows, and deciduous subjects in general should have the cuttings made at least 6 in. in length, firmly planted closely together in rows, not more than 1 in. of the top part of the cutting being above ground when planting is completed. Cuttings inserted in pots, boxes, or pans indoors are usually of a softer growth than one would plant outside, consequently they may be inserted at various periods during the growing season.
Layering is practised with many shrubs that are of dwarf growth. Some of the more common sorts of Rhododendrons are propagated in the same way.
Where grafting indoors is referred to, it must be understood to have reference to stocks that have already been established in pots, and may be carried out during autumn, winter, and spring. As a rule it is unnecessary to use wax for indoor grafting, though it is essential out-of-doors.