This section is from the book "Commercial Gardening Vol1", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
In commercial gardening enormous numbers of plants are disposed of each year from the open ground and from under glass, and as soon as one crop is finished, another, as a rule, is ready to take its place. To maintain the equilibrium it is obvious that in accordance with the disposal of the plants a corresponding number must be raised each year.
Crops are raised in various ways, viz.: From (1) seeds; (2) cuttings of stems, leaves, or roots; (3) layers; (4) runners; (5) suckers; (6) offsets; (7) bulbils; (8) division of the rootstocks; (9) budding; (10) grafting and inarching. The commercial grower naturally adopts the method of propagation that will produce him a saleable crop within the shortest possible period, although a particular crop may be raised by more than one method.
Although in a state of nature this is the natural means of reproducing plants, it is not always the best or most satisfactory under other conditions. A whole host of plants, however, are raised from seeds each year, and in this way the seed trade already referred to at p. 2 is kept well employed. Such plants as annuals and biennials are necessarily raised from seeds, because they cannot well be perpetuated in any other way, owing to the short time they live. All natural species that ripen seed in our climate, and many florists' flowers, may be raised from seed, and the young plants will reproduce all the features of their parents. In the case of many florists' flowers, however, like Begonias, Dahlias, Chrysanthemums, Carnations, Snapdragons, Pentstemons, Petunias, Gloxinias, and many others, special varieties are propagated by other means, as they are unlikely to come perfectly true if raised from seed. Variations may and do occur as the result of cross-fertilization by insect agency, and this is often sufficient to alter the character of the flowers. All choice varieties of fruit trees and roses are not raised from seeds, except in the first instance. Most vegetable crops, being of an annual or biennial nature, are raised from seeds. Great care, however, is taken by raisers to keep their stocks of special varieties quite pure and free from cross-fertilization with inferior strains. The plants to bear seeds are grown in places as far as possible from those of a similar nature, to prevent the pollen being carried from one to the other.
Seeds vary considerably in size, from almost dust-like grains to that of Peas, Beans, Acorns, and upwards, to Coconuts. They are borne either singly or severally in their pods or ovaries, some plants like Begonias, Poppies, Marrows, etc, having from 300 to 600 seeds or more in a pod, while there are several thousands in many orchids. Whatever the size may be, each seed is the result of an ovule having been fertilized by the contents of the pollen tube that penetrated the tissues of the pistil from the stigma downwards, as the result of the pollen grains germinating. In the case of Fern spores - which are popularly known as "seeds " - the process is quite different, and is explained in the article on Ferns in Vol. II.
Each seed, when thoroughly ripe, contains sufficient nourishment to start the young plantlet in life under favourable conditions, and the main object of the cultivator is to get the seed-leaves up to the light as soon as possible, so that they may be able to assimilate the carbonic acid gas from the atmosphere to develop further tissue. Some seeds germinate more quickly than others, and seeds of the same plant will germinate either quickly or slowly according as it is in a favourable temperature or not. Under the best conditions some seeds take a long time to germinate, often owing to the extreme hardness and thickness of their coats. Experience has proved, however, that hard-coated seeds will germinate readily as soon as they drop from the parent plant; but if kept for a few months, and then sown, a considerable time may elapse before they begin to sprout. For this reason seeds of Cannas, Nelumbiums, and many of the Leguminosae are often filed before being sown, to reduce the thickness of the hard bony coat surrounding the embryo plant within. It may be worth while to quote the following remarks of the late Herr Max Leichtlin, from the Gardener's Assistant: "If practicable, it would be best to sow all seeds of hardy plants at once when ripe; we only delay sowing for the sake of convenience, because we should, in the case of autumnal sowings, be obliged to house a very large number of pans and boxes of young plants too small to pass the winter outside. Hard-shelled seeds must be sown at once, also all seeds of hardy bulbous plants. If seeds of Colchicum be exposed to the air for a few days, not more than 5 per cent come up within a year, and the rest may take five years to germinate, whereas, sown as soon as the seed pod splits, 30 per cent will germinate in the first year. Delay sowing the seeds of Lilium, Fritillaria, Tulipa, etc, and you will lose from 20 to 80 per cent. Campanulas and Ostrowskya readily germinate when sown at once, but if sowing is deferred till spring the seeds will probably lie dormant for a year, if they do not perish altogether".
The following data as to the number of days taken by various seeds to germinate may be of interest. The night temperature was about 60° F., and the day temperature ranged from 65° to 70° F. Those marked with an asterisk (*) were sown in the open air.
SHOWING ELECTRIC SEED-CLEANING MACHINERY (James Carter & Co.).
SHOWING MACHINERY FOR FILLING SACKS WITH SEED.