This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
For raising common kinds, to withstand the winter in the flower garden, it is easy enough to procure seed; but to raise a first-class flower, such as should be considered sufficiently choice to repay by its extra beauty the extra care usually bestowed upon the improved varieties, is quite another thing. During our thirty years' experience, we have never seen one first-rate variety raised from ordinary seed. We would not be understood to say that seed purchased at seed stores is not worth all that is paid for it; in many cases, when the seed is fresh, it is; but if any one purchase with an idea of procuring such seed as will produce first-class varieties, he will most assuredly be doomed to disappointment. What, then, is to be done? The only way is to procure a few good standard kinds, and keep them apart from all the Primula family, as far as circumstances will admit. If others are growing near by, place the best kinds under a muslin shade during the blooming season, being careful that no winged insects find their way through the frame to the flowers, or all your care may end in disappoint-ment.
As to the most proper time for sowing the seed, I would advise September as the most suitable. The soil should be light and sandy, with a small portion of very rotten cow-dung, not less than from two to four years old. The seed pans should be well washed and dried before using. After having placed a sufficient quantity of drainage, (from one to three inches,) fill in to within one inch of the top with the compost, pressing it down rather closely. Upon this sow the seed evenly, but not thickly. Sift over it soil, through a fine sieve, to the depth of about the sixteenth part of an inch. After a gentle watering through a fine rose, remove the pans to a cool frame, placing a flat piece of glass over them. Keep the soil in that happy medium between wet and dry, when, if the soil be good, it will germinate in about six weeks. It is an old but excellent plan of the Dutch and French florists, in watering seeds and young plants of their favorite flowers, to use a hard clothes brush, dipping it into milk-warm water, and drawing the hand briskly up and down; by this means there is a beautiful vapor, which waters without washing up the seed or young plants.
As soon as the plants make their appearance, be careful to admit air by degrees, in order to render them hardy. When they have made about four leaves, remove them into seed pans or boxes, planting them about one inch apart, in the same kind of soil as recommended for the seed. Place them in a cool, dry place in a frame, where they may remain until the leaves touch each other, when they must be repotted singly into pots about three inches in diameter, in a soil composed of about equal parts of loam, peat, and very rotten leaf mold, with about one eighth of rotten cow-dung, (from three to four years old,) and sharp river sand. Place them again in the cold frame, where they may remain, well protected from severe frosts, until the following March, when they will require repotting into pots five inches in diameter, using one inch of drainage in the bottom of the pots, with the same compost as recommended for the first potting. As soon as they flower, which, under ordinary circumstances, will be about April, let all of them possessing good properties be selected, and named or numbered, and afterwards receive the same attention as directed for full grown plants.
Be careful not to turn out any of the plants which have not flowered, as it not unfrequently happens that the weaker plants prove to be the most beautiful varieties.