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.
This favorite flower has of late years been brought to great perfection, and blooms exhibited in April last before the Pennsylvania Horticultural Society, might well vie with the finest English varieties, such as we often see pictured in the London Horticultural publications.
Much depends, however, upon the cultivation and season; several articles have recently appeared in the Horticulturist on their cultivation, but as they all differ somewhat from my own practice, it may not be uninteresting to some of your numerous readers to briefly give my method.
The best season for sowing the seed is about the 20th of September, making another sowing about a month later for a succession. Where plants are desired for blooming in the greenhouse during the winter, the seed must be sown in August. Sow the seed carefully in shallow boxes or seed-pans; the soil should be rather light and sandy. Keep the boxes in a cold frame or greenhouse, shading them from a hot sun. Be careful not to over-water, as the young plants are very liable to damp off. As soon as the plants are large enough to handle, they should be picked out of the seed-pans or boxes into other boxes, setting them about two inches apart each way. They can remain in a cool greenhouse or sheltered frame until about the first of February. They are then potted into four-inch pots, and kept upon the front stage of a greenhouse until they are sufficiently established, and the weather becomes mild enough to remove them into cold frames, where they should be protected from the cold with sash, observing to give them plenty of air, when the weather is pleasant. Where extra fine flowers are desired, it will be necessary to give them another shift into five or six-inch pots.
Two things are absolutely necessary in growing fine Pansies: first, to secure good, reliable seed, without which all your efforts will be unavailing; the other is, to give them the very best of cultivation. The soil to grow them in ,must be a rich compost of decomposed cow manure, leaf mould, and good garden loam or sods, well rotted. The plants, when coming into bloom, must be frequently watered with clear liquid manure, which can be made of a solution of Peruvian guano, or stable manure with water, well stirred up, and allowed to settle before using. Observe not to make it too strong; as a weak solution frequently applied will be the most beneficial by the above means. I have my Pansies in their greatest perfection during the months of April, May, and June; and where great care is taken in shading, watering, etc., they may be continued much longer. Where plants are desired for planting out of doors, and later blooming, they can be left in the boxes, and set out early in the spring in well manured and deep dug ground, setting the plants about one foot apart each way.
Many persons defer the sowing of Pansy seed until spring, and of consequence fail to produce good flowers, as the hot sun of June and July will soon cause the flowers to dwindle to one half their former size.