This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
It is not often that one sees or hears of Celosias being grown except for the autumn decoration of plant-houses. It is the custom to sow seeds at a certain time; and I suppose we are determined to abide by the custom as religiously as if it were an offence to depart from it. I am not writing in depreciation of the value of Celosias as autumn-flowering plants - my desire is rather the contrary, for there is not a class of plants grown that are more useful or more worthy of cultivation, either for cut flowers or as decorative plants. It is only lately that I have been able to secure a strain of Celosias worth cultivating. I have grown as many "weeds" under the name of Celosias as most people; and it was only through the recommendation of a friend that I could be induced to attempt a resuscitation of their culture with anything like spirit. Even annuals require cultivation to make them grow well; but it really damps one's zeal, in cultivating plants from seed, when deceived in the quality of the article purchased.
Last year I resolved upon growing a few plants extra well, to come in for the conservatory in July; and by a miscalculation, and probably by a little neglect in shifting at the proper time, they were in full blow early in June. But they came in useful for a purpose I never thought of before - viz., for supplying cut flowers at a time when the principal show of spring-flowering plants was over, and when flowers of any class stand the box badly. They travel so well, and their beautiful feathery sprays, so rich in colour, are so well adapted for giving effect with other flowers, that I venture to recommend the idea of growing an early batch for this purpose to those who have not previously tried it, and who are, like ourselves, hard enough up at times to wind up the season like the "cut and come again" practice of more extensive establishments.
There is always a little dearth for flowers in June, before Roses and other outdoor flowers come in to assist in filling up the flower-basket.
About the first week in February will be a good time to sprinkle a few seeds over the surface of a pan, and cover them thinly with fine earth. Plunge in a bottom-heat of 85°; and when the seedlings are about an inch long, remove them to a shelf near the light, and keep them regularly supplied with water. When they gain a little strength and will bear handling, they should be pricked off into shallow pans filled with rich mould, which should be placed on the surface of the bed for a few days, where they can be covered with a handlight, or otherwise shaded, and where they will furnish themselves with bunches of fine healthy roots in the course of a few days. They should then be returned to a place near the light, and kept well watered and syringed till they are ready to be shifted into 3 or 4 inch pots. As they are plants of rapid growth, the time or size of the shift is not of great moment (only they must not be allowed to become potbound in a young state, or it will arrest growth and cause them to feather prematurely), but it will be as well to determine beforehand what size of pot the plants shall flower in, and gauge the shifting accordingly. 8-inch pots are quite large enough for all ordinary purposes, so that 4-inch pots will answer for the first potting, and will leave ample room for working in a good addition of fresh soil at the last potting.
The soil may consist of any rich compost that has been in use for growing Melons or Cucumbers, with an addition of rough leaf-mould. It should be warmed to the temperature of the house in which the plants have been growing; and if the weather is inclement, it is a good plan to take a portable potting-bench to the house in which the plants are, and have them potted off without incurring the risk of giving them a check. After potting, plunge them again into the bed for a few days, and withhold water, except what is applied through the medium of a syringe, to keep a steady growing atmosphere; and when the roots take hold of the fresh soil, water freely as before. The increase of roots, and the rapidity of growth under this treatment, will hasten the development of the plants in an incredibly short time; and when they are nicely-furnished plants, they can be lifted out of the plunging material, and set on the surface of the bed for a time, and afterwards toned off to a growing atmosphere of between 60° and 70°, where they will require more air, to harden them gradually to stand a lower temperature. At the last potting the size of pot may range from 6 to 8 inches in diameter.
Of course those that are shifted into the smallest-sized pot will show their feathery plumes first; so that by using pots of two different sizes, a succession can be secured from the same batch of plants.
The final shift being given, it will still be necessary to encourage growth (but in a somewhat lower temperature, as above suggested) till the pots are well filled with roots. I3y this time they will have made nice plants, and will require increased air and light, in order to bring out the beautiful and varied tints of colour which are characteristic of selected types of this well-known annual. They possess the additional advantage of bearing being retarded for weeks if necessary; and, taken altogether, they are about the most simple plants to cultivate, and the most elegant to look at, that we possess.