This section is from the book "The Gardener V2", 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.
I send you the method by which I grow my Polyanthuses in beds. I take the soil out of the bed 18 inches deep, and I put a thick layer of old horse-dung at the bottom. Then I mix the soil from the bed with old turf, leaf-mould, and good sharp sand, well mixed together in equal proportions, and I put it on the horse-dung on the bed where the plants are to flower. I put the horse-dung at the bottom of the bed, because I find the plants always strike down to it, and they flower much stronger. The situation that I always find the best is a shady border under a hedge, where they are screened from the hot sun. The Polyanthus is often killed with red-spider: to avoid which, as soon as possible, I lift them from the frame with a good ball of earth, and take care not to break the young roots off them. I plant them 10 inches apart. When in flower, I shade them from the hot sun, and the flowers consequently keep fresh much longer. Crossing for seed should be done from 12 to 2 o'clock. Impregnation is more effectual when done at this time. The plants that I save seed from are those that I bloom in pots in a frame, and from which bees are kept.
The best-marked flowers, with the best tubes - such as Lord Lincoln, Beauty, George IV., Kingfisher, C. Allsebrook, and President - are good to breed from, as they seed freely. I am sure if any of my Polyanthus friends will try those sorts, they will find them excellent. I have myself 2000 plants of seedlings to flower this spring, and something like forty kinds to plant out to try again that were very promising last spring. Some of them I expect to be fine. To raise a good stock I make up a hotbed in my large frame and put 6 inches of leaf-mould in it. Twelve days after, when the heat has subsided, I take my plants up and divide them. The latter end of July is the best time for this operation. Take care that there are no old roots left to them, as they are often cankered, and do the plants no good. It does not matter if there be no roots to them at all, as they soon make new roots when put in heat. I give them a good soaking with water, and keep them close for about twelve or fourteen days; then I give a little air for a few days, afterwards I take the lights off altogether till the latter end of September, and then put the lights on for the winter. I generally sow my seed the first week of March in well-drained pans.
Fill the pan with leaf-mould and turf, and a little sand on the top. In this I sow my seed, just covering it over, and give it a good watering, and put it in the frame till it comes up. As soon as the young plants form rough leaves, I put them out of doors till the latter end of June, then I plant them in beds, where they remain till they flower. Inferior sorts I pull up as they flower. If any of my Polyanthus friends will send to me in April, I shall be glad to send them a box of flowers of named kinds, and some of my seedlings to look at.
[We have had so many inquiries about this beautiful old flower that we express a hope that the remarks of Mr Allsebrook may serve as an answer to these inquiries. - Ed].