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.
I hope you will permit me to make a few remarks for the benefit of those of my own class that have no garden. To these I say, Make the best use you can of your windows. This is already being done quite extensively in the case of the more tasteful dwellings of many of the working classes; and to those who object to attempt anything of the kind on the ground of want of skill as cultivators, I say, A careful and regular attendance is much more requisite than a scientific knowledge, though both are very essential to the successful florist.
A few hints on the culture of Mignonette as a window-plant may be of service to those of my own class who are among the readers of this work. The end of April is the best time to sow the seed. As it is intended that the plant to be raised should last for a considerable time, it is essential to lay a good foundation in the preparation of the soil. It should be a rich compost; one-third cow-dung that is dry enough to crumble to small pieces, more than one-third of good mellow loam, and the remainder silver sand, with a handful of old lime-mortar dust, to keep the compost open. Having prepared the soil and provided the seed (that known as the large flowering Mignonette is the best), then take as many pots, from 3 to 4 inches in diameter, as will be required, place at the bottom of each for drainage a few small pieces of broken pots, and over that a little of the roughest of the soil; then fill up nearly to the top of the pot; place three seeds in the centre of each pot, cover them slightly with earth, press it down rather firmly, and place the pots in the window. In ten days the young plants should be pushing through the soil, and as soon as they appear above ground plenty of air should be given them.
When the weather is fine, the pots should be placed outside the window during the sunniest part of the day, and a gentle shower occasionally given them from a rose watering-pot if the weather be hot and dry; if dull, a slight watering the first thing in the morning will be found sufficient. When the plants are large enough, pull out the two weakest ones, and leave the strongest, as this is to form the future tree. As it makes growth, place a neat stick by the side of the plant, about a foot in length, tie it loosely to this stick with a piece of fine matting, and do so as it increases in height, and reaches the top of the stick, then replace it with a longer one, if a long stem be desired; that, however, is a matter of taste merely.
As soon as side-branches break forth from the stem of the plant, slip them back to the second eye; but avoid what some persons are apt to do who do not appear to value the leaves, cutting the side-branches back to the main stem. A naked, leafless trunk is scarcely in taste, therefore leave as many leaves about it as possible the first year, so that the stem may have a feathered appearance.
And now comes the winter, during which the plants may be kept pretty dry till they make young growth, when more than one-half of the side-spurs should be cut away, beginning at the bottom, and only taking off a pair at a time, and doing the same at intervals of a fortnight. During the first year no bloom should be permitted to appear on the trees; the second year they should be allowed to bear flowers after the middle of October, and all through the winter; but up to that time all flowering-buds should be plucked off as fast as they appear.
About midsummer shift the plants into a 5-inch pot, and give them another and rather larger shift about the end of July, but never shift the plants after August, as it would check them, and perhaps destroy all one's hopes of what they might do in the future.