This section is from the book "Indoor Gardening", by Eben E. Rexford. Also available from Amazon: Indoor Gardening.
An old favorite, which no plant of modern introduction has been able to displace. It is a free bloomer. Its flowers are of varying shades of purple-blue and lavender. It is not a showy flower, on account of its subdued color, but it is a beautiful flower for all that. It has a most delightful fragrance. A small cluster of bloom will sweeten quite a large room.
It is easily grown from cuttings. Plants started in spring will grow to flowering size by the middle of summer, but I would advise keeping all buds picked off if you intend to make use of them during winter. Pinch the young plants back well from time to time to make them bushy. The more branches you have the more flowers you can expect.
This plant likes more heat than most plants. It must have plenty of sunshine. It has very fine roots, therefore it must be watered freely, and with great regularity. Allow the soil to become dry and the plant will almost always drop its leaves. The same thing will happen if it is exposed to coal-gas. Give it a soil half loam, half turfy matter, with considerable sand worked into it.
Drain the pots well. Use considerable fertilizer when the plant comes into bloom. Make cuttings of the old plants in spring, for use in the outdoor garden later on.
Plants of shrubby habit, blooming freely and continuously throughout the entire summer, and again in winter if cut back and made to renew themselves. Colors range from pure white, through pink to red, yellow, and orange. Flowers borne in clusters, all over the plant. Can be made to grow to large size, but this is not desirable unless you have a room solely for flowers, where large plants will not be crowded. Does well in any good soil. Is seldom attacked by insects. Grows readily from cuttings. Equally at home in a pot or in the garden.