This section is from the book "Indoor Gardening", by Eben E. Rexford. Also available from Amazon: Indoor Gardening.
This plant deserves a place in every collection, for three reasons: It is of the easiest culture-it is an almost constant bloomer-and its flowers are very beautiful. In shape they are very much like those of the Phlox, but with narrower petals. They are borne in loose clusters, at the tips of the branches. In color they are a soft, delicate blue-an exceedingly rare shade among flowers, and especially so among house-plants.
This plant requires about the same soil as that given the Geranium, and about the same amount of water. It is of slender habit, and must be well supported when allowed to grow to suit itself. It can be made quite bushy by repeated pinching back, but is never as effective when trained in that way as when allowed to grow up the window. Its flowers are borne on new growth. As soon as the first cluster on a branch has developed, cut that branch back at least one half. Side-branches will be thrown out below, and these, in turn, will bear flowers. Feed well, in order to keep the plant producing new wood. The foliage of it is sparse and unattractive, but what it lacks in this respect it fully makes up in the beauty of its blossoms.
Once a year cut the old plant back very sharply, and force it to renew itself. Do this during the latter part of summer.