This section is from the book "The American Garden Vol. XI", by L. H. Bailey. Also available from Amazon: American Horticultural Society A to Z Encyclopedia of Garden Plants.
When we first tried this plant it was very much inclined to throw up long-jointed shoots and at flowering time the leaves turned yellow and dropped, leaving bare stems with only a tuft of leaves at top. Last spring we decided to try a new plan of growing it. When it had done flowering, we cut back all the shoots to about four or five inches and allowed the plants to remain in the same pots in which they had flowered. The object of this treatment was to obtain a larger number of shoots and a slow growth, which would give short-jointed wood. We kept them pinched back and sufficiently crowded for pot room to continue this style of growth all summer, and when the weather required them to be removed to the greenhouse in autumn, we gave them pots two sizes larger and a very rich compost, and the result has been fully satisfactory. They are now (middle of December) full of buds and bloom. the foliage full and dark green, and the flowers are much deeper colored than they have previously been. If allowed plenty of room while growing through the summer they must have correspondingly large pots to flower in or they will become so filled with roots as to need watering largely and often, and if neglected at all will shed their leaves. - Wm. F. Bassett.
 
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