This section is from the book "Commercial Gardening Vol2", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
The Shrubby Calceolarias - said to be descendants of the Chilian G. rugosa - are almost hardy in the milder parts of the kingdom, and during the summer months at least they are used in thousands for bedding-out purposes. Being dwarf, sturdy, and compact in habit, and not requiring any stakes, they are well suited for this work, especially as their pouch-like flowers of gorgeous yellow, crimson, or maroon, are produced with great freedom. The plants are raised from cuttings in September and October. Non-flowering well-ripened young shoots from the base of the old plants are preferred as cuttings. They are inserted in very sandy well-drained soil in cold frames. Here they pass the winter, receiving, however, plenty of light and as much air as possible, after being rooted, in genial weather. Sharp frost must be excluded by mats or other material. In February and March the young plants are carefully lifted and potted up singly into 3-in. or 5-in. pots. The tops are pinched out, and by keeping the plants close and shaded from strong sunshine for a few days they soon recover. They are watered when necessary and sprinkled overhead on genial days. The tops of the shoots may be dibbled into boxes of sandy soil as cuttings, and if kept warm and moist for a few weeks, either in a hotbed or close frame, they soon root, and make sturdy little plants the best of which may be transferred to 3-in. pots if necessary. A good trade, however, is done in box stuff as well as in pots. A compost of loam, leaf soil or well-rotted manure, sand, and a sprinkling of basic slag suits Calceolarias very well. They are somewhat subject to Greenfly under glass in spring, but this pest may be kept down by vaporizing, or fumigating, or by syringing the plants with a solution of quassia chips, soft soap, and nicotine. To maintain a gay appearance during the summer months the plants require copious supplies of water, especially when used in window-box decoration. Plants are often killed by a fungoid disease, probably Botrytis, and as there is no remedy it is best to have them pulled up and burned. Before planting afresh, the soil might be dressed with flowers of sulphur.
Amongst the most popular varieties of Shrubby Calceolarias are Golden Gem, Gaine's Yellow, aurea floribunda, and Prince of Orange amongst the yellows; Bijou, General Havelock, Firefly, Sultan, Sparkler, and Victoria amongst the deep crimson, bronzes, or maroons.
A Peruvian species - C. amplexicaulis - 1½-2 ft. high is often seen in public parks and gardens. It has beautiful soft lemon-yellow flowers. C. Burbidgei - a hybrid between G. Pavoni and G. fuchsiaefolia, is also an attractive plant, 2-4 ft. high, with soft yellow flowers, and with a loose habit. G. alba, with pure-white flowers, is a Chilian species, 3-4 ft. high. All these offer splendid scope to the hybridist.