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.
These large-leaved plants are derived from G. arachnoidea, C. corymbosa, and C. crenatiflora - all natives of Chili. The progeny of these plants are remarkable for their large and gorgeously coloured and elegantly blotched flowers of various shades. They are all raised from seeds and require the protection of a greenhouse or frame throughout the year. The seeds are sown in rich, sandy, and well drained soil in May and June in the same way as those of Begonias and Gloxinias, but in a temperature varying from 60° F. by night to 65° to 70° F. by day. If the seed pots or pans are covered with a sheet of glass, moisture is maintained overhead, and the young plants appear in less than a fortnight. When the second true leaf has developed the seedlings are pricked off about 1 in. apart in a compost of 3 parts leaf soil, 1 part rich loam, and 1 part sand. They are kept shaded and close for a few days till established. In about a month they will be large enough for 2½ - in. pots, and as these become full of roots, the plants are again transferred to 5-in. or 6-in. pots. About March - that is nine or ten months from the time of sowing the seed - the final potting takes place. The compost preferred by specialists on this occasion consists of 3 parts rich loam, 1 part leaf mould, and a good sprinkling of rough powdered charcoal and crushed oyster shell or a little mortar rubble. Failing this a little basic slag will be found excellent. Throughout the growing period, the main points to attend to are careful watering, sprinkling overhead on all warm genial days, shading from strong sunshine, fumigating if necessary for Greenfly, and keeping a watch for slugs, which are sometimes very troublesome. When the plants are coming into flower, weak liquid manure may be given occasionally, but over-watering must be guarded against (fig. 271).
Fig. 271. - Herbaceous Calceolaria.