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.
A very large genus of annuals, biennials, and perennials of varying size and habit. Very little trade is done in the annual species, but a little seed of G. macrostyla, C. drabcefolia, G. Erinus, and G. punctata is sometimes sold. The first-named is the best, having large cup-shaped purple flowers conspicuously veined with violet.
Besides the above species, nurserymen do a flourishing trade with lovers of rock gardens and flower gardens generally, in many other species and varieties of Campanula specially adapted for those purposes. Among the dwarfer growing varieties for rock gardens may be mentioned: abietina, 9-15 in., purple red or pale blue, May to July; Allioni, 4 in., blue (rarely white); alpina, 3-9 in., deep blue; coespitosa, 4-6 in., deep blue (with a white variety); carpatica, 9-12 in., white and lilac; cenisia, 3-6 in., blue; Elatines, 3 in., trailing, purple; garganica, 3-6 in., blue; muralis or Port-enschlagiana, 3 in., pale purple; pulla, 3-6 in., violet blue; pusilla, 4-6 in., blue; Raineri, 3 in., blue; rotundifolia, the Harebell, 6-12 in., blue, and white; turbinata, 2-3 in., blue, also with a pure white variety; Waldsteiniana, 3-6 in., violet blue; Warleyi, 6 in., bright purple, with two corollas; Zoysi, 3 in., pale blue. These all flower during the summer months, from May to August and September, and in most cases are easily raised from seed, division, or cuttings in spring or autumn.
Fig. 186. - Callistephus hortensis.
The following Campanulas are grown and sold as general border or rock plants, viz. alliarioefolia, 1½ ft., white; glomerata, 1-2 ft., blue, with a white and a double-flowered variety; lactiflora, 2-6 ft., white; latifolia, 3-6 ft., blue, and white varieties; mirabilis, 1-2 ft., blue; nobilis (or punctata), 1-2 ft., violet, and whitish; rapunculoides, 2-4 ft.; Rapunculus, 2-3 ft.; rhomboidalis, 1-2 ft.; Trachelium, 2-3 ft., all with blue flowers.
In addition, C. pyramidalis is a biennial species largely grown for greenhouse decoration. It grows 4-6 ft. high, and has white and blue forms. The seeds are sown one year to produce plants for flowering the next. They realize from 8s. to 10s. per 100 in the young stage.