This section is from the book "The Standard Cyclopedia Of Horticulture Vol2", by L. H. Bailey. See also: Western Garden Book: More than 8,000 Plants - The Right Plants for Your Climate - Tips from Western Garden Experts.
(Latin, little bell, from the shape of the corolla in some species). Campanulaceae. Bell-flower. Harebell. Bluebell. A large group of attractively flowering herbs, containing some of the most popular garden plants, especially of hardy herbaceous perennials.
Annual, biennial or perennial, mostly the last, often small and tufted: root-leaves usually larger than the stem - leaves, and often of different shape and more or less transitory: flowers blue, violet or white, sometimes yellow; calyx 5-fid; corolla 5-lobed or 5-fid; stamens 5, free; filaments wide at the base, membranaceous; stigmas 3 or 5, filiform: caps. 3-5-valved, dehiscing on the sides or (as in Fig. 762) at the base by 3-5 small valves; seeds ovate, complanate or ovoid. - Probably 250 species, nearly all in the northern hemisphere with the center of distribution in the Medit. region; about a dozen species are N. American. The species mostly inhabit swamps or moist ground, or alpine and boreal regions. Allied genera of garden value are Adenophora, Jasione, Lightfootia, Michauxia, Ostrowskia, Phyteuma, Platycodon, Specularia, Symphyandra, Trachelium, and Wahlenbergia, in which genera many species originally described as campanulas may be sought. Of these, perhaps the two best known cases are Platycodon grandiflorum, the "balloon flower," with its characteristic inflated buds, dark green, glossy, leathery leaves; and Specularia Speculum (C. Speculum), "Venus' looking-glass," a pretty annual, which grows in the grain fields of S. Eu., and is cult, for its violet flowers with a white eye.
The calyx-tube of Specularia is relatively much longer than in any campanula. The most prominent campanulas now in cult, seem to be the forms of C. Medium, C. carpat-ica, C. persicifolia, C. pyramidalis, C. punctata, C. pusilla (caespitosa), C. rotundifolia.
Botanically, campanulas fall into two important groups, based on the presence or absence of calyx appendages. The subgenus Medium has the appendages, and Eucodon lacks them. These appendages are often small and disguised. The genus may also be thrown into two broad groups based on the dehiscence, -the subgenus Medium with capsule opening near the base, and Rapunculus with the openings near the top. For the horticulturist, the most serviceable classification is based on the use that he makes of the plants, -whether as a garden vegetable, as border plants, or as rock-garden or alpine subjects; and this is the division attempted here. In cultivation, campanulas tend to become taller and more robust, less hairy, more branched, and more floriferous. Blue is the prevailing color in the genus. A very few have white or yellowish flowers, with no blue or violet forms. Any blue or violet-flowered form is likely to have white varieties, and double and semi-double forms are common in three or four of the most popular species. All flowers tend to become larger and more numerous on a stem. In cultivation, the three-celled species are likely to have five stigmas instead of three, and five-celled capsules, often along with normally constructed flowers on the same plant.
The height is the most variable feature of all, and in the scheme below C. carpatica, C. punctata and forms of C. glomerata especially will seem wrongly placed to many. But the characters used by botanists are well-nigh useless to the gardener, and nothing but a distinction of height can bring out the two important cultural groups of campanulas. For a recent garden monography of dwarf campanulas, see Correvon, "The Garden," 59 (1901) pp. 276, 450; 60, pp. 51, 64, 111, 161, 218.
Fig. 762. Capsule of Campanula with basal dehiscence.