Centaurea.—Bold-habited composites of showy character; common soil. C. babylonica, 5 to 7 ft., has winged stems, silvery leaves, and yellow flower-heads from June to September; C. montana, 3 ft., deep bright blue or white.
Centranthus.—Showy free-flowering plants, for rockwork, banks, or stony soil. C. ruber, 2 ft., branches and blooms freely all summer, and varies with rosy, or crimson, or white flowers. It clothes the chalk cuttings on some English railways with a sheet of colour in the blooming season.
Cheiranthus.—Pretty rock plants, for light stony soils. C. alpinus, 6 in., grows in dense tufts, and bears sulphur-yellow flowers in May. C. ochroleucus is similar in character.
Chionodoxa.—Charming dwarf hardy bulbous plants of the liliaceous order, blooming in the early spring in company with Scilla sibirica, and of equally easy cultivation. C. Luciliae, 6 in., has star-shaped flowers of a brilliant blue with a white centre. C. gigantea is the finest of the few known species. It blooms from February to April.
Chrysanthemum.—Apart from the florist’s varieties of C. indicum there are a few fine natural species. One of the best for the flower border is C. maximum and its varieties—all with beautiful white flowers having yellow centres. C. latifolium is also a fine species.
Colchicum.—Showy autumn-blooming bulbs (corms), with crocus-like flowers, all rosy-purple or white. C. speciosum, C. autumnale, single and double, C. byzantinum, and C. variegatum are all worth growing.
Convallaria.—C. majalis, the lily of the valley, a well-known sweet-scented favourite spring flower, growing freely in rich garden soil; its spikes, 6 to 9 in. high, of pretty white fragrant bells, are produced in May and June. Requires shady places, and plenty of old manure each autumn.
Coreopsis.—Effective composite plants, thriving in good garden soil. C. auriculata, 2 to 3 ft., has yellow and brown flowers in July and August; C. lanceolata, 2 to 3 ft., bright yellow, in August; next to the biennial C. grandiflora it is the best garden plant.
Corydalis.—Interesting and elegant plants, mostly tuberous, growing in good garden soil. C. bracteata, 9 in., has sulphur-coloured flowers in April, and C. nobilis, 1 ft., rich yellow, in May; C. solida, with purplish, and C. tuberosa, with white flowers, are pretty spring-flowering plants, 4 to 6 in. high. C. thalictrifolia, 1 ft., yellow, May to October.
Cyclamen.—Charming tuberous-rooted plants of dwarf habit, suitable for sheltered rockeries, and growing in light gritty soil. C. europaeum, reddish-purple, flowers in summer, and C. hederae-folium in autumn.