Coldframe. A Coldframe is a simple, low structure, covered with glass or oiled paper or cloth, in which plants are grown without artificial heat. It differs from the hotbed in the fact that it has no bottom heat. The atmosphere in the Coldframe is warmer than that outside, because it is protected from the winds and because there is more or less of the sun’s heat stored up in the earth. For the details of construction of the Coldframe, [see Hotbed].
A Coldframe is ordinarily used for later work than the hotbed: that is, seeds may be sown in a Coldframe from two to three and sometimes four weeks in advance of their sowing in the open; whereas in a hotbed the seeds may be started from one to three months earlier than they may be out of doors. Coldframes are sometimes used for the wintering over of hardy plants which are started in the fall. For example, cabbage seed may be sown in September in a Coldframe and the young plants may be protected therein during the winter. If they are properly grown and hardened off, they will not be injured by the winter, even though they freeze. Lettuce and sometimes cauliflowers are carried over in the same way. Coldframes are also used to receive plants which have outgrown the hotbed and must be transplanted. Plants which need hardening off may also be transplanted from the hotbed into the Coldframe. The Coldframe in these cases is an intermediate stage between the hotbed and the open field.
Coleus. A well known foliage plant for pot culture or bedding. It was used very extensively at one time in ornamental bedding and ribbon borders, but owing to its being tender has lost in favor, and its place is largely taken by other plants. Cuttings root very readily. It may also be grown from seed, although the types have not become fixed, and a large number of differently marked plants may be had from the same packet. This would not be a drawback in the window-garden, unless a uniform effect is wished. Sow the seed in gentle heat in March. Make new plants from cuttings each year, and throw the old ones away.
Collards. This is a name given to a kind of kale, used when young as greens; also to young cabbages used in the same way. The seed of any early cabbage may be sown thickly in rows 18 inches apart, from early spring to late fall. The plants are cut off when 6 or 8 inches high and boiled as are other greens. The kale Collards is grown in the South, where cabbages fail to head. It grows to the height of 2 to 6 feet, furnishing a large quantity of leaves.
Collinsia. A hardy annual that should be sown in the fall, where wanted, if early flowers are desired. The flowers of all the varieties are showy, either in masses or planted in a border. Give them a position near the front, as the plants rarely exceed 18 inches in height.
Columbine. [See Aquilegia.]
Compost. [See Manure.]
Convolvulus. [See Morning-Glory.]
Coreopsis, or Calliopsis. Very showy hardy annuals, growing from 1 to 3 feet high, and covered throughout the season with a profusion of bloom. The colors range from lemon-yellow to dark velvety brown. Excellent for cutting, and very effective in mixed borders. They thrive in any garden soil if they have full sunlight. Sow where they are to grow, letting the plants stand 6-12 in. apart for mass effects.
Corn Salad. This is one of the earliest spring salad vegetables, coming into condition to use with spinach, and needing the same culture. Sown in the fall, and covered with straw or hay when cold weather sets in, it will start into rapid growth when the covering is removed in March or April. Or the seed may be sown in early spring, and plants will be fit to use in six or eight weeks. One packet of seed will suffice for a small family.