This plant, which is probably native to East India, is produced more extensively for European than for American markets. It is not generally grown in the home gardens of the United States. In the cities it is consumed mainly by the foreign population, although the general demand is increasing. It is an annual, and, being hardy to frost, it is grown mainly as a late fall or early winter crop and used principally for salad purposes. The cut, curled and frilled leaves are very ornamental when fully blanched and are frequently used for garnishing, and for flavoring soups; the young, tender leaves are also excellent when cooked as greens.
There are two general classes; namely, the curled or fringe-leaved and the broad-leaved varieties. The former is highly ornamental and much more largely grown than the other. Giant Fringed, Green Curled Winter and White Curled are the most popular sorts of the first class. Broad-leaved Batavian is the best representative of the second class, which is used mainly in stews and soups.
Any rich, moist soil adapted to lettuce will grow a good crop of endive. Rapid growth is important to procure tender, succulent leaves. The plant foods should be quickly available, and nitrate of soda should be used as a top-dressing whenever the plants indicate the need of nitrogen.
Although grown mainly for fall and early winter markets, an early summer crop may be produced by starting the plants under glass or by sowing in the open as soon as the ground can be prepared. For the fall crop the seed should be sown in July or August, depending upon climatic conditions. The plants require 40 to 50 days to reach marketable size. They make the most satisfactory growth during the cool fall weather. The seedlings may be started in specially prepared beds, and transplanted when of the proper size, or the seed may be sown where the plants are to mature. Whichever method is used 1 foot apart each way provides sufficient space for the full development of the plants. Some growers prefer to thin to only 6 or 8 inches.
Unless the leaves are wanted for soups, stews or greens they should be thoroughly blanched. This whitening process is necessary to reduce the bitterness and to render them more tender; it also improves the appearance of the leaves when wanted for garnishing.
Blanching requires 10 to 20 days or longer in cool weather. Any means which will exclude the light from the central leaves and keep the hearts dry to prevent rotting will be effective; the leaves should always be dry when blanching is started. The plants should not be blanched faster than used, because of the danger of the white tender leaves decaying when fully blanched.
The most common method employed is to tie the tops together with raffia or coarse twine. Covering with boards, tile, flower pots (with the drainage holes closed) or other devices will serve the purpose. Soil is also used sometimes, banking as for celery. Leaves or straw may be thrown over the plants late in the fall when it is desired to leave them in the field until the weather is more severe. Many growers lift the plants with some earth clinging to the roots and reset close together in cool cellars, pits or cold frames, shading them when blanching is desired. Endive may be preserved in this manner until midwinter.