This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
Of all winter salad plants, there are none more useful than this. Lettuce may "bolt" or fail to heart, and Endive decay before the winter has well set in, but Chicory may be had daily from October to May. A batch of plants of it should be raised annually. Seed sown in drills I foot apart, in moderately rich ground, in April, will soon produce plants, which must be thinned out to 6 inches apart as soon as they are large enough to handle; and if the ground is kept free from weeds after this, good carrot-like roots will have been produced by September. Any number of them may be lifted from that time onwards; and if they are covered up with any kind of soil and placed in mushroom-house, cellar, or any other dark place where the temperature is from 50° to 60°, there will soon be produced as great a quantity of beautiful crisp blanched salad leaves as anybody could possibly desire to handle or eat.