This section is from the book "Commercial Gardening Vol4", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
This perennial composite is a native of South Europe. It grows up to 6 ft. in height, and has large pinnate leaves, greyish-green above, almost white beneath. In some varieties there is a yellow or brown spine, often over 1/2 in. long, in the angle of the leaf divisions. The fleshy leaf stalks when blanched, as well as the thick fleshy main roots, are the edible portions. The best-known varieties are the Prickly Tours (fig. 501), the Ivory White, the Spanish, and the Artichoke-leaved or Puvis. Of these the Prickly Tours is considered the most valuable, notwithstanding the wicked spines on its leaves, which necessitate great care in working among the plants.
Cardoons like a deeply trenched and well-manured soil. They are always raised from seeds. These are sown in heat in April to have plants for the open air by the end of May or early in June, the seedlings being potted up singly when large enough to handle. In the open air the plants are placed in holes or trenches about 1 ft. deep, and from 4 to 5 ft. apart. The space between the rows are utilized for quick-growing crops like Radishes, Early Carrots, Lettuces, Dwarf Beans, Spinach, etc, which are taken off before the blanching process begins.
Fig. 501. - Prickly Tours Cardoon.
Blanching takes place in autumn. The stems are carefully gathered together by winding string round them. Straw bands are then tied round them to exclude the light, or soil may be banked up round them as for Celery. To blanch the stems thoroughly it is necessary to exclude the light from them for at least three weeks. They are then cut just below the surface of the ground, the withered leaves are detached, and the roots are trimmed up neatly.