About a month before the first chicons are required for the table, take out as many roots as you need; each root normally produces one chicon. For a continuous supply, lift a few roots every week or fortnight. Lifting all your roots at once will lead to a glut of; as it does not keep particularly well, successional forcing is a far better practice. Any container which is reasonably light proof will do, provided it is deep enough to take the roots comfortably. You can use barrels, large flowerpots, black plastic bags or wooden boxes. Fill them part way up with damp sand, moist peat, potting or light . Then put the roots in vertically, 5-7.5 cm (2-3”) apart, and fill up the container with the remaining compost until the crowns are about 2.5 cm (1”) below the surface. The problem of excluding light can be solved in three ways. The containers can be placed in an absolutely dark room or shed, in which case they will not need covering.
Alternatively, cover the containers with boxes, black plastic, sacking, or inverted pots to keep the light out, remembering to allow sufficient headroom for the developing chicons.
Lastly, you can cover the crowns with about 17.5 cm (7”) of additional peat, sand, or compost. Although it is a more tedious method, chicons which are forced through soil or other material tend to have more tightly packed heads than those growing without covering. The one exception is the new variety Normata, which will produce tight heads without being earthed up, although darkness is still essential.
You can also force chicons in the soil under the greenhouse staging. Use a dibber to make holes 5 cm (2”) apart. Fill the holes with water, and when it has drained away, put the roots in. Exclude light either by draping black plastic from the staging to the floor of the greenhouse, or by earthing up. Use 23 cm (9”) boards along the edge of the border to form a temporary retaining wall. Cover the planted roots with 17.5 cm (7”) of suitable material, and sprinkle it lightly with water.
The roots need a minimum temperature of 10°C (50°F) to start producing shoots. If the surface of the sand or compost looks bone dry any time during forcing, sprinkle it lightly with warm water, but be careful not to over-water.
Depending on the heat, chicons should be ready for cutting from a month to six weeks after the roots have been planted. Begin inspecting the containers or greenhouse border after a month. Chicons are best when about 15-20 cm (6-8”) long; those forced without earthing up will be about 12.5 cm (5”) above the soil. The spear-like tops of those being forced under sand or compost will be slightly below the surface; a small mound of disturbed soil will appear directly above them. This mound indicates that the chicons are ready for pulling, and it is pointless to leave them longer.
To harvest, pull up the root and cut off the chicon afterwards. The aim is to get a complete chicon, not one that disintegrates into separate leaves as soon as it is touched, so cut as close to the crown as possible.
A second, smaller crop of chicons may sometimes be taken by replacing the roots in the same container after cutting, but you will get far better results if you use fresh roots.