In most seasons a different form of chicon development is observed in the early OK Belgian endive varieties forced from the beginning of January onwards. The cold storage of the roots results in a degree of vernalisation such that the chicons developed in the first 10 days exhibit a tendency to open growth. This vernalisation results in the ready development of the pith.
Forcing is no longer required, and the chicons merely need to be allowed to develop. Lower initial temperatures are sufficient, since the pith will develop at a suitable rate: a relatively high final temperature is required to promote tight chicons.

Take care to avoid dehydration

Optimum storage conditions are extremely important. Make sure that the roots forced after the New Year are frozen in December (-2 °C), and make sure that the roots are thoroughly moist before freezing.
Roots with more substantial leaf ripening lifted later in the season are more vulnerable to dehydration. Chicory roots with a higher concentration of solids (>25%) and relatively bare crowns are extremely vulnerable to dehydration: even slight dehydration of these roots results in accelerated exhaustion and coarser chicons. Make sure that the roots in kept in chilled storage remain suitably moist.

Calcium chloride

You can take a number of measures to combat the coarser chicon symptoms.
A successful treatment, used for many decades, is based on immersion in a calcium chloride solution to alleviate the initial stages of exhaustion and a water deficit in the roots. Moreover, the addition of calcium chloride results in smoother, firmer, somewhat shorter chicons. More information is given in using calcium chloride.
In recent years an increasing number of forcers have switched to immersion in a calcium chloride solution. Immerse the chicory roots in water within 24 hours of setting. If so required, reduce the quantity of calcium chloride sprayed onto the root crowns to 30-50 g/l/m2, and moisten the roots during forcing.

Adjust the temperature schedule

Chicosem recommends the use of a flatter schedule from the beginning of January, i.e. begin with a lower temperature and don't reduce the watertemperature too much to the end of the forcing period to obtain a fairly flat temperature curve. In general, an initial water temperature of 17/18 °C will be sufficient in January (15/16 °C in February). Maintain the air temperature at 1-2 °C below the water temperature, and reduce the air velocity. If necessary, allow the air temperature to rise a little towards the end of the forcing period.
Reduce the concentration of ammonium in the nutrient schedule to maximum 1.8 mmol/l at the start of the forcing period. Reduce this level to 1.0 mmol/l during the second half of the forcing period.
Endeavour to complete the forcing phase within 21 days.