Self- blanching celery does not need earthing up, but non-self- blanching celery is grown in a trench because it needs earthing up to make the stalks go white.
To grow the non-self-blanching celery:
In late May, plant celery seedlings into the trench, 12inches between plants in the row & 10 inches between rows
When plants are 8 inches high:
Keep earthing up every 3 weeks until the soil is up to the base of the leaves
Keep celery moist at all times, and water well when ever the soil dries out
The celery is lifted from the ground as required through autumn and winter.
Self blanching celery does not require growing in a trench.