I only use about four plants to flavour my various juices. I buy the seedlings and let them grow. They take no care. They can get quite large easily a foot or more in diameter. By not blanching they stay green and have a strong flavour. Often I just use shoots or stems and seldom the whole plant. The flavour is contained in the leaves.
http://www.durgan.org/URL/?QPBLS 1 May 2013 Celery plants moved to outdoor garden
The celery plants were moved to the outdoor garden. They have a good root system.
http://www.durgan.org/URL/?AYQMX 16 April 2013 Celery
Four celery plants were purchased and moved to individual pots and placed in the greenhouse. The purpose is to leave them for about two weeks before planting in the outdoor garden. This makes very strong plants with a good root system, and the plants get a good start. These plants get about a foot or more in diameter. I don’t blanche them by hilling, but use them in their normal green state.