Growing Celery has traditionally been seen as a labour-intensive task with trenches and blanching to achieve the long pale stems. There are numerous self blanching varieties such as 'Tall Utah' which make this more straightforward, although possibly resulting in a little less taste - it's worth giving both approaches a try.
Soil and Aspect
There are two methods of soil preparation: the trench method and that for self-blanching varieties.
For trench celery, in Autumn, dig out a trench in a sunny site 40cm wide and 30cm deep and add a layer of well rotted manure to the base. Back fill with soil and leave to settle over winter.
Self blanching Celery is planted in blocks rather than rows - dig over the site in Autumn and regularly incorporate plenty of well rotted manure and garden compost over winter.
Trench varieties are best started off under glass in Rootrainers in early Spring at a temperature of around 15c. Harden off under cloches two weeks before planting out 30 cm apart in rows in early Summer.
Self blanching Celery is started off under glass in the same way and hardened off before planting out more closely, in blocks, 20cm apart to help with the blanching.
Water thoroughly in dry periods and feed with a liquid feed every two weeks. When trench celery varieties reach 30cm earth up over part of the stems to exclude light. Repeat this at three week intervals until the soil is up to the lower leaves. An alternative to earthing up is to wrap cardboard around the stems.
For self-blanching celery, place straw around the outside of the block to reduce light on the plants.
Harvesting and storage
Trench celery is ready for harvesting in the autumn and onwards into early winter. Harvest as needed but remember that the first frosts will enhance the flavour. Cover plants in the winter with Easy Fleece Tunnel or Lantern Cloche and leave in the ground - Self blanching varieties should be lifted in the Autumn.
Pests and diseases
Slugs, snails, Celery Fly and Carrot Fly can all be a problem as can diseases such as Celery heart rot - effected plants should be destroyed and not added to the compost heap. You can avoid split stems by ensuring that you water regularly.