Sow in pots in a propagator, at 15-18C (59-65F), in March or in a cold frame, sowing seeds thinly.
Germination can be erratic.
Ideally, grow on in a frost-free glasshouse or cold frame, although good results are possible on a bright windowsill.
Transfer single seedlings to individual small pots as soon as they can be handled. Maintain temperatures of 15-18C (60-65F), as excessive cold can lead to premature flowering (bolting).
‘Harden off’ before transplanting young plants at the end of May or early June, once the danger of frost has passed. They are very sensitive to cold weather at this stage, so planting out should be delayed if the weather is cold.
Plant 30-38cm (12-15in) apart in and between rows; plant with the crown at soil level. Covering plants with fleece will enhance their growth and also reduces the chances of the plants bolting.
The young plants are planted out at the end of May/early June. Plant out 30cm (12in) apart in rows 40-45cm (16-18in) apart making sure not to bury the crown - the stem base should be at soil level.
Celeriac is a moisture-loving plant that needs fertile, organic rich, moisture retentive soil and prefers full sun. Keep the soil constantly moist – it should never be allowed to dry out. Water before the onset of drought; mulching helps, too. Keep the ground weed free.
As the plants mature, remove the outer leaves as they fall horizontal, to expose the crown and allow it to develop. Remove side shoots if they appear.
Harvest from October to the following March.
Leave in the ground until required, and cover with a thick layer of bracken or straw during the cold winter months to prevent the ground from freezing.
Alternatively, lift mature roots and transplant in spare ground in early spring, so the ground is available for sowing in spring or store in potting compost in doors with the leaves twisted off.
The knobbly roots can be grated and added to salads, or chopped and fried as chips (excellent with steak or game). In fact, they can be cooked in any way that potatoes and parsnips. The leaves can be used in salads or dried for cooking.
'Monarch’ AGM: A smooth skinned variety with succulent flesh.
‘Alabaster’: High yielding with good resistance to running to seed (bolting)
‘Prinz’: Has aromatic flesh and is resistant to leaf disease and ‘bolting’
Slugs: Leaves and soft growth are eaten.
Remedy: use slug traps, biological control nematodes, encourage natural predators, go slug picking on damp evenings. Use environmentally friendly slug pellets, based on ferric phosphate.
Read more information on slugs
Celery leaf miner: Small larvae tunnel through the leaves, leaving brown blisters. Severe attacks check growth.
Remedy: Grow under horticultural fleece or mesh. Pinch out affected leaves; do not plant seedlings with affected leaves. Parsnips can also be affected. No insecticides are available.
Celery leaf spot: Brown spots appear first on older leaves, spreading to younger leaves.
Remedy: Use treated seed, rotate crops, spray with copper-based or Difenoconazole fungicide. Fish oil-based fungicides cab also be used.