Celeriac Growing Guide
Celeriac, looking like a pale, knobbly swede, is a tasty, extremely hardy crop for colder months. Its edible part is a swollen stem with a mild celery flavour, rich in nutrients, antioxidants, and fibre. It can be grated raw into winter salads, cooked and mashed like potato, added to stews and soups, or sliced and roasted.
This guidance applies to the crop in general. Individual varieties and local conditions can differ.
Planting information
Sow seeds indoors in early spring (March) in small pots or modular trays filled with peat-free seed compost. Cover the seeds with just a light sprinkling of compost. Place in a heated propagator at 15°C or cover with a clear plastic bag and keep in a warm location. Germination can be erratic and slow, taking up to three weeks. Once seedlings appear, move them to a bright windowsill, conservatory, or greenhouse where the temperature stays above 10°C to prevent premature flowering. Water seedlings regularly. Once large enough to handle, thin seedlings in trays to one per module and transfer those in pots into their own individual pot filled with peat-free multi-purpose compost and water well. Plant young celeriac plants (grown from seed indoors or bought as plug plants) outside in the ground once all danger of frost has passed, usually in late May or early June. Harden off plants gradually to acclimatise them to outdoor conditions. Space plants 30cm apart in rows 40-45cm apart, ensuring plenty of space and good air circulation. Take care not to bury the crown; the stem base should be at soil level. Water in well and cover with cloches or biodegradable fleece to improve growth and help keep plants warm, reducing the chances of bolting.
Harvesting information
Harvest celeriac from October through to the following March. It is hardy and can usually be left in the ground until required, developing a stronger flavour over time. Carefully ease individual plants out of the soil with a fork. In colder sites, spread a thick layer of straw around plants to prevent the soil from freezing. To prepare, remove the small roots and the often knobbly outer skin. Celeriac can grow quite large without turning woody. Excess can be blanched and frozen.
Storage information
If not harvested by spring, plants can be lifted and transplanted into spare ground or stored. To store, twist off the leaves, then place the celeriac in a container of peat-free potting compost or coir in a cool shed or garage. If you have heavy soil or the site is prone to winter waterlogging, dig up and store celeriac in late autumn. Excess can be blanched and frozen.