Celeriac: Sowing, planting and harvest calendar

Sow celeriac under cover in early spring, following the packet and your climate. Use small pots or modular trays with drainage holes and seed compost. Scatter the small seeds on the surface; do not bury them 1 cm deep. If directed on the packet, cover them only with a very fine layer of compost.

Maintain consistent moisture without waterlogging the compost and keep the seeds in a bright place at a temperature suited to germination. Emergence can be slow and uneven. After germination, protect young plants from cold, thin or prick out into pots once large enough to handle, then harden them off before planting in the vegetable garden.

A temperature around 15°C suits the start of germination; once the seedlings appear, keep them above 10°C to reduce the risk of later bolting caused by cold. A clear cover can hold moisture before germination, but ventilate and gradually remove it as the shoots appear. Handle small seedlings by a leaf rather than their fragile stems. Record the variety and sowing date to follow this slow crop without repeatedly sowing in the same place before the original seeds have had enough time to germinate.

Celeriac has a long growing season and young plants are sensitive to cold. In cool climates, late outdoor sowing may not allow enough time to form a good swollen base: favour sowing under cover followed by transplanting. Consider direct sowing only if the variety and length of your season allow it, following the packet.

Prepare a fine, weed-free seedbed that retains moisture without becoming waterlogged. Sow very shallowly, with only a fine covering if directed. Water gently and do not let the surface dry out during emergence. Then thin to the final spacing recommended for the variety, distinguishing sowing distance from plant spacing. Watch for pests and leaf spots and identify the problem before treatment.

Compare the variety's time to maturity with the growing season still available before setting aside a bed for this method. Label the rows so you do not hoe over them while waiting for germination. Use a fine watering rose to avoid moving seeds that are almost on the surface. Do not try to compensate for slow germination by keeping a puddle over the row. When thinning, carefully remove the extra seedlings to preserve the roots of those left behind and give every remaining plant its final growing space.

Gradually harden off young plants, then plant out after frost when the weather is mild enough. Choose fertile soil that retains moisture without becoming waterlogged, in sun or light shade.

Space plants about 30 cm apart, with 40–45 cm between rows, depending on the variety. Keep the base at soil level without burying the crown. Water after planting.

Prepare the ground beforehand by removing competing weeds and incorporating well-rotted compost where needed. Moisten the root balls before removing the plants and make holes wide enough to take them without squeezing the roots. Support each root ball as it leaves the module, without pulling on leaves or stems. Bring the soil back around it and lightly firm with your hands before watering.

Check the planting depth afterwards: settling soil must not cover the heart. If you use fleece or a cloche during establishment, check moisture underneath and ventilate in mild weather. During the first few days, check the small root ball itself, which can dry out even if neighbouring soil looks damp. Keep enough room between plants to water and tend them without crushing their leaves.

Harvest when the swollen base reaches a usable size, usually in autumn depending on the variety and climate. Carefully lift the plant with a garden fork instead of pulling on the stalks.

In mild climates, harvesting can continue into winter if soil conditions allow. In waterlogged soil or before prolonged freezing, lift the plants and keep sound specimens in a cool place. Remove the leaves for storage and check their condition regularly.

Choose plants whose swollen bases are firm and large enough for your needs rather than waiting for one fixed date. Insert the fork beside the roots, then lift gradually to avoid puncturing the edible part. Gently shake off loose soil and separate damaged plants for prompt use if they are otherwise sound.

For a small kitchen harvest, take only the plants you need and leave the others to keep growing when conditions allow. Do not force tools into frozen ground: take a few plants ahead of a forecast freezing spell instead. Store only intact bases without soft patches or signs of rot. Arrange them so you can inspect their condition and promptly remove any that deteriorate. A damaged base should not be treated as suitable for long storage merely because it is still firm on harvest day.