Celeriac

Origin & history

The wild form of celery grows on salty coasts and salt meadows in Europe; in ancient Greece the foliage was woven into victors’ wreaths long before anyone ate the root. The bulbous form only appeared in the 16th and 17th centuries and was grown mainly in northern and central Europe — which is why English once called it “German celery”. Celeriac, stem celery and leaf celery are botanically the same species, just different varieties.

Varieties

Look for bolt-resistant varieties with smooth skin and few side roots — the more wrinkled and whiskery the bulb, the more of it ends up in the compost when you clean it. Varieties such as “Prinz” stay white when cooked, while older types go greyish. Because the pre-culture takes ten weeks and the seed is tiny, many people prefer to buy young plants; if you do, pick sturdy ones with a short, firm heart.

Care

Celeriac is a hungry crop with a high water demand — let the bed dry out in between and the bulb stays small and turns woody; mulch keeps the moisture in. A second dressing of compost in July pays off. From late August take off the outer, flat-lying leaves and cut away the roots on top of the bulb so it grows round and smooth — leave the heart alone, or you slow the swelling down.

What can go wrong

The classic mistake is planting out too early: a cool week below 10 °C after planting makes celeriac bolt in summer instead of forming a bulb. Brown leaf spots (Septoria) usually arrive with the seed and spread on wet foliage — space the plants widely, water at the base, take off affected leaves and keep a three to four year break. Bulbs that are hollow or brown inside point to heavily limed, too dry soil.

Harvest, storage & kitchen

Lift before hard frost — the bulb takes a light frost, a hard one makes it glassy. Twist off the foliage, trim the beard of roots and pack the bulbs in damp sand in a cool cellar, where they keep into spring. Be generous when peeling, the skin stays tough; cut surfaces go grey in the air, so mix grated celeriac with lemon straight away. Chopped fine, the leaves are the green in a soup.

Frequently asked questions

When do you plant celeriac out?

Between 10 May and early June, once nights no longer drop below 10 °C. To hit that, start the plants indoors from late February and allow about ten weeks. Set them out 40 cm apart in both directions.

Is celeriac winter hardy?

No. The bulb sits on top of the soil and goes glassy in harder frost — unlike parsnip or black salsify it cannot overwinter in the bed. The end of October is the cut-off, and from then on the crop keeps only in a cool dark cellar.

When is celeriac ready to harvest?

From mid-September, once the bulb is 8 to 12 cm across, and the whole row by the end of October at the latest. It puts on real size in those last weeks, so lift only what you need at a time.

Can celeriac be frozen?

Yes: peel it, cut it into cubes, blanch for two to three minutes, cool and freeze in portions — that keeps it usable for around eight months. Frozen raw it discolours grey and thaws out soft.