Many European and Asian kitchens have long appreciated its crispness and flavour. With a little preparation, this extremely useful vegetable moves easily from garden to kitchen, it can be combined with other root vegetables, added to soups or used in place of mashed potatoes and adds a delicate flavour when used raw in salads.
Although a close relative of celery, this lesser-known kin is far easier to grow and like most autumn and winter root vegetables, it is a great keeper and will remain in good condition for four to six months in a cellar or refrigerator.
Celeriac is crisp and delicious, and it keeps all winter, but it is definitely not a looker. Once you’ve grown it and tasted its exquisite flavour and texture, however, you’ll realise that ugly is only skin deep.
Position: An important factor in growing fine-textured celeriac is proper soil conditions. The ancestor of both celery and celeriac grew in marshy areas, and the closer your soil is to a rich and moist environment, the happier your celeriac will be. A generous amount of compost or rotted manure worked deeply into the soil before planting helps retain moisture and add nutrients. Soil should be slightly acidic (pH 5.5 to 6.5) Celeriac thrives in containers; a five-gallon pot will hold several plants.
Sowing: Sow in August to October, (8 to 10 weeks before last spring frosts). Celeriac are slow to germinate (2 to 3 weeks) and slow to get growing. Germination temp: optimum 20°C (68°F), min 18°C (64°F). Soaking seeds in water may aid germination.
Celeriac requires a soil temperature of at least 15°C (59°F). If you live in a warm climate then the seed can be sown directly into the soil in early September. Sow thinly at a depth of about 0.5cm (1/4 in). As the seedlings emerge, gradually thin the seedlings to about 30cm (1ft) apart in rows which are 35cm (14in) apart.
In cooler areas, sow indoors or in a greenhouse / cold frame. Sow two seeds to a small pot (7.5cm / 3in) in early September. Use fresh multi purpose compost and cover with a layer of fine vermiculite. Protect against slugs, as they can eat the tips off young plants. When the seedlings emerge, thin out the weakest growing one. The plants can be transplanted to their final positions from mid-November when the danger of frost is minimal. Acclimatise the plants to outdoor conditions for a week or two before planting outside.
Plant out so that the crown of the seedlings are slightly proud of the soil. This makes the seedling very susceptible to drying out in its first week or so, so gently and frequently water them. Try and settle the roots without washing soil over the crown. As you transplant give each plant a dose of liquid fish emulsion. When the plants are 7 to 10cm (3 to 4in) tall, mulch with straw to conserve soil moisture as we head into summer.
Cultivation: When they are first planted outside, water frequently if the conditions are dry. You can never give Celeriac too much water! Once established, watering should not be as necessary unless there is a drought. If the initial soil conditions were correct the roots develop well enough otherwise fertilise monthly with a low nitrogen fertiliser. Keep the plants weed free, frequent hoeing is the best solution. In January and February you may notice side shoots starting to grow from the side of the exposed root. Pinch these out as they emerge, they do not contribute to increasing the size of the root. By early March the roots will be swollen and visible above the ground. Unlike stalk celery, celeriac does not require blanching, but if you prefer white roots, scoop up some soil surrounding the roots and cover the parts which are above ground. This will keep the roots whiter because they will not be exposed to sunlight.
Harvesting: 95 days. March to August. Harvest small to medium sized celeriac roots for best flavour and texture. Begin as soon as the root ball reaches about 5cm (2in). They will grow to about 10cm (4in) in diameter. Celeriac can be stored after harvest but the best roots are from plants which have been freshly dug up. If your soil is free draining leave them in the ground and harvest as required.
A hard frost will damage them but they will withstand a light frost, it will only improve the flavour by spurring the conversion of its stored starches to sugar. To protect them from frost a layer of straw or hay laid around the base of the plants will provide some insulation. If a hard frost does threaten then lift the plants. Cut off the top foliage and store in boxes of slightly damp peat in a cool greenhouse or shed. The ideal storage temperature for celeriac is between 2º and 5ºC, with high humidity, so a refrigerator crisper also works well for long-term storage. Under these conditions, this vegetable will remain in good condition until late spring.
Lettuce, spinach and peas. Avoid proximity to squash, cucumbers, and pumpkins.