Celeriac

Commonly called celery root, celeriac is an odd-shaped root vegetable related to celery, carrots, parsley, and parsnips. With a starchy flesh similar to potatoes, its subtle, celery-like flavor has nutty overtones, often described as a cross between celery leaves and parsley. Eaten roasted, baked, or raw, celeriac must be peeled to remove a tough skin that may amount to nearly a quarter of the root.

Old and New Varieties

Choose among old European favorites of this ancient vegetable or opt for newer varieties. The European strain 'Brilliant' has nearly fiberless, white roots. ‘Alabaster’ and ‘Marble Ball’ have strong celery flavor, light-colored, smooth skin, and store well. ‘Large Smooth Prague’ (also called ‘Giant Prague’) produces knobby, crisp, white roots that store well.
'Diamant' has a white interior, stands above the ground for easy harvesting, and stores well. ‘Yara’ is slow to bolt; ‘Monarch’ has easy-to-peel skin and a long storage tolerance.

Sowing and Growing

Evaluate your microclimate before planning to grow celeriac. Success depends on exposure to mild temperatures like those near the coast with a range from 50-75 degrees while it grows.
Locate planting beds in full sun or very light shade fortified with plenty of rotted manure or compost to create fertile, humus-rich, moisture-retentive soil.
Sow seed indoors as early as 10 weeks before the average last frost date in spring. Plants can go into the garden 10-12 in. apart on the average date of last frost or after air temperature reaches 65-75 degrees and soil is warmed to 60-65 degrees. Alternatively, sow seed directly after soil warms. Cover with a light sprinkling of soil and keep moist—light is required for germination which may take 2 weeks or longer. Rarely will all seeds sprout.
Avoid planting in cool soil or plants will run to seed without forming a large root.
Sow a late summer crop in microclimates where there is enough time for a second harvest. Plan on 100-150 days to maturity. Celeriac will increase with flavor following a light frost.
Keep the top few inches of soil moist (not wet) at all times. Celeriac is shallow rooted and requires even, regular watering.
Avoid weed competition for water and nutrients; cultivate carefully to avoid shallow roots.
Snip off side roots as the large root develops and hill up soil over the swollen bulbous root to blanch it. The outside of the root will blanch white but the flesh of some varieties will remain a brownish color. Roots that push above soil level with no hilling may become larger.
Use a garden fork to lift the bulbous roots when they reach 3-4 inches across or slightly larger.
Cut stems close to the knobby root.
Expect tall stems and pithy roots if biennial celeriac remains in the ground for a 2^nd year.

Pests and Diseases

Practice crop rotation of related vegetables (celery, carrots, parsley, and parsnips) every 1-2 years to avoid soil pests and diseases.
Pick off and destroy any yellow leaves or those showing small holes and tunnels from celery leaf miners. These small insects do minimal damage as long as you keep their numbers in check.
Handpick snails or slugs or apply an organic material targeting them following label directions.

Additional Information

Sonoma County Master Gardener Vegetable Planting Summary.
https://sonomamg.ucanr.edu/Food_Gardening_with_Less_Water/
https://vric.ucdavis.edu/pdf/celery.pdf

February 2022