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Have you ever heard of a vegetable that looks like an asteroid but tastes like earthy chicken soup? Celeriac is a lesser-known root vegetable with a subtle nutty flavor accented by hints of celery and earthy turnip.

Though it looks like the ugly duckling of the vegetable world, it has a deliciously dense, starchy texture like a potato. When you roast, mash, or blend it into soups, it adds that nostalgic “chicken soup” vibe and smooth creaminess to eat while you cozy up next to the fire.

Also known as celery root, this unique crop is closely related to celery and requires similarly mild climatic conditions through spring and summer. After its early fall harvest, the roots store excellently through winter and complement your favorite winter squash, beets, potatoes, cauliflower, and leeks.

Celeriac takes up to 120 days to mature, but it is lowkey in the garden and rewards patience with giant knobby roots. The key is to start early and transplant after the risk of frost has passed. Otherwise, these technically biennial plants will bolt prematurely. Let’s dig into everything you need to know about growing celery root!
History and Cultivation
Celeriac has historically been used throughout Europe and North Africa, but its strange appearance has taken time to catch on in the States. With its knobby skin and hairy, tangled roots, it is certainly not the prettiest vegetable alongside gorgeous tomatoes or colorful winter squash.

However, celeriac is a joy to cultivate and even more fun to eat. Once you cut away the deceptively ugly skin and roast or boil it, the delicious bulbous root reveals a strikingly unique flavor with notes of turnips, mushrooms, nuttiness, and, of course, a faint celery tone.

What is Celeriac?
The vegetable called celeriac is a knobby root vegetable sometimes referred to as celery root, knob celery, or turnip celery. It has the texture of a potato and an earthy flavor, perfect for soups. It is a slow-growing crop planted in the spring or early summer and harvested in the fall for autumnal roasts and winter root storage.

Celery root is closely related to celery and parsley, noticeable by its flat, toothed leaves and green fleshy ribbed stalks. However, the stalks of celeriac are not to be eaten. The large, spherical, bulbous root often emerges above the soil and averages 4-6” in diameter. The gnarled, unsightly skins are easy to cut or peel away to reveal the delicious white fleshy interior.

Where Does Celeriac Originate?
Like its close cousin, celery, celeriac likely originated in the Mediterranean. Though it is often called celery root, the plant is its own variety. Celeriac is a descendant of wild celery (Apium graveolens), first cultivated in ancient Egypt as a medicinal plant. The leaves of wild celery have been found in Egyptian pharaoh tombs.

It was first recorded as a food plant in France in the early 1600s and promptly spread throughout North Africa and Europe as a staple winter root. While celeriac has been available in the United States since the 19th century, it has only recently become popular in the foodie scene.

Propagation
Requiring up to 120 days to mature, celeriac is not a crop for the impatient gardener. This winter root is propagated by seed beginning in the early spring. While the plants are moderately cold-tolerant at maturity, they are very cold-sensitive as babies.

The biggest mistake you can make with celery root is transplanting it too soon. Seedlings exposed to temperatures under 55°F (13°C) for ten days or more in the early growing stages are highly prone to bolting (going to seed).

Celeriac is technically a biennial (two-year) crop that we grow in our gardens as an annual. This means we have to take extra care to seed and transplant at the proper time with the right conditions.

Seed
Celery root can be difficult to find as a nursery start, but the seed is widely available. Starting indoors is recommended in most climates due to the young plant’s sensitivity to cold temperatures. Seeds should be sown in cell trays in early spring, 10-12 weeks before your last frost date. In southern zones 9 and warmer, celeriac can be grown from fall seeding through the winter.

Prepare cell trays with a well-drained seed starting mix. Sow two seeds per cell at a depth of about 1⁄8 inch and very lightly cover with soil mix or vermiculite. Light is needed for germination, so you don’t want to bury them too deep. The soil needs to remain consistently moist and around 70-75°F (21-24°C). Germination heating mats are useful until the seeds emerge 2-3 weeks after sowing. At that point, the temperature can be reduced to 60-70°F (16-21°C).

Since this crop is started in such early spring when barely anything else is growing, it can take up prime real estate, such as a warm south-facing window, a small greenhouse, or your indoor grow light setup.

When seedlings develop two sets of true leaves, thin to 1 plant per cell and up-pot to larger cells if desired. Continue growing indoors until the weather thoroughly settles, several weeks after the last frost date. Celeriac is often hardened and transplanted around late May to mid-June in most temperate regions.

Hardening Off
Acclimating your seedlings is extra important with this temperature-sensitive crop. If you can get the celeriac past the seedling stage, it will be smooth sailing for the rest of the season! Be sure to harden off the seedlings for about one week before transplanting by slowly reducing water and carefully exposing them to outdoor conditions.

It is vital to keep baby celeriac plants above 55°F (13°C) ambient temperature. If exposed to temperatures colder than 55°F for more than 7-10 days, they will likely bolt (go to seed), and your crop will be lost.

This happens because celeriac is a biennial plant, which means it usually works on root and leaf development in its first year of growth and then focuses on seed production in the second year. The cold weather confuses the young plants to think they have already passed through the first year of growth, causing them to prematurely go to seed before they develop bulbs.

To prevent this, harden off the celeriac in a protected patio area when the weather has settled. The best trick I’ve found is to keep young plants covered with row fabric for the first several weeks outdoors throughout the hardening and transplanting stages. Row fabric keeps them warm and cozy while physically excluding pests that may want to prey on vulnerable young plants.

Planting
Wait to transplant the celeriac until the plants are thoroughly rooted with several sets of true leaves and the weather outside is consistently above 55°F (13°C). If you have properly hardened off the seedlings and patiently waited for warm weather, the rest of the growing process should be fairly easy.
How to Grow
This long-season crop is fairly straightforward to grow. Like its celery cousin, celeriac is sensitive to moisture and has virtually zero drought tolerance. A continuous moisture supply is necessary if you want nice roots with an appealing crisp texture and no hollow or pithy centers.