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!
Celeriac ‘Apium graveolens var. rapaceum’ Plant Overview
| | |
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?
This slow-growing crop is planted in spring or early summer and harvested in the fall.
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?
France first documented celeriac as a food plant in the 1600s.
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
To ensure successful growth, it’s advisable to start these plants indoors.
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
Establish a sheltered patio area for hardening off when the weather is stable.
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 Transplant
When transplanting, treat the plants delicately to avoid harming the root balls.
Celeriac transplants similarly to any other vegetable. Handle the plants gently and avoid squeezing or cramming the root balls. If you use specialized planting trays with finger holes in the bottom (like the Epic 6-Cell Trays), it’s easier to push the seedling root ball out of its container without damaging the taproot.
Prepare holes about 1.5x the size of the seedling roots and ensure they are planted at the same soil depth (no deeper, no shallower) as they were in their containers.
Spacing
If you’re growing smaller roots, you can place them closer together.
Set celeriac plants 6-8” apart in rows 18-36” apart. Closer spacing is sufficient for smaller roots. Consistent, steady moisture is essential after transplanting and throughout the growing process. I like to spread soaker hoses or drip lines between each row and irrigate every time the upper few inches feel moderately dry.
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.
Light
These plants need at least six hours of direct sunlight daily.
Grow celery root in full sun in northern climates and partial shade in warmer zones. The plants appreciate six hours of direct light daily but tolerate even less sunshine if necessary. In regions with hot summer weather, dappled shade is important to keep the plants cool.
Water
To ensure healthy growth, maintain consistent soil moisture for your crop.
The soil should never dry out, but you should avoid sogginess or overwatering. Like celery, this crop is sensitive to water and demands a consistent supply of soil moisture. If you grow in extra loamy, rich soil with a light layer of leaf or straw mulch, your roots are more likely to be successful because they will be protected from drying out.
Stunted or weird-looking roots are common in plants without enough water or irregular watering (large fluctuations between moist and dry). When in doubt, stick your finger a few inches in the soil and check that it feels like a wrung-out sponge. Water 3 to 4 times per week during dry summer months. Avoid overwatering or soggy soil in the wet spring and fall, which can lead to root rot.
Soil
Ensure the soil has a pH of 6.0-7.0 and ample organic matter for water retention.
This knobby root crop prefers fertile, loamy soil. It thrives in beds with plenty of compost and drainage. Since celeriac doesn’t take up too much space but stays in the garden for a long time, I like to plant it in the corners or margins of my best raised beds where tomatoes and peppers grow in the center throughout summer.
Be sure the soil has a pH of around 6.0-7.0 and plenty of organic matter to aid in water retention. Vermicompost (worm castings) is especially beneficial for this crop!
Climate and Temperature
Celeriac thrives in mildly warm temperatures for most of its growth cycle.
Celeriac is technically a cool-season crop because it is planted in early spring and harvested in the fall. However, it enjoys mildly warm temperatures throughout most of its growth cycle. A steady 60-70°F (16-21°C) is ideal, but no climate will be perfect all the time.
I like to use row fabric to moderate the temperature and protect fragile young plants from nighttime dips. Once the bulbs are more mature near the end of the summer, plants can handle mild fall frosts, but it’s best to harvest them before hard frosts set in for optimal storage.
Fertilizing
Without sufficient nutrition, celeriac roots may remain small and stem-like.
These large, dense roots require a lot of fertility to fuel their growth. Celery root is considered a heavy feeder and benefits from a generous helping of all-purpose slow-release fertilizer.
If the plants don’t have enough nutrition, celeriac roots may not swell out and can stay looking like knobby stems. A hefty application of compost is also beneficial for supplying micronutrients and microbial activity.
Harvest and Storage
It is crucial to harvest before the first hard freeze to prevent frost damage.
You can technically harvest celeriac at any time once the bulbs are at least three to five inches in diameter. I start picking the largest roots in late summer and leave some to develop into the fall. The flavor improves after the first frost because the cold weather concentrates the sugars and aromatics. However, it is very important to pull the plants before the first hard freeze because frost damage can lead to mushy, sunken, or blackened areas of the roots.
The coolest thing about celeriac is its storage capability. It can last six to eight months under the right conditions, providing tasty sustenance alongside winter squash throughout the coldest months. The key is to cut the tops ¼ inch above the roots and trim off the mangled, hairy roots from the bottom. Try not to knick the outer skins! They may look ugly now, but they are important for storability.
Wash and store the roots in a refrigerator or cooler at around 33-38°F (1-3°C) with 95-98% humidity. A ventilated bag is ideal.
Varieties
Select the celeriac variety that matches your culinary preferences and kitchen requirements.
This Mediterranean root comes in several cultivars, including old-time heirlooms and modern hybrids. Look for a celeriac with your desired level of “celery flavor” and a desirable size for your kitchen use.
Popular choices include:
- ‘Giant Prague’: Large white roots, strong celery flavor, heirloom from 1870
- ‘Monarch’: Easy to peel, smoother skin, mild flavor, raw or cooked
- ‘Alabaster’: Strongly pronounced celery flavor, large roots, tender, pure white flesh
- ‘Brilliant’: Medium-large roots, white centers with aromatic nutty flavor, resists pithiness
- ‘Belenga’: Hybrid, vigorous, best bolt tolerance, resists pithiness
- ‘Prinz’: Smaller plants and bulbs, smoother white skin
- ‘Mars’: Extra large plants, medium celery flavor, firm interior, holds well in the garden
Companion Plants
Since celeriac stays in the garden for almost the entire season, companion planting is essential to maximize space and prevent pests.
However, avoid planting it near carrots or celery because these relatives can attract the carrot rust fly and spread mosaic viruses between each other. Good same-bed companions include:
Cabbage
You can grow this cold-loving crop alongside celeriac in both spring and fall.
This cool-weather cole crop can be grown around the same time as celeriac in spring or fall. Its low-growing stature won’t shade out the plants. It enjoys the same fertile soil and consistent moisture.
Lettuce
Lettuces are suitable plants to grow alongside celeriac and harvest when young.
You can use lettuce as a nice, light feeder to tuck in near celeriac plants and harvest young. You can grow head lettuce or salad greens in the same beds for several successions while celery roots develop.
Onions
Onions naturally deter pests from celeriac and don’t overcrowd the growing area.
Thanks to their pungent sulfurous smell, onions naturally repel pests from celeriac. They also have a similar bulbous growth habit that won’t compete too much for space. Ensure at least six to eight inches of space between onion plants and their neighbors.
Pests and Diseases
While this celery relative is usually pest-free, there are a few to look out for. Certain bugs may hop on the plants, but they aren’t always detrimental. Similarly, most of the main diseases that affect celeriac are fairly easy to prevent with proper soil, nutrition, irrigation, and seed selection.
Aphids
These tiny sap-sucking pests can harm your plants by reducing yields and stunting their growth.
Little green or white aphids may appear on celeriac plant leaves during the warmer months. These little sap-sucking pests may reduce yields and stunt the plants. They can also spread celery mosaic virus if it is present in your garden or neighboring areas.
The best way to remove aphids is with a firm blast of water and a preventative application of horticultural oil or diluted neem oil. Nearby plants like white alyssum, marigolds, or flowering dill can attract beneficial predatory insects to keep aphids in check.
Slugs
To eliminate slugs, start by clearing mulch and debris from the plant base.
In heavy clay soils or extra wet conditions, these slimy pests leave noticeable trails on your celery roots while subtly munching away at the developing skins. The best way to get rid of slugs is to first clear any mulch or debris away from the plant base.
Then, create a beer trap by pouring cheap beer into a shallow plastic container and nuzzling it into the soil near the plants so the slugs will fall into the trap. In dry weather, you can also try diatomaceous earth or an organic slug bait.
Carrot Rust Fly
Use row fabric to shield your plants from carrot rust flies.
Carrot rust flies are attracted to most of the Apiaceae (umbelliferous) crops, including carrots, parsnips, celery, and celeriac. The adult flies smell the plant and lay eggs at the crown base. Then, the larvae hatch and burrow down, leaving unsightly holes and tunnels in the roots. You may notice rust-colored frass (poop) near the tunnels on the root exteriors.
Research shows that these flies are most active in early summer, so it’s helpful to keep your plants covered with row fabric so they can’t smell the celeriac. Avoid planting carrot-family crops in large clusters.
Interplanting with onions, leeks, or chives is especially beneficial for distracting carrot flies from the scent of your crops. In the event of a major infestation, consider a neem or pyrethrum application according to package instructions.
Armyworm
Armyworms make irregular holes in celeriac foliage.
If you see holes in the foliage of your celeriac that have an irregular shape, you may be dealing with armyworms. Spotting these caterpillars on your plants is a surefire sign. You can hand pick these off the plants and feed them to birds or use BT sprays to eliminate them as they feed.
Root-Knot Nematode
Root-knot nematodes are tiny parasites that feed on plant roots.
Have you noticed galls on the roots of your plants as you harvest them? This is a sign of root-knot nematode infestation. These tiny parasites feed on the roots of plants, distorting them as they go. Proper crop rotation generally prevents this microscopic pest.
If you find they’ve been feeding on your crops, avoid planting in the area, and treat them with beneficial nematodes with two treatments two weeks apart. Wait for temperate weather to do this.
Celery Leaf Spot
To prevent the spread of celery leaf spot, use disease-free seeds and avoid overhead watering.
Also known as early blight, this fungal infection looks like large dark brown spots irregularly shaped around the veins of celeriac and celery plant leaves. It is important to source quality disease-free seed and avoid overhead watering to help prevent its spread.
If celery leaf spot appears, you can remove infected leaves or apply an organic copper fungicide to stop its spread. Crop rotation of all Apiaceae-family crops (carrots, parsnips, celery, parsley, etc.) is essential.
Black Heart
Ensure you incorporate high-quality calcium like oyster shells or dolomite lime during planting.
Blackheart is not technically a disease but a physiological disorder of celeriac and celery. Calcium deficiency can cause plants to develop a rotten or hollow interior, rendering them inedible. The key is to amend with quality calcium at the time of planting, such as oyster shell or dolomite lime.
Celery Mosaic Virus
Although the disease doesn’t spread through seeds, resistant cultivars are an option.
Mottled leaves, dwarfed plants, and twisted contorted stems are common symptoms of this viral disease that is spread by aphids.
The primary means of control is to prevent and kill aphid populations, which act as the primary vector. The disease is not seed-borne, but there are resistant cultivars available.
Damping-Off
Avoid overwatering seedlings to prevent damping-off disease.
Pythium spp. and Rhizoctonia solani cause this disease that strikes celeriac seedlings. In the case of damping-off, seedlings to grow to a certain point and then rapidly die. Seeds may rot before they germinate, and those seedlings that die display reddish lesions at their base.
The only way to deal with damping off is to plant seedlings in well-draining starting mixes and water only as much as they need. Too much water and poor drainage are the main ways to foster the pathogens that cause the disease.
Downy Mildew
Gray fungal growth on leaf undersides may indicate downy mildew.
Another common disease is downy mildew. The leaves may take on yellow splotches with gray fungal growth on their undersides. If there are just a few leaves displaying symptoms, remove them. Prevent the disease by watering deeply at the base of the plant and planting only disease-resistant varieties.
Plant Uses
The leaves and stalks are generally not suitable for consumption.
Celeriac is used for its starchy roots, which need to have their skin removed before cooking. The leaves and stalks are not typically considered edible.
FAQs
Celeriac is not a difficult crop to grow, but it requires a lot of patience and attentiveness during the early stages. The plants take 2-3 weeks to germinate and up to 120 days to mature. They cannot be exposed to cold temperatures under 55°F (13°C) within the first few months, otherwise, the young plants will bolt. Once the weather is consistently settled, they can be transplanted into the garden, where they need consistently moist soil for the remainder of their life. Regular watering and high fertility are key for successful harvests.
Celeriac thrives in loamy, rich, fertile soils in full sun or partial shade. It does best in mild climates where temperatures are not too hot nor too cold. While the plants are vulnerable to bolting when exposed to cold weather during early growth, they are tolerant of light frosts in fall once the roots begin to mature.
Celeriac is a small-space crop that only needs 6-8” between each plant. It can be grown in a 5-gallon pot or grow bag as long as the soil is rich, loamy, and consistently moist. The roots don’t grow super deep, but benefit from at least 12” of soil in their container.
Final Thoughts
Celery root may seem like a lot of trouble for such an ugly veggie, but it is incredibly rewarding and even slightly addicting once you get the hang of it.
Remember to:
- Start early! Sow seeds indoors 10-12 weeks before your last frost.
- Avoid exposing young plants to temperatures under 55°F (13°C).
- Wait until the weather has settled in early summer to transplant.
- Use row cover to moderate temperatures and deter carrot rust flies.
- Maintain consistent moisture so the soil is never too dry, nor too soggy.
- Amend with lots of compost and calcium-rich oyster shells.
Once you taste mashed celeriac, roasted celery root, or celeriac-leek soup, you won’t want to go through another winter without it!
