Vegetable · Apiaceae
Celeriac
Apium graveolens var. rapaceum
Hand it a long season, rich soil, and water that never quits, and celeriac pays you back with a knob no store can match.
Full sun
Every 2–4 days
50–77°F · 10–25°C
100–120 days
Overview
Celeriac is celery raised for its root rather than its stalks. It sits in the carrot family and shares a species with regular celery, yet breeders have funneled the plant's whole drive into a swollen, knobby base instead of crisp stems. Crack the rough skin and you find dense, ivory flesh that tastes like celery with a nutty, earthy twist.
Here is a crop for the patient gardener. It moves slow out of a finicky seed and wants a long stretch of 100 to 120 days, paired with steady moisture from start to finish, before the knob fills out. Push it along or let it dry and you harvest small, fibrous roots, which is exactly how celeriac earns its demanding name.
Your reward is a vegetable that keeps for months and pours deep flavor into soups, mashes, and roasts. Nail the basics and a single plant hands you a knob the size of a fist or bigger, ready to store well past the first frosts.
Care
The short version: full sun and rich, deep soil, water that holds the ground evenly moist all season, a monthly balanced feed, and the patience to grant it a full 100-plus-day run.
Light
Celeriac craves full sun to bulk up a worthy knob, though it will accept a touch of afternoon shade where summers turn fierce. Shortchange the light and the plant just creeps along over an already lengthy season.
Water
Here is the make-or-break factor. Celeriac is a heavy drinker that demands evenly moist soil for the whole season, frequently a deep watering every 2 to 4 days. Let it parch even for a moment and the knobs arrive small, hollow, or cracked.
Soil
Settle it into rich, deep loam loaded with organic matter that grips water without going soggy. A pH between 6.0 and 7.0 keeps it happy, and working in plenty of compost stations both the moisture and the feeding it hungers for right at the roots.
Temperature
Celeriac thrives in the mild band of 50°F to 77°F (10°C to 25°C). A cold snap below about 50°F (10°C) on young plants can spark bolting, so warmth at transplant time counts every bit as much as warmth through summer.
Humidity
Plain garden humidity, roughly 40% to 70%, is the whole of its request. What matters far more is keeping the foliage from staying wet, since packed, damp leaves welcome the blights that dog this crop.
Feeding
Celeriac is a heavy feeder after a balanced fertilizer with steady nitrogen, served about monthly straight through the growing season. Rich soil teamed with regular feeding is what powers the plant through its long haul to a full-sized knob.
Pruning
Not much falls to you here. Snap off any lateral side shoots, and late in the season peel away the lowest, oldest outer leaves to bare the crown of the knob. Never cut the central foliage, because that is the engine driving the swelling root.
Repotting
Not applicable; grown in the ground or large beds, not as a container houseplant
Size & spacing
Plants climb to 1.5 to 3 feet (46 to 91 cm) tall and 12 to 18 inches (30 to 46 cm) wide. Tuck them in tight, about 6 inches apart down the row, a spacing trials have proven actually yields the largest marketable roots.
When to plant
Celeriac claims the entire growing season, which puts the calendar front and center. Sow seed indoors in late winter, move sturdy transplants out only once the last frost has cleared and the soil has warmed, then lift the knobs from late summer into fall before a hard freeze rolls in.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 8-10 weeks before the last spring frost; seed is slow to germinate, surface-sow and keep warm and moist
- Plant: Transplant after the last frost once soil has warmed and seedlings are sturdy (late spring)
- Harvest: Harvest from late summer into fall once knobs reach 3-4 inches across, before a hard freeze
Hardiness
USDA hardiness zones: 4–9
Temperature: down to -34°C
Troubleshooting
Nearly every celeriac problem turns up in the size of the knob or the condition of the leaves, and the root cause tends to be water, cold, or crowding. Scan the early signs below and pair them with what your plants are showing. Spotting trouble fast is what separates a fist-sized root from a fibrous flop.
A seed stalk rockets up while the knob goes woody
What you are seeing is bolting, set off when a cold spell fools the biennial into believing winter has already come and gone. Once that seed stalk climbs, the root stays small and stringy with no road back, so yank it and begin again. The fix is timing: hold transplants in warmth and resist setting them into chilly ground too soon.
Fix:
- Pull and discard bolted plants; the root will not improve
Knobs turn out undersized, split, or hollow within
Nine times out of ten the culprit is thirst, because celeriac guzzles water across its long run and one dry stretch halts the swelling permanently. Too little boron can hollow and brown the middle too, and tight spacing or a season cut short leaves roots stunted. Soak deeply on a steady rhythm, feed generously, and hand each plant about 6 inches of elbow room.
Fix:
- Maintain even deep watering
- Ensure adequate fertility and balanced micronutrients
- Allow the full long season and proper spacing for bulking
Brown and gray blotches creep across the leaves
This is a fungal leaf blight, typically Cercospora or Septoria, which moves in wherever the leaves sit wet and packed together. Pluck the spotted leaves, thin the planting so air flows through, and aim your water at the soil rather than the canopy. Shifting the bed to fresh ground each year stops the spores from overwintering and coming back.
Fix:
- Remove affected foliage
- Improve spacing and air flow
- Water at the base rather than overhead
Leaves go chewed, curled, or tacky underfoot
That sticky sheen flags aphids and the honeydew trailing behind them, while torn, ragged holes usually signal celery worm, slugs, or earwigs grazing the tops. Good news: none of it reaches the root you came for, so pick off the caterpillars and slugs by hand and blast the aphids with a spray of water. A strong, well-watered plant brushes off most of the damage.
Fix:
- Hand-pick caterpillars and slugs
- Hose off or treat aphids as needed
Toxicity
Celeriac is a food crop that holds nothing toxic to pets, livestock, or people. The root is safe for all comers, and the lone mild catch lives in the leafy tops: their natural furanocoumarins can leave touchy skin sore after handling them under bright sun. Pull on gloves for that single chore and you have nothing to fret about.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Nothing toxic to flag. A cat that chews a leaf may feel a quick bit of tummy upset from the strange greens, and that is the extent of it.
Dogs None
Dogs are clear, leaf and root both. Plainly cooked celeriac turns up in plenty of homemade dog dinners.
Horses Safe
Let horses graze or eat celeriac freely; the plant holds nothing that would harm them.
Rabbits Safe
Leafy tops and root alike suit rabbits in moderate helpings, served as one piece of a varied diet.
Livestock Safe
Cattle, goats, and sheep take celeriac in stride; it grows as feed, never a danger to the herd.
Birds Safe
Backyard chickens and other birds may peck at the tops and trimmings with no harm done.
People Safe
Cooked or raw, the root makes good eating. The single small snag lies in the foliage, which carries furanocoumarins that can leave touchy skin tender after working the tops under bright sun, so glove up and wash afterward.
Like other Apiaceae (celery, parsnip), the foliage contains furanocoumarins (psoralens) that can cause mild phytophotodermatitis in sensitive people who handle the tops in bright sun. This is milder than parsnip and is a minor handling note, not a pet-poisoning risk.
Varieties
Celeriac cultivars part ways mainly on size, smoothness, and how cleanly the flesh holds its white color within. A handful of names keep cropping up in gardens and trials alike.
Balena
A strong, generous yielder that pushed out the largest marketable roots in University of Maine trials, all the more so at a tight 6-inch spacing.
Brilliant
A dependable mid-season grower bearing smooth, rounded roots that hold off the internal browning celeriac tends toward.
Diamant
Smooth-skinned roots showing scant browning inside, and they hold up nicely in storage.
Giant Prague
The time-tested heirloom, valued for big, globe-shaped roots that carry comparatively few of the side rootlets that turn peeling into a chore.
How to propagate
Celeriac travels just one road, from seed, and that seed is the trickiest stretch of the whole crop to nurse along.
SeedModerate
Start indoors 8-10 weeks before the last spring frost · Roughly 2-3 weeks to germinate and about 10 weeks to reach transplant size before setting out
Seed is the only route into celeriac, and it puts your patience to work right away. Those specks are tiny and sluggish, needing 2 to 3 weeks to break the surface, so press them onto the top of the mix with light, hold them warm and evenly moist, and get going a solid 8 to 10 weeks ahead of your last frost. Plan on about 10 weeks before they hit transplant size, then harden the seedlings off ahead of planting out.
Myths
Celeriac is a completely different plant from celery.
Both are one species, Apium graveolens, simply bred toward different parts. Celeriac is the root-grown variety rapaceum, and the everyday stalk celery is variety dulce, which makes the pair near relatives rather than strangers.
The knobby edible part is a true root.
That bulging knob is largely an enlarged hypocotyl and stem base, not one taproot at all. The genuine fibrous roots are those stringy threads dangling off its underside.