How to grow celeriac
Apium graveolens var. rapaceum · Apiaceae · Vegetable
Celeriac is a cool-season vegetable in the Apiaceae family, usually started indoors and set out as transplants. It wants full sun, though it tolerates a little afternoon shade in hot regions and plenty of water, especially in hot weather. From sowing to first pick is about 100–120 days. It shrugs off a light frost but a hard freeze will damage it.
Grower’s note: Grown like celery but for the knobby swollen crown. Needs a long, cool, evenly moist season. Surface-sow the tiny seed under lights and be patient. Strip side roots and lower leaves through summer for a smoother bulb; it stands into hard frost.
Sowing
Sow barely covered — the seed needs light to germinate, into soil between 55–75°F — germination is quickest near 70°F. It is slow and often erratic to germinate (14–21 days). For an early crop, start seed indoors about 11 weeks before your last spring frost and grow it under bright light.
Spacing & layout
Give each plant about 8″ along the row with roughly 24″ between rows. On a square-foot grid that is 4 per square foot. Allow at least 12″ of loose, workable soil for the roots. It grows well in containers at least 12″ deep.
Fitting it to your season
As a cool-season crop, celeriac does its best growing in the mild weather of spring and fall and tends to bolt or turn bitter in summer heat.
Quick facts
When to plant celeriac
Companions
Leek, Onion, Cabbage, Bush Bean
Carrot, Parsnip
Common problems
Pests: carrot rust fly, celery leaftier, slugs.
Diseases & disorders: early blight, late blight, septoria leaf spot.
Same family (Apiaceae)
Rotate these so they don’t follow each other in the same bed year to year.
Figures are typical home-garden ranges from Cooperative Extension planting guides, cross-checked against multiple state sources. Your variety and conditions will vary.