Start seeds indoors 8-12 weeks before your last spring frost (February-April). Sow at least 2-3 seeds per tray insert cell. Celeriac seed germination is known to be irregular. Planting multiple seeds in one container will allow you to thin them down to 1 plant each. Seeds should be planted no more than 0.25 inches deep as celeriac seeds need light to germinate. You may sow then on the surface and lightly sprinkle a thin covering of soil to help maintain moisture contact. Celeriac likes a moist environment; do not allow the soil to dry out. Preferably maintain germination temperatures of 70-75F. Expect 14-21 days to germinate. Plant in nutrient-rich, moist soil with a ph of 6-7.5.

Transplant in the spring once the last potential frost date has passed, usually around May-June. Make sure air temperatures are reliably 65-75F or soil temperatures are 60-65F. Celeriac grows best when temperatures are stable from 50-75F. Early cool temperatures may cause bolting (early flowering). This should be avoided as bolting slows root development as a focus is put on flowering and seed development.

Celeriac is harvested for its swollen root (stem base) when it is about 4 inches in diameter. However, the whole plant is edible. To remove your mature plant, gently loosen the soil around the base. Lift the plant out of the soil. If planted in the spring, your celeriac should be mature and ready for harvest as soon as October but may be left in the ground until you are ready to use it as late as the next spring. Keep in mind the root may become pithy if left to the second year of growth. The flavor also intensifies with time. Many people recommend harvesting after a frost for the best flavor profile. If you decide to leave it in the ground to overwinter, cover with straw to keep the roots and soil from freezing. Stems should be cut close to the knobby root.