Celeriac takes longer than most vegetables to reach maturity and requires a soil temperature of at least 15°C for proper germination. Sow indoors, two seeds in 7.5cm (3”) pots about 1/2cm (1/4”) deep in early March. When the seedlings emerge, thin out the weakest one. Plants can be transplanted in mid-May when the danger of frost is minimal. Approx 30cm (12”) between plants in rows 35cm (14”) apart. Be sure to harden plants off prior to placing them out.