Celery is a heavy feeder and needs rich, moist soil. Add compost to soil and apply ¼-½ cup of complete organic fertilizer per 1.5m (5′) of row. Transplant when seedlings are 10-12cm (4-5″) tall. Avoid transplanting until night time temperatures are reliably at 10°C (50°F) or warmer. Space transplants 30cm (12″) apart in rows at least 45cm (18″) apart. Water frequently. Premature bolting may result from young plants being exposed to temperatures below 13°C (55°F) for several days.