The wild celery plant - from which cultivated varieties are selected - is found on boggy riversides and marshy ground, giving a clue to the growing conditions it needs. Soil should be moisture-retentive and never dry out. Celery hearts are particularly tasty and can be eaten raw or braised by simmering. To plant celery seeds, follow these steps: Sow the seeds indoors 14 to 6 weeks before the last spring frost. Sow the seeds ⅛ inch deep (3 mm). Soak the seeds overnight in water before sowing. Blanching celery varieties should be planted in a trench 12 inches (30 cm) deep by 18 inches (45 cm) wide. Celery seeds will take about 2-3 weeks to germinate. Learn how to grow celery from seed indoors or outdoors for different harvest times. Celery seed takes about 21 days to germinate. Light helps celery seed germinate; do not plant the seed deeper than ¼ inch. Warm days and cooler nights, also help celery seeds germinate. Keep the soil evenly moist during the germination period.