Plant celery seeds in a temperature-controlled area of 70 to 75 degrees Fahrenheit 70 days before the planting date in September. Mix a well-draining soil of 2/3 compost and 1/3 sand, and fill growing flats within 1/4 inch of the top.
Soak seeds in water overnight, and scatter them on the soil surface. Cover them with 1/8 inch of sand and water thoroughly. Cover the flat with moist burlap until the seeds germinate.
Uncover the flat, and place it in bright indirect light. Keep the young plants uniformly moist.
Pick seedlings out of the flat when they are 4 inches tall. Put them in peat pots. When they are 6 inches tall, harden them off to be transplanted into the garden, which should be in September. Move them gradually into brighter light and outdoor conditions over a 10-day period.
Plant celery seedlings, peat pot and all, into soil that is well drained but has a good water-holding capacity. Water them immediately, and keep them uniformly moist as shallow roots dry out quickly.
Fertilize celery every two weeks with a balanced fertilizer, such as 5-10-10 NPK ratio, or with manure tea.
Keep weeds from becoming established. Remove them while young so the celery's root system is not disturbed by large weeds being pulled out.
Blanch celery plants if desired for milder flavor. Cut tops and bottoms from half-gallon clean milk containers to make a sleeve. Put this over individual celery plants to cover the stalk areas for two weeks before harvest.
Harvest celery from November to January. Dig individual plants carefully with a narrow spade so root systems of neighboring celery won't be harmed.