Plant 8 by 8 inches apart. This close spacing helps to blanch the stalks and smother weeds. Once the crop is established, mulch heavily with straw, grass clipping or other organic materials. Like cauliflower, celery likes moist soil. Do not let the soil dry out.
Moisture stress is the main cause of stringy, tough stalks.
Celery also requires large amounts of fertilizer. Apply a complete fertilizer with the compost and then after transplanting, apply one-half tablespoon of nitrogen fertilizer per four plants every two weeks throughout the summer. Too little fertilizer will not allow the stalks to grow tall and succulent. Harvest whole plants when they begin to size by cutting them below the soil. Some gardeners blanch celery with paper wraps, soil mounding around the plants or by growing them in a drain tile.