WHEN TO PLANT Start seeds indoors in February or March 10-12 weeks before the last frost. Sow seeds indoors or directly into the garden in May or June for a fall crop. In mild winter areas, celery can be sown in mid to late summer and grown as a winter crop. WHERE TO PLANT For spring planting, plant celery in full sun. When planting for the fall crop during the summer, protect your young seedlings by providing afternoon shade in hot, humid weather. Planting in the afternoon shadows of a taller crop like corn or pole beans will accomplish this. PREPARING THE SOIL Celery is a "heavy feeder" and requires continual attention to nutrient levels. Celery requires well drained soil that is rich with compost and well-rotted manure, and a pH level of 6.0-6.8. SEEDS AND GERMINATION Planting from seed gives you far greater variety than buying starts. Soak celery seeds over night to encourage germination. Celery seeds are usually good for up to 5 years after you've purchased them initially. The best soil temperature for germination is around 60F-70F, and it takes about 7 to 12 days to germinate in ideal temperatures; germination in cooler temperatures can take up to three weeks. Light does not seem to affect germination unless the temperatures at planting are above 70F. When temperatures are higher, the light helps to stimulate germination. GETTING STARTED INDOORS (for transplanting) Plant seeds in flats 1” apart using a mix of 2/3 part manure and 1/3 part sand. Cover seeds with 1/8” sand then cover top with wet burlap or damp sphagnum moss until the seeds sprout. Set flats out of direct sunlight in a location with good air circulation. Keep temperatures between 60-70F. Once the seedlings are 4” tall, transplant to peat pots.
PLANTING/GROWING (Planting seeds directly into the garden) Growing celery is not difficult given the right conditions. Celery is an ancestor to a marsh dwelling plant and requires plenty of water and protection from the hot sun. Harden off (put plant trays outdoors during the daylight hours) transplants for 10 days when the plants are 6” tall (before the taproot forms) and when it is two weeks past your last frost date. When hardening off, do not expose the transplants to temperatures lower than 50F or the celery may bolt to seed. Space plants 6-8” apart; space the rows 24" to 30" apart. Put a handful of compost in the planting hole before setting the plant in. Set the plants in the dirt no deeper than they are in the pots; the soil level should be the same. Feed the plants every couple weeks with a manure tea or fish emulsion. To maximize size and flavor, use a liquid organic leaf spray at the same time (every two weeks). Apply several inches of mulch to the base of your plants and provide at least 1” of water a week. Weeds will rob celery of nutrients so carefully pull any competing weeds, being careful of celery’s shallow root system. Apply compost tea and/or fish emulsion once a month though the season, and the liquid organic leaf spray every two weeks. If night temperatures are consistently below 55F, cover plants with hot caps to prevent plants from developing weak stalks. WATERING Celery needs more water than most vegetables in your garden; it requires a steady, generous supply in well-draining soil. Keep soil evenly moist throughout germination. COMPANION PLANTING & ROTATION Growing celery next to most garden plants is OK, but it is advisable to not plant side-byside with carrots or lettuce; these plants are susceptible to many of the same diseases. WHEN TO HARVEST Harvest celery before temperatures reach 75F. This will prevent bolting and bitterness. Harvest single stalks from the outside of the plants when needed. When harvesting the entire plant, cut at the soil line. Water plants the day before harvest for the best flavor and for longer storage capabilities.
For fall plantings, use row covers to protect from light frost. Harvest plants before a heavy frost hits. STORAGE Celery will keep in the refrigerator for a couple weeks. Harvesting the entire celery plant, roots with soil intact, and placing in a bucket with sand, will preserve your plants for several months with occasional watering when kept in a cool space (basement, cellar, or crawl space). Celery can also be dehydrated. COMMON PESTS AND PROBLEMS Boron deficiency: Browning of leaves and splits across stalk. Magnesium deficiency: yellow leaves Phosphorus deficiency: rosette will form on celery Solutions: Prepare your soil as noted in the "Preparing the Soil" section; attend to nutrients in soil through the season. Rotating your celery crop is your best defense against disease. A disease known as Aster yellows (transmitted from leafhoppers) can cause severe damage to your celery plants. Avoid planting near pastures or river and stream banks where the bacteria can be present in naturally occurring vegetation. Some symptoms of the disease are yellowing (not due to under-watering), an appearance of curly stalks, distorted leaves (giving them a melted appearance), or tall shoots stemming from just the center of the plant. Any infected plants should be immediately be removed and disposed of to prevent further spread of the disease. If leafhoppers are present, remove insects with a stiff stream of water from a spray nozzle, being careful not to damage the plants. Leafhoppers can usually be controlled with insecticidal soaps. If this is ineffective, use organics neem or pyrethrin spray as a last resort.