How To Start Celery From Seed

5 from 2 votes

How to grow celery from seed and nurture it throughout the growing season until harvest, storing and seed saving.

Seed starting trays - Waterproof seedling trays
Starter pots - 48-cell inserts or 3" pots or all-in-one seed starting kit
Soil blockers (pot-less system) - Ladbrooke original micro 20 soil blocker and Ladbrooke mini 4 blocker
Seed Starting Mix - seed starting mix
Grow lights (shop lights) - 4-ft LED shop lights
Small clamp on grow light - Table mount grow lights
Fish Emulsion or Compost tea - fish emulsion and optional: EM-1
Compost - Make your own or get a few bags of compost
Transplanting and cultivating tools - cobra head cultivator, dibber and the hori hori knife

Celery has a bit of a slow germination habit and that could be frustrating. It can take up to 3 weeks before you see the little green baby leaves appear, so be aware and try to be patient with this girl. Keep the temps above 55 degrees to prevent premature bolting throughout the growing stages. When hardening her off, be sure to keep the temperatures up, but reduce watering.

Prepare your growing flat or pots. Fill with a quality seed starting mix that has been pre-moistened. To pre-moisten the soil, I like pour it into a cheap dishpan (from Walmart or Dollar Store) or, for larger amounts, a concrete mixing pan. Add water and mix thoroughly. Get it damp but not wet. When you squeeze it it should just release a few drops of water.
Tap your pots or flat onto the table a few times to get the soil mix to settle.
Sprinkle a few seeds over the surface. Don't cover, or very lightly sprinkle a bit of soil mix or vermiculite over it. Like barely! I don't cover mine at all, I just press the seeds into the surface a bit so they have good contact with the soil and then I put a sheet of plastic wrap or one of those greenhouse covers over the tray, to keep the soil moist.
Now you play the waiting game and while you wait, check every now and then to make sure the surface stays moist.
Technically you don't need lights if you keep the trays near a window, until germination. Once they germinate though, you'll need to place them under lights immediately. Keep the lights no more than 2" above the seedlings. Raise the lights as the seedlings grow. They will need 14-16 hours of light per day.
Once the seedlings have reached a 2" height, you can carefully transplant them into individual pots in case they are crowded. Or, if you used small cells to plant your seeds into, thin to one plant per cell or pot. They are ready for transplanting when they are 3" tall.

Harden plants for a week before transplanting by exposing them to the elements and full sun gradually. Start with an hour, and increase each day. Reduce watering for the week, but don't let them dry out.
Transplant once night temperatures are above 40 and soil temperatures are above 55 degrees, to prevent bolting. I like to give the plants a soak in some fish fertilizer solution, EM-1, or compost tea just before transplanting, so they can soak up some nutrients to minimize transplant shock.
Plant the celery into compost-enriched soil. 8" apart for leaves and 12" apart for celeriac roots.

Keep the soil moist by watering consistently and applying some mulch. Grass clippings, comfrey leaves, hay, chopped leaves, or what else you have. Some celery varieties should be blanched for more tender, classic light colored, stems. A cardboard tube or mulch can help with that. Some people plant celery in trenches and cover the stems with soil as the celery grows. I like mine just the way it is without blanching, but for fresh eating, blanching is recommended.
Feed with compost tea or diluted fish emulsion once every 2-3 weeks. Add extra compost midway through the season.
Celery takes about 90-120 days after transplanting, depending on variety, for full size maturity. But you can harvest when you feel the stalks are large enough for use. Just break or cut off individual stalks as needed, near the bottom and from the outside, and let the inside keep growing.
The mature celery can be harvested anytime up until temperatures start dipping below freezing. Its flavor actually improves with the cold weather, but it can get frost damage in freezing temperatures. Some varieties are more frost hardy than others.

Celery can easily be frozen without the need to blanch it. Just chop into usable chunks and put them into freezer bags. You can also flash-freeze on a cookie sheet and bag once frozen solid. This way you can easily remove just what you need.
Celery root can be stored just like carrots in a root cellar, garage, or other cold, humid environment. It can keep up to 8 months that way. Store away from fruits and vegetables that produce ethylene gas.
Celery stalks will stay fresh in cold storage at 32 degrees with 98-100% humidity for 1-2 months. Chinese celery will not store long past a few days in the refrigerator. Wrap with moist paper towels or moistened paper bag.

Aphids, snails and slugs can be a pest problem. Use beer traps for slugs or spread diatomaceous earth or wood ashes around the plants. (This must be reapplied after it gets wet). Take care with the diatomaceous earth since it can also harm beneficial insects. For aphids you can try to spray them off or use an insecticidal soap.
In general, always try to resolve any pest or disease problems without spray where possible, since most sprays or powders, organic or not, can harm beneficial insects too.
To avoid leaf blight, ensure good air circulation around the plants and avoid overhead watering. Rotate celery each year.
To prevent blackheart, ensure adequate calcium in the soil and water regularly.

Seed saving is a skill all of its own and it can be a bit intimidating. I would start with just one variety. Choose the one that did the best and save the roots for the next year to produce your seed. This way you don't have to worry about cross-pollination, unless you have a close-by neighbor who also lets his go to seed. Then you can alternate varieties each year.
Seeds are produced in the second year. If your celery bolts in the first year and makes seed, don't save it. You don't want to perpetuate that trait.
Celery varieties need to be separated by a quarter mile to prevent cross pollination. Yikes!
Best thing to do, if you're trying to save more than one variety, is to cover the flower stems that you want to save seed from before the flowers open, with organza. Then you'll need to play bee and hand pollinate the flowers using a soft hairy brush. You can also try to just shake the plants whenever you walk by.
Collect seeds from 15 or more plants of the same variety for replanting (to maintain genetic diversity and prevent inbreeding). Thresh by hand or by hitting seed stalks against the sides of a bucket, then winnow to clean.

Celery can be grown in planters or grow bags. A single plant needs a pot that is one foot wide and one foot deep, filled with rich potting soil and some compost. Keep it moist and mulch the surface with pine bark or vermiculite.