If you want to sow and grow celery, you should start in good time. For both celeriac (Apium graveolens var. rapaceum) and celery (Apium graveolens var. dulce), the plants have a long cultivation period. If celery is not grown in advance, the growing season in the open field is hardly sufficient to bring in a rich harvest.
When should you sow celery?
The seedling cultivation of tuberous and stalk celery is about eight weeks. Therefore, plan enough time for pre-cultivation. For early cultivation under glass or foil, sowing starts as early as mid-January. For outdoor cultivation, sowing usually takes place from the end of February/beginning of March. Cutting celery can also be grown in pots from March onwards. As soon as no more late frosts are expected, celery can be planted out in the bed.
How to sow celery properly?
It is best to let the celery seeds soak in water overnight and then sow them in seed trays filled with potting compost. Press the seeds well with a board, but do not cover them with soil. Since celery needs light to germinate, sift sand over the seeds only thinly, about half a centimeter (0.2 in). Gently sprinkle water over the substrate and cover the tray with a transparent lid. Then place the vessel in a bright, warm place. A bright windowsill or greenhouse with temperatures between 18 and 22 °C / 64 and 71 °F is well suited. The optimal germination temperature for celery is 20 °C / 68 °F, temperatures below 15 °C / 59 °F will later encourage the plants to sprout. Until the cotyledons appear, keep the substrate evenly moist, but not too wet.
Prick out celery
To get strong, well-rooted seedlings, pricking out is very important for celery. Once the first two to three real leaves have formed, it is time to go. Using a dibber, carefully lift the plants out of the tray and shorten the long roots a little – this will stimulate root growth. Then place the little plants in small pots with potting soil. Water the plants well afterwards.
Continuing to cultivate precultivated celery
After pricking out, the celery plants continue to be cultivated in a bright place, but somewhat cooler at 16 and 18 °C / 61 and 64 °F and with sparing watering. After two to four weeks, they can be supplied for the first time with a liquid fertilizer, which is applied with the irrigation water. From the end of April, the plants should then be slowly hardened off and placed outdoors during the day. When the last late frosts are over, celery can be planted in the prepared vegetable bed. Choose a generous planting distance of about 50 centimeters (20 in). Celeriac should not be planted deeper than it was previously in the pot. Because if the plants are planted too deep, they will not form tubers.