Apium graveolens var. rapaceum
Herb - Culinary
USDA Zones 3 to 7
Soil pH 6.0 to 7.0
Companion Plants. Cabbage - Tomatoes
Celeriac also known as celery root, is a close relative of celery, but is grown for its crisp tasty roots rather than its stalks. It has a taste similar to celery with a subtle fruit - nut like Flavor.
Celeriac is biennial and is much easier to grow than common celery. It is very common among Europeans but not very well known in North America. It's not a very attractive or visually apealing vegetable, the roots are knobby and have an unsightly mass of hairlike rootlets popping all about. The taste however is different and delightful. It has a relatively long storage life of 6 - 8 months raw.
Unlike its close cousin celery, celeriac is not difficult to grow.
It has a growing season of about 120 days as well as a relatively long germination period of 2 - 3 weeks. Before planting your seeds, be it in pots or directly in the garden it is a good idea to soak them overnight in luke warm water, not hot, just luke warm or slightly above room temperature water. A few drops of fish emulsion mixed in the water wouldn't hurt either. The overnight soaking will help expedite germination.
Harden off seedlings prior to transplant by slightly reducing water, and keeping them outdoors for gradually longer duration's each day, bring them in at night. This process should last at least a week.
Celleriac is biennial, when seedlings experience extended periods below 40 - 45 F the plants cycle is thrown off. They go into their second year mode, having already experienced what they believe was a winter and rebirth in spring. In this scenario their energy is devoted to producing flowers to perpetuate their species - not roots. They need temperatures of at least 65 - 70 to avoid this.
The plant matures rather slowly, leaving many gardeners with the feeling that their crop is failing. Towards the end of the summer /early fall however it grows by leaps and bounds.
Reducing competition from weeds is of course a good idea.
Fertilizer is important for celeriac, adding a heavy mix of fertilizer, compost or manure to the soil before you plant is advisable. I also like to add some diluted fish emulsion once weekly.
During the growing season you should remove some of the outer leaves to force more energy into root development - don't get carried away, just a light periodic pruning. Also remove any yellowing leaves from the lower part of the crown. check for any lateral leaf shoots which should be pruned away to encourage crown and root development.
Harvesting the roots late in the season after a light frost is best.The frost leads to a crisper and tastier root. The frost helps the plant convert its starch to sugars. The roots can also be left in the ground and harvested as needed, or stored in moist sand in boxes. In very cold regions indoor storage is necessary.
Shake off excess dirt and root fibers and most of the foliage before cleaning the root with water.When the water has dried place the roots in plastic bags or containers with air holes for storage.
Storage temperature for celeriac is 35 to 40 F, a refrigerator works well if you don't have a root cellar.
It's primary adversaries from the insect realm are parsley-worms, Celery worms, Cutworms, carrot rust flies, and nematodes. Sometimes slugs, aphids and white-flies.