Although popular in Europe, celeriac has yet to “take root” in American gardens and kitchens—something we hope will soon change! A descendant of the same wild ancestor as celery, celeriac develops small, green stalks aboveground but has been bred to dedicate most of its energy to the development of large, tasty, bulbous roots. This root has been described as having a lovely flavor of celery mixed with a touch of parsley and is extremely versatile as it can be baked, broiled, fried, or even eaten raw. A cool-season biennial, celeriac can be grown as an annual as long as it’s planted at the proper time.
As the Dutch are particularly fond of celeriac, it’s no wonder the most popular variety of this veggie—the Diamant—was developed in the Netherlands. This hybrid is favored for its uniformly shaped roots that tend to grow slightly aboveground, making for easier harvests. Diamant celeriac also tends to develop less side shoots, allowing more energy to be sent to the root, and stores longer than other varieties: up to 6 months!
Seed Depth: 1/8–1/4″
Space Between Plants: 6–8″
Space Between Rows: 12–14″
Germination Soil Temperature: 70–75°F
Days for Germination: 14–21 days
Sow Indoors: As celeriac requires a long period of growth, starting your plants indoors is recommended as it will allow your seedlings time to develop without over-exposing them to the cold. Can be started indoors as long as 10 weeks prior to the average last frost date.
Sow Outdoors: Transplant seedlings into your garden when temperatures are consistently above 45°F. If seedlings are exposed to temperatures below 45°F for more than a week or so, the plant will begin to think it’s in its second year of growth, devoting energy to leaf instead of root development.
Vegetative: Can be grown via cuttings; however, as this plant isn’t very common in the US, cuttings can be difficult to obtain.
A Native of the Mediterranean, celeriac is relatively frost tolerant but prefers temperatures of at least 45°F during the day, especially in its earlier stages of growth. In its adulthood, it’ll do well with some slow hardening-off, so timing your planting so that days are warm and nights are cool as the plant reaches maturity is key. Celeriac is a plant of moderation, so keep soil moist if living in an area with little precipitation, keep plant partially shaded if living in an area with intensely hot summers, and keep stalks covered if living in areas with cold springs and falls. If living in USDA Zone 7 and above, celeriac can be planted in the late summer/fall for a winter/spring harvest.
Natural: Prefers full sun but will tolerate partial shade in extremely hot weather.
Artificial: When starting seedlings indoors, plants will require at least 8 to 12 hours of lighting. An HID lighting system will provide adequate heat and light to help your seeds germinate. Keep lights approximately 2–3′ from the top of plants to prevent burning.
Soil: Will grow best in loamy soil, rich in organic matter that drains well but retains moisture. Will tolerate soil that is somewhat sandy or rich in clay as well. A soil pH of 6.0 to 7.0 will keep plants happy and healthy.
Soilless: Seeds will germinate in most soilless mixes but prefers a mix that contains coco coir and perlite.
Hydroponics: Will thrive in most hydproponic systems but does particularly well in ebb and flow systems.
Aeroponics: Although possible, there’s little information available on growing celeriac aeroponically. So, if you end up giving it a try, let us know how it turns out!
Water: Requires moderate levels of water. Keep soil moist but not soggy to avoid bolting.
Nutrients: A relatively heavy feeder, providing your plants with compost or fertilizer every two to three weeks and prior to planting will help your plants grow. Avoid giving plants too much nitrogen as this can encourage leaf growth instead of root development.
Foliar: A seaweed extract foliar applied every three to four weeks can help your plants thrive.
Pruning: Cut back dead or weak-looking leaves. Once roots have started to show above the soil, side shoots may start to develop. These should be cut off to help the root continue to develop.
Mulching: Applying mulch to young plants can help keep them warm in cooler weather. Cover roots as they start to appear above the soil surface with a light, organic mulch such as straw or leaves to prevent discoloration from the sun.
Deficiency(s): Cracked stems can be a sign of boron deficiencies. Applying a boron-based fertilizer can relieve your plants of this issue.
Rotation: Rotate with brassica crops each year to keep soil healthy and pest free.
Companions: Grows well with lettuce, peas, spinach, onions, tomatoes, broad beans, and nasturtiums. Avoid planting with squash or cucumbers.
Harvest: Can be harvested when roots have reached 3–4 inches in diameter. Alternatively, plants can be left in the ground and covered with a layer of straw until ready for use if cold weather is on its way. To harvest, pull on the greens gently to extract the root from the soil. Shake off excess dirt and cut greens an inch above the root.
Storage: One of the best things about celeriac is that it stores very well. Keep cool in a root cellar or cold basement for up to six months. Will keep in the refrigerator in plastic bags for a couple of weeks if the greens are removed.
History: Celeriac wasn’t a popular vegetable in the human diet until the Middle Ages. That said, this strange looking veggie wasn’t entirely unknown before then. In fact, celeriac was mentioned by its Greek name selinon in Homer’s The Odyssey, growing at the nymph Calypso’s home. If the immortals loved this vegetable, we’re sure you will too!
Preserve: Will keep well without much effort in cool, dry spaces. Celeriac root can also be pickled in a vinegar-based solution. Take note that it doesn’t freeze well.
Prepare: To prepare this veggie, wash thoroughly to remove all dirt and cut off the root end. Peel off the tough outer layer and cut into smaller chunks, which can be eaten raw or cooked in all manner of ways. It can be boiled, baked, fried, sautéed, pureed, you name it! Many recipes suggest turning this root into a tasty mash in place of mashed potatoes. If not using the entire root immediately, rub the exposed side with a lemon to prevent discoloration. The leaves may also be eaten raw or cooked as you would spinach.
Nutritional: Not only great tasting, celeriac is also a super healthy veggie. It’s low in calories but high in fiber and contains vitamin(s) K, C, and B-6 as well as the minerals phosphorus, calcium, iron, copper, and manganese. Also contains antioxidants.
Medicinal: Some studies have suggested that celeriac may contain compounds that can prevent certain types of cancer such as colon and leukemia. Its high content of vitamin K has also been linked to increasing bone mass and helping prevent osteoporosis.
Warnings: Some folks may suffer from an allergy to celery and in turn, celeriac. If you have an allergy to celery, avoid consuming this vegetable until speaking with a health care professional.
If this simple yet delicious Celery Root and Apple Soup recipe doesn’t have you convinced to add this plant to your garden, we don’t know what will! As the recipe suggests, try toasting some homemade bread to go along with this dish for a filling and fantastic winter meal.