Popular for its crisp, refreshing stalks, celery is a grocery staple in most homes. A specific variety of celery, however, is grown for its roots, rather than the stalks. This variety is called celeriac.
Also known as celery knob, celery root, knob celery, and turnip rooted celery, celeriac (Apium graveolens var. rapaceum) tastes like a cross between celery and parsley. (That’s because celery is a member of the parsley family!) Botanically, celeriac is a biennial, but it is grown as an annual. Biennial plants generally live for two years, going to seed in the second year before dying. Celeriac is very popular in Europe, stores in the refrigerator for months, and is an excellent addition to soups, stews, salads and purées.
How to grow celeriac
Celeriac is easier to grow than celery, but it does have a tendency to bolt in hot weather. It grows best in in USDA growing zones 7 and higher. In our hot, dry region, celeriac is an excellent winter crop that is best started in late summer or early fall. Celeriac seeds are more likely to germinate if they are soaked overnight before planting. Seeds should be started indoors or in a protected area. Plant seeds no more than 1/8” deep and keep the soil moist until germination occurs by covering the soil with burlap, seed cloth, or vermiculite. Watering from the bottom of the container is preferable to avoid fungal problems. Germination should occur in 21 days.
When seedlings are 2-2 ½” tall, transplant them to a sunny location. Plants should be placed 6 to 24 inches apart. Celeriac is shallow-rooted, so use straw or other mulch around the plants to stabilize soil temperatures and reduce weed competition. The ancestor of celery and parsley was found in marshy areas, so keeping the soil moist and nutrient-rich with compost will improve crop size and flavor. Feeding young plants with fish emulsion every couple of weeks is an excellent way to make sure that they have all the nutrients they need. Lateral leaf shoots should be removed and the root shoulders should stay covered with soil to maintain tenderness.
The large root (hypocotyl) is usually harvested when it is baseball to softball size. Ideally, this is after a light frost, which converts some of the starch into sugar. Before eating celeriac, the brown outer husk is removed, similarly to jicama.
I hope this information inspires you to grow more of your own food. You can ask your garden questions on my Home page.