Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
What is Celeriac?
Celeriac (Apium graveolens var. rapaceum) is a biennial plant that is grown as an annual. It is closely related to celery but easier to grow and store. Celeriac is native to the Mediterranean region and is very popular in the cuisines of Europe, although less so here in the US.
The reason that it got its nickname, celery root, is because it is the hypocotyl rather than the stalks that is eaten. The hypocotyl is the area of the stem that is below the foliage but above the roots. In the case of celeriac, the area is swollen. To prepare it for cooking, the roots and stalks are cut off. Then the hypocotyl is cut in half. Lay the hypocotyl on a cutting board, flat side down. Using a peeler or paring knife remove the bumpy skin. What is left, tastes similar to celery. It can be blanched, stewed, roasted or mashed. It can also be used in soups and casseroles.
How to Grow Celeriac
Growing celeriac is a lot like growing celery. It needs moist rich soil similar to the habitat of its native home in marshes. It’s a good idea to work some compost into the soil to enrich it before planting the seedlings that you started indoors. Celeriac is not readily available as transplants at nurseries here in the US, so most gardeners grow it from seed.
Another good idea is to dig the same trenches between your rows that you dug for your celery to allow water to pool between waterings, helping the soil to stay moist. A thick layer of mulch will also help the soil to retain moisture as well as prevent weed seeds from germinating. The weeds compete with your plants for water and nutrients.
Plan on giving your celeriac a minimum of 1 inch of water per week. Don’t let the soil dry out. And don’t worry about your plants getting too much water if you are having a rainy summer. They are descended from marsh plants so unlike a lot of other vegetables, they actually like lots of water.
All of that watering could leach nutrients from your soil. Fertilize your plants every two weeks. I prefer to use compost but you can use 5-10-10 fertilizer if you like.
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How to Grow Celeriac From Seed
Celeriac has a long growing season, 120 days, so you will want to start your seeds indoors. The seed coats are hard so you will need to soak your seeds overnight to soften them and make germination easier. Surface sow your pre-soaked seeds in containers with pre-moistened soil 10 weeks before your last frost. Don’t cover them with soil. They need light to germinate. I always water my soil before I sow seeds, especially seeds that are sown on the surface. I’ve found that if I plant my seeds and then water, the soil and the seeds wash away and I have to start over.
Keep the soil moist and warm. 70⁰F is ideal. A heat mat will help. You will need to be patient. The seeds will take 2 – 3 weeks to germinate.
You can transplant your seedlings outdoors when nighttime temperatures are above 45⁰F. Space them 8 inches apart in rows that are 18 inches apart. Don't forget to dig your trenches to catch and store water to keep your plants moist.
How to Harvest Celeriac
Celeriac is usually harvested when the hypocotyl is 4 – 5 ½ inches in circumference. If you prefer, you can wait until after the first frost to harvest your plants. The cold temperatures turn some of the starch in the hypocotyl to sugar, improving the taste. To harvest, simply grasp the stalks and pull the plants from the soil, roots and all.
How to Store Celeriac
Celeriac is good for long term storage. It stores best at temperatures between 35⁰F and 40⁰F with high humidity.
After harvest, cut off all of the foliage leaving only about one inch. Trim the roots to one inch also. Gently brush the soil from the hypocotyl, but don’t wash it off. The added moisture will cause your celeriac to rot before you have a chance to use it. Place the remaining hypocotyls in a mesh bag or food grade perforated plastic bag.
Store the bag either in the crisper drawer of your refrigerator or in a root cellar. They can be stored for 6 – 8 months.
© 2020 Caren White