Celeriac Secrets

January 25, 2007 · Filed Under Featured Plant 

Many people don’t know what an interesting vegetable celeriac or celery root can be. It’s delicious raw or in soups. It’s easy to save seeds from. It’s rewarding and easy to grow.

There are 3 different kinds of celery plants; normal (sometimes called blanched or bleached) celery, leaf celery (sometimes called zwolsche krul) and celeriac (sometimes called celery root). These are all three related, and will cross pollinate if grown next to each other, so you can only save seeds from one at a time. Of these, normal and leaf celery are much more difficult to grow than celery root.

The two main ‘tricks’ for growing celery root are choosing the right variety and not planting it in the garden too early.

My favorite variety is Giant Prague, but I know several others do well too. The best thing is to ask fellow gardeners and find out what kind does best in your climate. If you are experimenting with different varieties, don’t be discouraged with some failures. There are normal and ‘smooth’ types. I don’t care for the smooth type, and in any case if you do grow it be aware that it is very different from the normal kind. Smooth refers to it’s texture when eaten.

Celeriac is a biennial. This means there are two seasons that make up the growing cycle of this plant. The first season it will grow and form the roots, and the second put it’s energy into reproduction, grow a flowers stalk and go to seed. The problem is celeriac gets easily confused, and if you transplant plants out too early into cold ground, it can think it has passed through it’s first growing season and into it’s second. What usually happens then is either the roots remain very underdeveloped or sometimes they will bolt (send up a flower stalk). In either case it is usually inedible. For some reason this is often not well documented, and it can be hard to understand what is going wrong with your plants if someone doesn’t explain it to you!

Because celeriac has a long growing season, the plants are best started indoors about 7-12 weeks before setting them out into the garden. I usually set them out between 15 May and 1 June, but this will vary according to your climate.

I prefer to start the seeds in a flat (seed tray) and after they have developed their first set of true leaves (after the cotyledons) transplant them into their own containers. The reason for doing it this way is the seed is very small, and it is easier to broadcast over a tray than plant 1 or 2 seeds at a time in pots. This way also allows you to more easily select the strongest seedlings and, if you have old or unreliable seed, you can easily compensate by sowing a little more densely. When transplanting them into their own containers, the soil can be loosened with a table knife or similar instrument, and the seedlings plucked out of the dirt with your fingers. While in the tray, a bottom heat source is not necessary, but can help the seeds germinate faster. Garden centers sell special appliances for this. Make sure you keep the seeds and seedlings moist but not soggy at all times. Make sure you provide the seedlings with enough light, either fluorescent tubes or a growlight.

Once in the garden celeriac appreciates good soil, rich in organic material. It is also very important to give it sufficient water. It can be dug up in the late fall, after the roots have grown to a good size. Celeriac is not very frost hardy, but it may overwinter in mild climates.

Comments

20 Responses to “Celeriac Secrets”

  1. Marcia Bauchle on March 26th, 2007 15:04

    Thank you so much for posting this information. It is by far the best I have read in learning how to grow celeriac. I will come and read it again soon. Marcia

  2. Elaine Stewart on March 26th, 2008 8:37

    I have a neighbour who wants me to start celery root plants for him this season. I will likely plant starting next week:

    How long before you can harvest???
    We can usually plant out May 15th after last frost. Is that enough time to mature as we will likely get a frost in Sept 15th – 120 days?

    How tender is the tranplant stage? Do you have to seperate carefully and worry about destroying any roots??

    How many seeds per tray do you aim for. Around 300????

  3. Patrick on March 26th, 2008 9:47

    Hi Elaine,

    You are starting them a bit late. If you grow them again next year, I suggest starting in February. Also, the seeds are slow to germinate, expect them to take about two weeks.

    They are a little tender at the transplant stage, and if you have a lot of seeds that grow next to each other in the tray it may not be possible to separate them, but I don’t usually find this is a problem. Since you are sowing in a tray, you usually just need to look for another spot in the tray where they aren’t growing so close together. The more light the seedlings get the better!

    If your seed is fresh 300 seems like a reasonable number. Because of what I just said, you may want to make sure some parts of the tray are more densely seeded than others.

    Your season should be just long enough. If you get an early frost, the roots may be a little on the small side. The tops of the plants are easily killed by frost, but the roots are pretty frost hardy, so you may as well leave them in the ground until the tops die then dig them up and see what you get. Be careful not to set them out in soil that’s too cold. The plants are biennial, and if they bolt, are woody and underdeveloped it’s because they were confused by cold soil and thought they passed through two growing seasons.

    Also, I didn’t mention it in this post, but celeriac likes to be a little crowded in the garden. If you give it too much space, the plants develop large tops at the expense of the roots. 6″ (15cm) spacing in rows 1′ (30cm) apart is about right.

    Celeriac is a great vegetable to grow yourself. Good luck!

  4. Michele Williams on July 25th, 2008 9:31

    Please could you tell me the difference between celery and celeriac.

  5. Patrick on July 25th, 2008 13:09

    Hi Michele,

    They are the same plant, only celery is bred to have nice tops and celeriac for large roots. There is another variant usually called zwolsche krul bred for nice leaves and is used in a similar way to parsley, but the flavor is celery.

    Celeriac is most popular in northern Europe, but you can find it in the produce section of US supermarkets. It’s often used raw in salads or cooked in soups. If you’re familiar with Campbells vegetable soup, perhaps you know those white squares of celeriac it has.

  6. Jo on January 14th, 2009 22:35

    Greetings and Salutations! I am located in coastal North Carolina, 50 miles north of Wilmington. I’m growing celeriac (Giant Prague) for the first time for a local chef. I am grateful for the information you have posted here. Could you please tell me what your average last frost of the season is?

    Based on your posting, I’m going to go ahead and set up some starts for transplanting late March or early April. However, I would like to base future plantings on a frost schedule unless you have some advice to the contrary.

    Thanks again for taking the time to make this excellent posting.

  7. Patrick on January 14th, 2009 23:08

    Hi Jo,

    Thanks for the comment.

    Here in Amsterdam, our average last frost date is about May 1st. Just be sure not to rush the seedlings out into cold ground, and they’ll do a lot better.

    Good luck!

  8. Jo on January 15th, 2009 16:14

    You are very welcome. Our last frost is Mid-March so I’m tray seeding celeriac, peppers, cabbage, and cauliflower this week. We are “Wanna Be Farmers” and working on developing our plan of action so as to be as successful as possible with the greatest diversity of plants as possible.

    Finding your post has been very timely and I look forward to perusing more entries in the near future.

  9. Jo on March 2nd, 2009 16:25

    Greetings!

    The sprouts are lovely. TINY wee things. I use egg carton with only one seed per cell. Even so, some cells have 2 or 3 sprouts. I am moving them to a larger container today. Should I remove the extra side sprouts or are they actually part of the main plant?

    After moving to a larger container, they will be returned to their sunny, south facing window. I won’t plant out until April or so. Do these need to be hardened off?

    Thanks again! Jo

  10. Patrick on March 2nd, 2009 20:35

    Hi Jo,

    That’s very strange you would get more than one sprout per seed. I usually plant mine in a tray with lots of seeds sprinkled about, then very carefully pluck them out and transplant them. They really are tiny, but it is possible to do this.

    I suggest taking one of your plants and gently lifting it out of the soil If it is really all attached and one plant, then no you shouldn’t remove the side shoots. If you really have more than one plant growing per cell, then you should remove the extra plants.

    Hardening off is very important! Don’t forget to do it.

    Good luck!

  11. Jo on March 3rd, 2009 18:11

    Thanks! I doubt I’ll get it done today, but when I do, I’ll let you know. Hey, I’m old and half blind so maybe I did get in more than one seed.

    Another question, have you ever companion planted for the specific purpose of using one plant to protect another?

    We have viral issues with tomatoes because of the thrips occasioned by the grains grown in neighboring fields. I will be planting some virus resistant strains this year, but I am also going to try planting some heirlooms. The heirlooms are already 3 weeks sprouted but yesterday I added a red opal basil seed as a companion. I did something similar with my peppers planting Thai basil with the sweets and oregano with the hots. All as a “shield”. Have you heard of similar experiments?

  12. Patrick on March 3rd, 2009 19:39

    Hi Jo,

    Companion planting is a great solution for just this kind of problem! You might also consider planting marigolds together with your tomatoes.

    This is one of the problems with the way our food is grown these days, just huge fields of identical crops with no biodiversity — monocultures. When you grow different plants together yourself, it can make your garden a lot healthier in many different ways.

    When you grow different plants together, you have to make sure the plants are compatible. This is easy, just look them up on the chart near the top of this page:

    http://attra.ncat.org/attra-pub/complant.html

    In the case of tomatoes, be sure not to plant them near potato, fennel or cabbage related plants.

    On the other hand onion/garlic and related, nasturtium, marigold, asparagus, carrot, parsley and cucumber are all considered to be beneficial to tomatoes in some way.

    Good luck!

  13. Jo on March 5th, 2009 19:49

    I am so with you regarding monoculture! But then our society is a tad ridiculous regarding our feeding habits. Here is another companion planting paper: http://www.ghorganics.com/page2.html

    This is the guide I’ve been using. We have 2 acres separated into “plotlets”. We also have additional plantings along the front of the house and the “formal driveway”. The plots are annuals that we also rotate annually, there are 8 at the moment. Two will be lost due to planting them in truffle inoculated hazelnut and oak trees but another two will be created elsewhere on the property.

    The marigolds don’t work very well for us. They become infested with Japanese beetles which then move on. I prefer the beetles to eat then croak. I’m using 4 o’clocks for that. I’m burying doubled paperbags filled with topsoil at the corners of the potato patches and planting horseradish inside to ward off potato beetles. Sunflowers on one border for something I can’t recall at the moment.

    Yep, this is a great time of year!

  14. Jo on May 15th, 2009 16:41

    Hi Patrick! More celeriac issues for you! All my little seedlings croak. They kicked the bucket! SO, I direct seeded. What do you think my chances are? The soil was weeded out and in the “seam” of garden fabric to help reduce the weeds. I planted about 15′ of the row with the celeriac and the rest in beets. There are cabbages on one side and chard on the other. The chard, from seed is doing fairly well and so are the cabbages that came from purchased transplants. The chard is “unprotected” but the cabbages are planted in the fabric.

  15. Patrick on May 17th, 2009 22:33

    Hi Jo,

    I’m sorry, I skipped over this question and forgot to get back to it. Anyway, there are two issues with direct seeding celeriac. The first is it needs a really long growing season, so it’s really handy to give it a good start indoors. The second is the seeds are very slow to germinate, then very slow to grow at the beginning.

    Celeriac needs to be keep moist all the time, and can really never be allowed to dry out. While the plants are so small and tiny it will be a big battle to keep them wet enough and free enough of weeds in your hot climate.

    Anyhow, good luck, I hope you manage to get another crop going.

  16. Jo on May 18th, 2009 12:53

    Well, it has had a good start at least! The weeds have been kept out of this tiny area and it’s been an easy trick thanks to the fabric we are using this year. AND, it’s been raining like CRAZY! We had 4″ yesterday alone! Regardless, I’ll keep on that issue and thanks for dialing me in on it. There is one reseeded chia plant and one reseeded basil plant coming up in the row. That’s how well weeded it is! Wish I could say that for the rest of the garden!!! ;o)

  17. Ally on January 21st, 2010 1:01

    I planted celeriac last May 2009, i have some beautifil plants with no roots. 1. can you tell me why this happenned? 2. can we eat the greens?

  18. Patrick on January 21st, 2010 12:05

    Hi Ally,

    For celeriac the variety is very important. I’ve had the best luck with Giant Prague, but you may want to try a few different ones to see which does best in your garden.

    Also water is important, the plants need to stay moist the entire growing season.

    Finally, some years are just better than others. For the last two years here in Holland the celeriac has done miserably. If you are in the UK, or another nearby country, this may be part of the reason.

    I’m not a big fan of the tops, and you certainly can’t just eat them like normal celery. I have made soup stock with them in the past, and that worked okay,

  19. harry on February 23rd, 2010 19:17

    I’ve tried growing celeriac for the past 2 years in the UK. The roots weren’t as big as I’d expected but roasted like parsnip were delicious, so well worth trying again. One slight problem though, the slugs seemed to like them just as much as I did. Any suggestions to combat this persistent nuisance ?

  20. Patrick on February 25th, 2010 11:12

    Hi Harry,

    I don’t usually have slug problems with celeriac, actually slugs are not a serious problem in my garden in general.

    Usually the solution to slug problems is control by hand. Often you can do this by laying a board on the ground near your plants, or someplace else for slugs to hide. Then you can come by from time to time, and gather the slugs up or kill them. They are easily killed with a light sprinkling of table salt, but of course this is also toxic to plants, so use sparingly.

    Here in Amsterdam, the last two years have been really disappointing for celeriac, and as much as anything I think it’s just the weather we’ve had. I hope this year will be better!

    Thanks for stopping by and leaving a comment.

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