Apium graveolens var. rapaceum ‘Ibis’

A short entry by work-learn student Tamara Bonnemaison today. She was also the photographer.

Last week I woke up to the first frost of the year, and decided it was the perfect time for a morning stroll through UBC Botanical Garden. Walking through the Food Garden, I was reminded of the feeling of surveying my small farm after a frost, feeling at once relieved that the busy season was over, and disappointed at the loss of income that a frost represented. Now that I am a student, I can walk through a garden and focus instead on the pattern of ice crystals kissing the edges of leaves, and wonder at the biology that allows some plants to withstand freezing while others succumb at the slightest dip in temperature. This celeriac, Apium graveolens var. rapaceum ‘Ibis’, looked like it was only gently touched by the frost, and the knobby stem will remain delicious for many cold months.

Celeriac, also called knob celery, is a type of celery grown primarily for its flavourful knobby hypocotyl (stem below seed leaves), leaves, and roots. It is cultivated in temperate vegetable gardens and farms around the world, but is most popular in Europe. Celeriac requires a long growing season, and the taste of its gnarly-looking stem sweetens after a frost, making it perfect for wintery dishes such as these recipes for remoulade and soup. I haven’t yet tried these, but they look particularly delicious.

Celeriac has a number of the qualities that allow it to survive and stay tasty in cold weather. A report by the FAO discusses frost physiology in common vegetables, and Apium gravoeolens var. rapaceum exhibits a number of the traits that the FAO lists as ways that plant species tolerate cold temperatures. For example, the large, fleshy stem has a high heat capacity, preserving the day’s heat well into the night. Also, the entire plant is able to gradually “harden” by increasing concentrations of solutes such as sugar to lower the freezing temperature of its tissues. All that is to say that it is very convenient that starchy root vegetables such as celeriac achieve their peak late in the season, just in time for the thick soups and comfort foods that feel so good to eat in the winter.

Apium graveolens var. rapaceum 'Ibis'
Apium graveolens var. rapaceum 'Ibis'

9 responses to “Apium graveolens var. rapaceum ‘Ibis’”

  1. Clayton Oslund

    Very interesting photos. I have been intrigued by Celeriac, but never tried it. Now I will. About the killing of plants by freezing, I have studied that several years ago while working at a cold hardiness project at the University of Minnesota. There I learned that cold temperature does not kill plant cells, but ice formation in the cells kill the plant. Simply put, it is the permeability of the cell membrane that will allow water to leave the cell leaving the natural sugars, etc. to lower the freezing point of the internal cell, thus not allowing ice crystals to form and damage the internal cell contents. This is a simple explanation, but fascinating.

  2. Alison Place

    We often cook with celeriac in the winter, although we’ve not had success growing it in the shallow raised beds we have, or in our heavy clay. (Must try again, though.) However, a common German veggie dish for us is boiled carrot coins and celeriac cubes, done with a bit of sugar and some vinegar, as I recall. Lasts well for leftovers, and is a classic ‘winter veg’ combination.

  3. Nan Gregory

    This is a beautiful posting. Tamara, you write beautifully. I look forward to more from you.

  4. michael aman

    I echo Nan above. Thank you.

  5. Robin Day

    That comment about the plant retaining heat into the evening is exactly what I found with Diapensia lapponica cushions or clumps or domes. It was published in Canadain Field Naturalist and the dissertation was submitted at Memorial U. Newfoundland and Lanrador.

  6. Tamara Bonnemaison

    Thank you Clayton and Robin, for more information about freezing and plants.
    I am reminded of winters in the Okanagan, where farmers have ‘frost alarms’ that wake them in the middle of the night, so that they can turn on their frost fans. Those without fans will often run their sprinklers during cold snaps; the small amount of heat that water generates as it freezes is often enough to protect early blossoms.

  7. Peony Fan

    Great photos, especially the one of the crown and the leaves. Our community supported agriculture (CSA) farm gives us celeriac despite the relatively short growing season here in the upper midwest (MN). Thanks for this post.

  8. Marika Drier

    Beautiful and informative article Tamara. I enjoyed the feeling of experiencing the frosty morning and pondering this plant with you. I enjoy your writing as well. 🙂

  9. Pat

    My favourite celeriac dish is simply cubed celeriac, mixed with chopped celery stems, oil and celery salt (which is made with the seeds) and roasted on a shallow roasting tray.
    Very nice raw when young, grated and served in a salad dressing.

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