Candy carrots and turnip treats: why some veggies are sweeter in winter

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What do winter tomatoes and summer carrots share in common? They’re boring and starchy because they’ve been grown in the wrong seasons. Frost-kissed carrots, on the other hand, are incredibly sweet and satisfying. Why the difference? You can divine the answer in a bag of potato chips.

Sugar Sticks!

Sugar Sticks! Harvested January 10th.

 

Have you ever found a brown potato chip? This occurs before the chip ever makes it to the bag, often due to a process called “chill sweetening.” Potato tubers are still alive after harvest – you know this if you’ve had them sprout in your pantry or turn green, accumulating bitter and toxic saponins. Store potatoes in temperatures that are too cold, however, and they’ll start converting their starches to sugars. These simple sugars brown during frying, producing unattractive chips that consumers don’t like. Although you may like the sound of a sweeter potato, it can be a big problem for potato farmers, as entire harvests of potatoes that don’t “chip” well can be rejected by the food processor. What’s more, remember that potatoes are a warm-season crop; any meager sugar conversion is offset by the presence of other substances that react with the simple sugars when cooked to form bitter (and even carcinogenic) substances like acrylamide.

We may prefer starchy potato tubers, but root crops should be sweet and crisp. We want chill-sweetening to occur in root crops, as well as brassicas and greens, as the shift from carbohydrate stores to simple sugars is desirable for these plants. I like to think of it is as Nature’s antifreeze. The accumulation of simple sugars helps protect the plant tissues from freeze damage – although it isn’t everything that plants need to tolerate the cold, it sure is my favorite part! Plants also begin accumulating special freeze-resistance proteins (called “antifreeze proteins” by scientists) and alter the composition of their cellular membranes to withstand freeze stress. All of these changes take some time, which is why even cold-tolerant plants can be injured if a shift in temperature occurs too quickly.

There's no bitterness to these greens, harvested December 21st.

There’s no bitterness to these greens, harvested December 21st.

 

How much difference does the right temperature make? A colleague of mine conducted rutabaga research for several years (not for food, but as a potential biofuel). During the first few years of the study, his research group grew increasingly frustrated that their plants never approached the sugar content published in the rutabaga literature. Their plants were apparently healthy and happy, growing incredibly tall, but the roots, although large and busting out of their pots, remained woody. A chance conversation with a farmer revealed their problem – they had been growing the rutabaga in a hot greenhouse, rather than out in the cold. Once they switched to cold growing conditions, their rutabagas sweetened right up.

Don’t care for turnips, beets, broccoli, or rutabaga? Perhaps you haven’t tried them “in-season” from a winter garden. Imagine if all you ever knew about tomatoes was what you had tried from a winter grocery store. Missing out on chill-sweetened root crops would be a similar travesty.

No wonder root crops, like these turnips, aren’t as common in gardens as the ubiquitous tomato or sweet corn… most people try them at the wrong time!

No wonder root crops, like these turnips, aren’t as common in gardens as the ubiquitous tomato or sweet corn… most people try them at the wrong time!

 

As you plan your summer garden, adjust your planting dates for roots crops so that they mature in fall and winter. In my plant hardiness zone (6b), I plant my root crops over the Labor Day weekend, then protect them from later hard freezes by covering with low tunnels or mulch. With a little planning, you can harvest sweets from your garden through all four seasons, looking forward to the harvest of that first frost-kissed carrot just as much as your sun-warmed tomatoes.

 

Additional Winter Gardening Resources:

These books are in my personal library, and I highly recommend them (these affiliate links cost nothing extra to you, but generate advertising fees that help me support this blog):

 

Web-based Resources

Not sure about your plant hardiness zone? Find out what it is here: United States and Canada

What could you be growing this winter? Check out this extensive list: my Winter Vegetable Planting Guide. And for more winter gardening resources from me, including how to build an inexpensive low tunnel, click the winter gardening tab above.

17 Comments

  1. charlotte

    January 14, 2013 at 8:09 am

    I know root crops grow in the winter but never realized this made them sweeter. Thanks for the info.

    • Ma Hubbard

      January 14, 2013 at 10:57 am

      Thanks! I’m hoping to try that Orange Jam recipe you posted a few weeks ago, by the way!

  2. Pat Wykle

    January 14, 2013 at 10:43 am

    hello cathy i really enjoy the comments .. have learn some important points …. keep up the good work…..

    • Ma Hubbard

      January 14, 2013 at 10:53 am

      Thank you!

  3. Jenny Williams

    January 17, 2013 at 9:16 pm

    This was absolutely fascinating and beautifully written. Looking forward to trolling the rest of your blog and reading future posts! Thank you so much!

    • Ma Hubbard

      January 18, 2013 at 10:00 am

      Thank you, Jenny!

  4. Stephen Andrew

    November 14, 2013 at 7:26 am

    I found you via hometalk and just want to commend you for posting something with actual, correct information!! Some of the gardening posts on there make me a little crazy as they have weak and/or incorrect information! I’m excited to read through your blog later when I have more time!

    • Ma Hubbard

      November 14, 2013 at 12:31 pm

      Thank you for your feedback, Stephen! I’m glad you noticed, as there is nothing worse than investing time and money into something and failing because of bad information. I spend a LOT of time researching and experimenting before I ever write a post — I’m happy to hear that it is appreciated. Have a wonderful day!

      • Mcknight, A.

        January 4, 2014 at 12:07 pm

        My family and I’s goal for this year is to grow our own vegetables, this is definitely helpful. I am a newbie to everything that pertains to growing your own vegetables and I am bookmarking your article! we live in NW FL, and temperatures drop and rise out of nowhere, like today it will get to 27 degrees at night! WOuld you recommend we start our vegetable garden right now or wait until later? I am still researching what we can plant and what we can’t. It will definitely take a lot of research for me as well! Thank you for this information

  5. franquarles

    November 17, 2013 at 10:30 pm

    Are there certain varieties of these plants that work best?

    • Ma Hubbard

      November 18, 2013 at 5:46 am

      Thanks for your inquiry. I have a list of recommended plant varieties in my table, “Winter Vegetables and Their Planting Dates,” that you can find in this Winter Gardening post. Have a beautiful day!

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  9. JimB

    December 3, 2014 at 10:05 am

    I planted heirloom carrots in late September in a raised bed. They have sprouted & are up a couple of inches. What’s your best guess for a harvest time? Are they likely to survive the winter for early spring harvest? I am in zone 8, east of Atlanta.

    • Cathy

      December 4, 2014 at 3:57 pm

      Thanks for your question. Some carrot varieties take longer to mature than others, so I can’t say for sure about yours (Do you recall the variety?). My best guess is that they won’t get to any appreciable size until late February, since they were planted so late in the season (I can’t plant carrots any later than Labor Day and expect them to get good-sized here in Kentucky). They should definitely survive the winter, however, even without protection in your zone. You can still harvest baby carrots if you’d like, however. I personally love baby carrots roasted in the oven, especially when about half-an-inch of the green top is left on — it’s edible and delicious!

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