Marion Owen

Lydia Clayton, Agriculture and Horticulture specialist with the UAF Cooperative Extension Service, shares winter gardening, soil care, and root cellaring tips with a group of local growers. (Marion Owen photo)

When asked if eating home-grown kale could be as dangerous as eating a nitrate-laced hot dog, Lydia Clayton didn’t skip a beat. In fact, she used the opportunity to teach us something about winter vegetable gardening that we’d never considered.

Originally from Oregon, Lydia Clayton knows a thing or two about gardening in a cool, moist climate. Kodiak took her by surprise. “It’s 50 degrees today. It feels like the tropics.”

Lydia Clayton, wearing her Cooperative Extension Service agriculture and horticulture hat, traveled from Kenai to Kodiak last week to teach workshops, meet hoophouse growers and other farm and agriculture folks, and generally get a feel for the community. “There is a lot happening around Kodiak. I’m impressed, and I can see why bringing back an extension agent would be helpful here,” she told the audience attending her “Sowing, Raising, Sustaining,” workshop, which was sponsored by the Kodiak Soil and Water Conservation District.

Dressed in a plaid shirt and jeans, Lydia covered several topics in the noon workshop, starting off with tips for extending the growing season into the fall and winter. The technique is relatively new for northern growers and made possible with the use of row covers, hoophouses (high tunnels) and smaller hoop setups.

“Not everything works well, planted in late summer with the idea of it growing well into the fall,” said Lydia. “Winterbor kale, for example, does great, while Russian red kale wilts and shrivels in the deep cold and reduced sunlight.”

“When the daylight dwindles to six or seven hours, veggies are sort of suspended in growth. I like to think of them as staying in place for harvesting.”

When the temperature dips to freezing and below, Lydia recommends adding another layer. “Draping row covers over crops insulates them with a pocket of air, sometimes with eight degrees of protection, like a house inside a house.”

With the decrease of light however, there is an increase in potential problems with nitrates. “In the fall when growing processes slow, plants are still taking in nutrients and concentrating nitrates. In the summer, this isn’t a problem because the plants are using the nitrates up in the natural process of photosynthesis. And when we eat veggies, our bodies process the nitrates just fine.

“But when photosynthesis slows, like in the fall and winter, nitrates concentrate in crops like arugula, radishes and kale.”

After Lydia introduced the nitrate issue, hands shot up. One person asked, “Is this the same nitrates you find in hot dogs? Should we avoid this somehow?”

Lydia went on to explain how our organs filter nitrates, but that babies should avoid vegetables high in nitrates since high nitrate levels can cause a type of anemia.

After the workshop, I headed to my computer to do a little research about nitrates and nitrites in our diet. I found a great article in the San Francisco Gate by Suzanne Robin called “Sodium Nitrite in Vegetables.” Suzanne is a registered nurse with over 25 years of experience and has coauthored and edited numerous books for the Wiley “Dummies” series.

“Many vegetables contain sodium nitrate, a small percentage of which converts to sodium nitrite after you eat it,” says Suzanne. “Sodium nitrite can form nitrosamines, a potential cancer-causing agent, in the intestines.”

Here’s the deal: In most cases, eating vegetables is not considered dangerous in the same way that eating processed foods is. For one thing, vegetables contain antioxidants that prevent the formation of the nitrosamines.

But what about the garden and what goes on in the soil? Suzanne goes on to say that soil contains sodium nitrate, which is necessary for plant growth. “Soil organic matter naturally contains around five percent nitrogen. Microorganisms in the soil change nitrogen to nitrate so plants can use it. Animal manure, chemical fertilizers and treated waste also add nitrogen to soil.” Confirming what Lydia shared with us, plants absorb sodium nitrate from the soil.

It was interesting to learn that young plants generally contain more sodium nitrate than mature plants, and some vegetables have higher nitrate levels than others. And it makes sense that different soils have different nitrogen content, which affects the amount of nitrate in the plants. And while it’s important to replace what nutrients plants take up by adding compost, kelp, manure and other inputs, fertilizer use can also affect the amount of nitrate in vegetables.

So here are a couple general guidelines: Green leafy vegetables and root plants contain the most sodium nitrate. Vegetables high in sodium nitrate include beets, cabbage, carrots, celery, radishes and spinach. According to the University of Minnesota Extension Service, “Around 90 percent of the nitrite in your body comes from vegetables, while just 10 percent comes from processed meats.” “Normally, sodium nitrate in vegetables does not pose the same health risk as nitrites found in processed meat,” says Suzanne Robin. While the nitrosamines have shown cancer-causing potential in animal studies, “nitrates and nitrites themselves do not have cancer-causing potential,” she says. “Vegetables contain ascorbic acid, a form of vitamin C and an antioxidant which helps prevent nitrosamine formation, although it might not completely prevent it.”

Suzanne suggests storing fresh cooked vegetables high in nitrates for no more than one to two days in the refrigerator or cook only as much as you plan to eat at one time.

Meanwhile, back in the garden, Lydia says to not let nitrates scare you. To prevent nitrate buildup in late-growing vegetables, she shared an easy solution: “On sunny days,” says Lydia, “we recommend pulling off the row covers so the plants can photosynthesize and lower nitrate levels.”

And we all know Kodiak has its fair share of sunny days.

Recipes and gardening tips are featured in Marion Owen’s 2014 calendar: “Flavors of Kodiak Island.” Read Marion’s latest blog postings at Connect with local gardeners on the Kodiak Growers or the Sustainable Kodiak Facebook page. Archived copies of Marion’s columns are posted at Contact Marion at

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