Plant Growth Habits, Seasonal Eating and the Optimal Time to Eat Each Vegetable

By Tom Cowan, M.D.

The other day at the local food co-op, and I noticed the woman in front of me in the check-out line purchasing a plastic container of cherry tomatoes. I thought to myself, “it's wrong to be eating fresh tomatoes in the middle of March!”

Tomatoes are a heat- and sun-loving plant; they die if exposed to even a touch of frost, whereas kale not only survives a hard frost, it actually thrives in cold weather. This got me thinking about plant growth habits, seasonal eating and the optimal time to eat each vegetable.

The question is, how do some plants survive freezing temperatures while others cannot? The answer seems to be that some plants are able to structure their internal fluids (i.e., water) in a form that is recoverable after exposure to freezing temperatures.  The way plants do this is similar to how one would make Jell-O. Jell-O is made by combining certain proteins and water, in addition to a catalyst. In the case of Jell-O, the catalyst is heat. The heat unfolds the proteins, they interact with water, and the water becomes gel-like when the mixture cools. Almost no matter how low the temperature gets, Jell-O will stay in this gel state.

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In plants such as kale, proteins interact with intracellular water and create a gel-like state. Absent this process, the water would instead freeze, and the ice crystals would kill the plant. This is what happens with the tomato plant. Kale and other members of the brassicas family make these proteins, which protect their intracellular water from freezing. As a result, when the temperature warms again during the day, the plant is able to fully recover.

An important point from a nutritional perspective is that these “antifreeze,” “structuring” proteins not only protect the plant, but they also protect us from disease. We have evolved to use the plant’s defense system in our own disease prevention, and this is a perfect example of seeing this system in work.  The best time to harvest kale is at the end of winter and into early spring. The kale leaves are full of nutrient-rich proteins and flavonoids that it used to protect itself during the winter. In contrast, the tomato plant develops its nutrients, like lycopene, during the heat of summer. Optimal nutrition is more than a list of which vitamins are contained in which food. It involves reading the book of nature and getting an understanding of how minerals, plants, animals and humans interact.

Our Kale Powder was made with spring-harvested, nutrient-rich leaves. Picked at their optimal time, they are lightly cooked, then dried to seal in the valuable nutrients. Please see our recipe section for the myriad ways to enjoy our Kale Powder.