Garden The Amazing Brassica Oleracea
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harles Darwin began his famous book, On the Origin of Species, with a chapter on artificial selection. In order to help readers understand and accept the slower process of natural selection, he documented man’s efforts to change plants and animals through selective breeding. He wrote: “If man can by patience select variations which are useful to him, why should not variations useful to nature’s living products often arise, and be preserved and selected?” Among the most astounding examples of artificial selection in the plant kingdom is the human ingenuity applied to the wild cabbage, Brassica oleracea. In the wild, B. oleracea is a weedy little herb native to the limestone outcroppings of the Mediterranean region. Over the last 2,500 years clever farmers have transformed this wonderful species into several lineages, each amplifying distinct parts of the plant. Selecting for leaves produced kale and collards. Focus on the terminal bud led to cabbage. Lateral bud selection led to Brussels sprouts, expansion of
BY L A R RY ALLEN N.C. Cooperative Extension Service Master Gardener Volunteer
20 | SAND& PINE MAGAZINE October/November 2021
meristem tissue produced kohlrabi, and most recently, a selective focus on the inflorescences led to broccoli and cauliflower. These changes occurred over centuries and across Europe. The ancient Greek writer Theophrastus mentions several leafy varieties of kale and collards in his Enquiry into Plants. By the 12th century farmers had made the jump from leafy varieties to headed cabbage by greatly enlarging the size of the terminal bud, with large leaves packed tightly around a short, fat stem (core of the cabbage). A century later, clever Belgian farmers had transformed the axillary (lateral) buds into what we now call Brussels sprouts. Expansion of the meristem led to the kohlrabi, which in stores has been cut from the leaves making it hard to imagine its relation to kale. Finally, expansion of the flowering head (inflorescences) has led to an amazing variety of what we call broccoli and cauliflower. This process began in Italy in the 16th century and continues today with amazing hybrids such as broccolini. Through all of this diversity, these descendants of the remarkable B. oleracea have retained the cold hardiness which makes them so suitable for early spring and fall plantings in Sandhills gardens.
