What? Broccoli, cauliflower and Brussels sprouts are the same plant?

Jeff Burbrink

Two weeks ago, I wrote about the ability of some members of the cucurbit family of plants (melons, squash, pumpkins) to cross pollinate. I had many responses, and some people asked if other garden plants can cross pollinate. The answer is “Yes!”

Many of our vegetable plants come from the mustard family, or Brassicaease, which contains 338 known genus and more than 3,700 species worldwide. One of the subgroups in that family is the genus Brassica.

While the genus Brassica is a large group by itself, I will focus on three particular species of this genus that provide much of our food:

n B. oleracea (e.g., kale, collard greens, cabbage, Brussels sprouts, kohlrabi, broccoli, cauliflower),

n B. napus (e.g. rutabaga, rape)

n B. rapa (e.g., turnip, Chinese cabbage, bok choi)

All of these plants can cross pollinate within their species. For example, kale, kolhrabi and brussel sprouts can cross pollinate with each other because they are all oleracea species. Turnips and Chinese cabbage can cross pollinate also. However, kale cannot cross pollinate with rutabagas or turnips, because they are a different species. The fact some plants can cross pollinate does not affect the taste or the look of this year’s plant. If the seeds were saved, the offspring would be some odd combination of the two parents, and may or may not be very desirable.

The development of these plants is an incredible story. Just look at Brassica oleracae, a single plant which humans have been breeding through artificial selection for hundreds of years. In the original form, it is a weedy little plant growing between rocks in the Mediterranean. By selecting and breeding the plant for bigger leaves, or larger buds, or better taste, at least 7 different looking plants, sharing the same scientific name, Brassica oleracae, are fed to people all over the world.

Kale and collard greens were the first to be domesticated, probably before 300 B.C. In the 1200’s, red and green cabbage was selected from kale plants for its large terminal bud. Brussel sprouts appeared at the same time, bred for their tiny cabbage-like buds that grow along the stem.

Kohlrabi, the odd looking plant sometimes call a German turnip, first appeared in the 1400’s, selectively bred from kale for its thick round stalk. Broccoli came about in the 1500’s, again from kale, and was selected for its larger flower stalk, which are harvested before the plant flowers. A hundred years later, cauliflower was developed from some broccoli varieties, focusing on the flower buds once again.

This fascinating story, spanning more than 2000 years, shows that humans have been tinkering with the genetics of our food for a long time. While some people are very concerned about genetically modified organisms (GMOs), I will contend these new lab techniques are just a way for us to do the same thing our ancestors did, but in a more precise, direct, and faster way.

In fact, if you really think about it, even plants that are labeled “non-GMO” really are GMOs, even heirloom varieties. No plant we cultivate in 2019 has avoided human tinkering. The term GMO is not really a very accurate label.

Jeff Burbrink is Extension Educator, Purdue Extension Elkhart County. He can be reached at 574-533-0554 or jburbrink@purdue.edu.

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