Brassica olearacea: a Many-Splendored Plant

Every hear of Brassica oleracea? Maybe you’ve heard of some of its more common names: “cabbage, broccoli, cauliflower, kale, Brussels sprouds, collard greens, Savoy cabbage, kohlrabi, and gai lan.” When I learned that all of those vegetables came from one species of plant, I was shocked! Also, fascinated, which brings me to this blog post.

First, let’s talk a little bit about natural selection. Imagine you had a plant you liked to grow because its leaves were tasty. You picked some of the veggies all season, but at the end of the growing season, you’d need to grab some seeds to use next year. You’d probably grab the seeds from the individual plants that had the biggest and tastiest leaves.

The following year, you grew only the plants with the biggest and tastiest leaves, although there’s some natural variation. Most were pretty good, but some were not very good, and some had even bigger and tastier leaves. You grabbed some seeds from the individuals with the bigger and tastier leaves to grow next year. Over many years like this, you’ll have a plant with bigger and tastier leaves than you originally had, that may not even look a whole lot like the plant you started with.

We call this a cultivar. A cultivar is close enough to the original that it’s not a separate species, but different enough that it can produce a whole different vegetable to eat.

For example, around the 5th century BCE, people started preferring the leaves of B. oleracea, so they started selecting seeds from individuals with bigger leaves. This led to the development of the cultivar now used as kale. Preference for tightly bunched leaves led to cabbage. Preference for eating immature buds led to broccoli and cauliflower.

And that’s only one species! If we step back and look at the entire genus (one level more broad than species), we also have turnip, rapeseed, radish, and horseradish.

Which is your favorite cultivar of Brassica oleracea?

Sources:

https://en.wikipedia.org/wiki/Brassicaceae

https://en.wikipedia.org/wiki/Brassica_oleracea