Garden of Eatin' / Vegetables

There’s a Fibonacci Fractal in This Remarkable Romanesco Broccoli

Romanesco broccoli florets

Few things in the garden are more mesmerizing than the Italian heirloom plant known as Romanesco broccoli.

The chartreuse bud looks like it was sculpted by a fine artist with its distinctive spiraled pinnacles. It’s an edible flower (just like heads of broccoli or heads of artichoke) that we eat as a vegetable.

Romanesco belongs to the genus Brassica, which is unusual in that instead of individual species, it bundles all of its members (such as broccoli, cauliflower, Brussels sprouts, cabbage, kale, mustard greens, kohlrabi, and turnips) into one species, making them all Brassica oleracea.

(If you remember high school science, plant taxonomy goes like this: kingdom, order, family, genus, species, and sometimes, subspecies.)

That means Romanesco broccoli (which is sometimes called Romanesco cauliflower) is neither a broccoli nor a cauliflower, though it’s often grouped botanically with cauliflower (Brassica oleracea var. botrytis).

It is its own cultivar and by the looks of it, this head-turning vegetable is truly in a class of its own.

Close-up of a Fibonacci sequence spiral on Romanesco broccoli

The history of Romanesco broccoli

Romanesco tastes like a nuttier and crunchier version of cauliflower, and in my opinion, is more flavorful than either broccoli or cauliflower.

It dates back to the 15th or 16th century, where it was thought to originate in the Lazio region of Italy. (Rome, from which the plant gets its name, is the capital of Lazio.)

Called broccolo romanesco or cavolo romanesco by the Italians, it was grown in the countryside and didn’t make its way to the United States until the 20th century.

Botanists believe that Romanesco broccoli was developed through cross-breeding, and its naturally occurring pattern was reinforced by human selection over centuries. The cultivar is both an heirloom and a hybrid, depending on the specific seed you have.

Read more: The Stories Behind Heirloom Seeds

Several varieties of Romanesco broccoli exist, and some farmers have crossed open-seeded varieties with each other to produce hybrids that are faster growing.

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Baker Creek Heirloom Seeds and Botanical Interests both carry an open-pollinated heirloom variety, and a few seed catalogs carry F-1 hybrids like “Veronica” Romanesco brooccoli.

Recommended reading: Decoding Your Garden Seed Catalogs

Romanesco is typically found in better supermarkets, health food markets, and farmers’ markets from spring through early fall. If you can’t source it locally, you can try an online natural food co-op like Azure Standard, which carries organic Romanesco broccoli all summer.

The plant is grown and cooked like your run-of-the-mill broccoli, but its pointy fractals are too pretty to puree or dice into little chunks.

I love to roast or grill the heads whole and drizzle them with sauce (my favorites include a creamy feta dressing, balsamic vinaigrette, and carrot top salsa), and for special occasions I make the Roasted Romanesco and Broccolini Salad With Wilted Arugula from The No-Waste Vegetable Cookbook.

A steaming head of Romanesco broccoli out of the oven

How to find the Fibonacci fractal in Romanesco broccoli

Romanesco broccoli is an intricate work of art and a mathematical marvel. Did you know it’s a beautiful example of a Fibonacci fractal in the natural world?

Last year I picked my Romanesco a few days too late, and its famous spiral had already started to unravel, resembling an average cauliflower.

But this year, I remembered to harvest it earlier (and thankfully, it weighed much less than the 25-pound Broczilla that I grew many years back).

The part of the broccoli that we typically eat — what we call the head — is actually the flower bud of the plant (although broccoli leaves are just as edible and delicious, and can be cooked like any other green).

Worth a read: 11 Vegetables You Grow That You Didn’t Know You Could Eat

The tight clusters that form the head are called florets (or small flowers).

Romanesco broccoli fractals

On a Romanesco, the whole head is made up of smaller heads that mimic the shape of the larger head, and each of those smaller heads is made up of even smaller, similar heads. It keeps going, and going, and going…

You’re looking at a natural fractal — quite simply, a detailed pattern that repeats itself ad infinitum. (But since a head of broccoli can’t go on forever, math purists would call this an approximate fractal, since it has a termination point.)

If you break off a floret, it looks like a mini broccoli with its own mini florets.

Fractals are fascinating in that way; no matter which part of the fractal you zoom in on, it will be an identical version of the bigger picture.

Romanesco cauliflower florets
A head of Romanesco broccoli

If you ever have the chance to study a tight head of Romanesco up close, you’ll see a spiral emanating from the center point, along which all the smaller florets are arranged.

This is the Fibonacci spiral, a series of arcs whose radii follow the Fibonacci sequence.

You remember the Fibonacci sequence from school? Where each number equals the sum of the previous two numbers: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, and so on.

If you count the number of spirals in one direction, and then count the number of spirals in the other direction, they will be — without fail — consecutive Fibonacci numbers. Every time.

Intrigued? Confused yet? I know I was. I’ll let this math geek explain it better with a visual.

If you don’t have a head of Romanesco to test out this mathematical wonder, try it with other self-similar forms from your garden. The spiral patterns in sunflowers, pinecones, and pineapples are all examples of Fibonacci sequences in nature.

Fibonacci spirals on a sunflower

Isn’t it amazing how something so precise like a math formula can occur in something so organic like a head of broccoli?

Fibonacci fractals found on a head of Romanesco cauliflower

This post updated from an article that originally appeared on April 25, 2012.

Linda Ly About Author

I'm a plant lover, passionate road-tripper, and cookbook author whose expert advice and bestselling books have been featured in TIME, Outside, HGTV, and Food & Wine. The No-Waste Vegetable Cookbook is my latest book. Garden Betty is where I write about modern homesteading, farm-to-table cooking, and outdoor adventuring — all that encompass a life well-lived outdoors. After all, the secret to a good life is... Read more »