The history of Barrenwort, why it got a B in Math, and how your garden is like a Gentleman’s club.

A flower is a surprisingly naughty thing. It is, inescapably, the part of a plant that makes more plants. That sounds benign enough, but to put it more euphemistically, a flower is the plant’s ‘nethers’, its ‘downtown’, ‘privy council’, or ‘pulpit’, 'Mrs. Fubb’s parlor’, ‘cupid’s corner’, ’Harbor of Hope’, or as they say, ’nature’s treasury’. In case I’m not being clear, a flower is a plant’s bathing suit area. If the people of Utah were plants, they would ban lectures on flowers and remove books with pictures of them from libraries. If Californian’s were plants, they would replace their flowers with different flowers and profess they were some other genus entirely.

In other words, your flower garden is the red light district in the world of vegetation. This makes pollinators the proverbial Johns, in a way, and it’s the flower’s job to maximize the fruits of their interaction. Much like in humans, various strategies are employed to meet these demands. The sunflower, for example, exploits a space saving mathematical algorithm in its seed arrangement called the ‘golden spiral.’ It is a remarkably efficient system, allowing the center of the seed head to continually add new seeds as the old grow larger, as if the manager of a brothel hired a calculus teacher to design an on-site nursery and early learning center. The plan utilizes the famous Fibonacci series and fittingly, Leonardo Fibonacci came about his sequence while contemplating reproduction (specifically in rabbits). You can read more about Leo and his rabbits here if you like. Each number in the numerical progression is a sum of the two numbers that precede it and it plays out as such: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, and continues to infinity.

*The Golden Spiral arrangement of sunflower seeds.*
*(Courtesy of Mathnasium)*

This mathematical relationship is seen throughout the natural world, from hurricanes to galaxies, and in plants it ensures optimal efficiency, maximum exposure to sunlight, and ideal utilization of the available space. Thus we have Fibonacci’s numbers showing up in the petal (and leaf and seed) arrangement of many of our garden favorites:

3 Petals: lily, iris
5 Petals: buttercup, wild rose, larkspur, columbine
8 Petals: delphiniums
13 Petals: ragwort, corn marigold, cineraria
21 Petals: aster, black-eyed susan, chicory
34 Petals: plantain, pytethrum
55, 89 Petals: michelmas daisies, the asteraceae family

Cat Haglund (for the Montana Natural History Center) beautifully explains why this is the case:

“Plants can't arrange their parts the way we'd pack a box of fruit, starting at one corner and working in rows, left to right. They grow outward from a central point, a tiny cluster of cells at the tip of each growing shoot called the meristem. To complicate matters, the meristem can't expand in all directions at once. Instead it produces new cells one at a time in a spiral pattern. The new cells grow radially away from the meristem as the meristem grows upward.

Think of the thread on a screw and imagine tracing the thread from tip to head, with leaves or petals appearing at equal intervals along the path. But only certain intervals will produce a viable plant.

If a stem put out petals at a rate of one per turn of the screw, all the petals would be lined up on the same side of the flower! The relationship between the number of petals or leaves per turn is often the ratio of two successive Fibonacci numbers. For Instance, a willow tree has three leaves for every eight turns.”

Fibonacci sequence in hurricanes and galaxies — *Fibonacci sequence in galaxies and hurricanes*

Wether employed for flower, grain, or structure, it’s a space saving, design forward system that would make the most Scandinavian of architects swell with admiration. But not all flora embrace this model, however. Epimedium versicolor, seen here, shirks the prevailing stratagem of optimizing the product of reproduction and instead advocates streamlining the frequency. Like fish net stockings or a tattoo just above the waistline, the flowers of the Epimedium are designed to send a clear message to would be pollinators. They are exotic and alluring. They eschew convention with their very non-Fibonacci-esque 4 petal bloom. According to Gerald Klingaman of the University of Arkansas, “They look like they were designed by a committee of Chinese artists intending to create something fantastic, yet still beautiful and delicate. The four long, narrow spurs radiate outwards and are about an inch and a half across. The center of the flower protrudes outward forming an almost square opening through which pollinating insects reach the working of the flower.” Much like cruciferous vegetables, named for their cross forming 4 petal flowers, the X marks the spot and is believed to behave like a beacon to airborne bugs, guiding them to a safe harbor of pollen rich treasure. Leaf cutter bees are apparently a particularly important pollinator of Epimedium.

Four petal cruciform pattern of *Epimedium rubrum*

The name Epimedium is a Latinized version of a Greek name for the unidentifiable plant epimedion mentioned in Pliny the Elder’s Natural History. Common nicknames include bishop's hat, fairy wings, and as proof that the universe has a sense of irony, both barrenwort and horny goat weed. Barrenwort because of a belief that the roots promote female sterility and Horny Goat Weed once famers took note of the stimulating effect it had on their livestock. Indeed, the species contains icariin, a weak PDE5 inhibitor, the same receptor leveraged in Viagra, Levitra and Cialis. Extract of Epimedium grandiflorum is commonly sold as a dietary supplement for similar reasons.

As a group, the Epimediums are herbaceous rhizomatous perennials in the barberry family. Most species are native to China but there are some that are native to the Mediterranean. They are rugged and tough and once established can grow in many locations where other plants struggle to survive. They generally prefer moist, lightly forested areas, but deep shade and dry soil rarely cause problems. Their flowers tend to bloom in late spring, between May and June, and although considerably more subtle, their leaves are heart-shaped, graceful, and charming. Despite taking a less computational route to phylogenetic success, Epimediums are enviable survivors. As Allan Armitage, professor of horticulture at the University of Georgia, so nicely put it, Epimedium is “a genus whose time has come, with plenty of attributes and very few faults.”