Helicopters, maple ‘copters, whirlybirds, twisters or whirligigs – no matter what you call a maple seed, they’re still an endless source of fascination. Many of our Farmers’ Almanac readers and Facebook fans have been asking about the large number of “helicopters” they’ve been seeing, and does it mean anything?
First, the technical term for this winged seed is samara, which refers to a specialized fruit that is designed to travel long distances from the parent tree. Some ash and elm trees also produce samaras, although the maple’s samaras are the very best at flying.
Maple trees that are healthy sometimes skip a year in seed formation, either due to poor pollination or to an exceptionally good growing season the year before. An over-abundance of samaras sometimes means the tree experienced some sort of “stress” the previous year, so producing a bumper crop of seeds is the tree’s way of carrying on the species, should that stress continue and that particular tree not survive.
So why do maple seeds fly? One reason is that among trees, maples have some of the largest, widest canopies. That means for a seedling to grow, the seed can’t simply fall to the ground beneath the tree like a nut or a fruit. And, since only a few animals eat the seeds – mostly turkeys, finches and on rare occasions, squirrels and chipmunks – there is very little chance that wildlife will pick up the seeds and carry them elsewhere. To get around these obstacles, maples developed winged samaras as a way to transport their fruit to sunnier, more hospitable places.
A natural lesson in aerodynamics
Maple seeds are one of those natural wonders that feature a nearly perfect design. In fact, scientists are using what they’re learning from these flying seeds to develop micro flying machines and even tiny helicopters that can be used for space exploration or to learn more about the atmospheres of planets like Mars.
It all starts with the shape. With a long wing that balances the weight of the seed, maple seeds are perfectly designed for flight. Since the seeds don’t fall away from the tree until they’re dry, they’re very light, which helps them travel farther.
If you examine a maple seed closely, you’ll notice that the wing gets wider further away from the seed. When the seed spins, the air moving over the wide end of the wing moves faster than the air closer to the seed, which gives the seed the lift it needs to stay aloft. Then there are the veins on the leading edge of the wing, which generate just enough turbulence to help it cut through the air.
Those are the basic ideas behind flying maple seeds, but when scientists dug a little deeper into the aerodynamics, they found something interesting. While observing the seeds in a smoke-filled wind tunnel, researchers noticed that they actually form a small vortex – like a tiny tornado – atop the wings. That vortex lowers the pressure above the seed, generating even more lift. Insects and hummingbirds rely on the same kind of vortex to hover in one spot.
Wings aren’t just for flight
The wings give maple seeds another huge advantage. Once a maple seed lands, the wing helps it stand upright between blades of grass or other foliage. The upright seeds have a better chance of embedding themselves into the soil below. Once pressed into the soil – whether by a passing foot, the weight of snow or something else – the wings break away so that the seed can germinate more easily.
Now that you know more about the maple’s flying seeds, you’ll be even more fascinated by the hundreds of them you see swirling towards the ground each year.