Maple seeds are amazing things. Because they rain down on my garden in their hundreds every spring, I have become something of an expert in their myriad tricks. First, there is the flying thing, that carries them up to 50 yards from the tree. ("Hebicopters," one of my toddlers called them, and thus they shall always be for me.)
But that wing has not finished its job when the seed hits the ground. It helps the seeds gather into clumps, like this one. Within these clumps, the seeds jostle around until some of them have their seed heads pointed to the ground and their wings up in the air.
When the wind blows, the wing vibrates, and this motion drives the seed down into the ground. It was seeing upright seeds vibrating in the breeze that made me realize that the seeds did not just lie passively on the ground.
I have seen seeds an inch an a half long (3 cm) disappear into the ground in just two days. As a result of this self-burying technology, the germination rate of these seeds is astonishing when they fall on disturbed ground. One year I decided not to try to pick up any seeds out of the garden, thinking that only some would sprout, and it would be easier to pull up a smaller number of seedlings than collect a large number of seeds. Wrong. The germination rate must be less than 100 percent, but it is close enough to create a solid lawn of tiny maples. So now I pick up all the seeds I can find.