Monday, December 12, 2011

Helicopter Leaves

Ok, I admit it, I'm from the desert.  I can name you the type of cacti and the latitudes and altitudes where each one grows (maybe that's another lesson).  However, trees are definitely not my specialty (to give you an example: my thermo prof in undergrad was surprised that I didn't know what an acorn on the ground was, but to my defense it didn't have the cap on it as the cartoons, or in particular Ice Age, depicts since the cap fell off in the drop from the tree).

Anyways, we've been having an extremely long fall (or so it seems).  Leaves are still falling from our trees around here and offer at least a few minutes of science-y fun.  Being from Oregon, John knows much more about trees than I do.  He had pointed out the helicopter leaves to me once in undergrad at UP.  However, I had no idea that we lived next to a tree for almost four years that dropped helicopter seeds until John pointed it out to J recently.

For background purposes: helicopter leaves/whirlybirds are seeded pods (the linked article says they are from S. American Tipu Trees) that are shaped in such a way that they spin on their way down.  My quick Google search is popping up Maple trees give off helicopter leaves too.  That seems a little more common.  Maybe you have them close by!

We've been dropping them off of our balcony lately (as seen by the seeded mess on the pavement below).

Why do the helicopter leaves spin?
Their special shape slows their fall down.  The seeds are shaped like a helicopter blades, catching the air as they fall.  According to a Science article, this allows them to travel longer distances if caught in the wind.

Try at home:
Drop different leaves from a height - note their shapes and how they fall.
Drop a different object (ie a soft ball) from the same height.  How does it fall compared to the leaves?


  1. Yup. Maples indeed. Some give them in spring, some in fall. Tons of fun with kids

    A special challenge can be had by attempting to throw them up in the air to gain a little extra altitude before beginning the fall back to earth. Techniques for this vary and it's really hard to get them more than a few inches above one's own hands-that drag component has been very, very well designed by nature!

    Also, one can plant those seeds (of course). My 4-year old daughter planted one in the spring and very proudly cared for her baby maple tree all summer. (It met an unfortunate end when it fell off the porch railing, behind a bush and got forgotten about in September, but four months of caregiving was pretty impressive from the little one).

  2. Great ideas! I resorted to videoing them off of the balcony since throwing them is difficult, but way fun! We typically just end up throwing them as high as we can (a few inches above our heads).

    Thanks for reading and the comment! I'll check out your blog too. I <3 math.