Monday, May 4, 2009

How far can a Dandelion Spore Travel?

When I arrived home from work, my son was raiding the dandelions in the back yard. He was doing what we all did at six: blowing the spores off and making a wish when he cleared the stem. Of course I joined him. After watching the spores float around the yard, he asked me how far can one of them go.

Happily, the intertubes were not too clogged that evening and I managed to find a few research articles on this very subject (yay, Google Scholar!). I have the sneaking suspicion that the scientists who do this work are just looking for excuses to lay on the grass making wishes with their children. Here's a likely manuscript title (Tackenberg et al): "Dandelion Seed Dispersal: The Horizontal Wind Speed Does Not Matter for Long-Distance Dispersal - it is Updraft!" The conclusion in this paper is that for a dandelion seed to go 100 meters or more (long distance by their definition), updraft is the dominant factor. In slight contrast, some (PDF, Stephenson et al.) other (Greene) authors report that the wind speed required to remove similar seeds from the stalk is an important factor. The Stephenson article also considers 100 meters to be a long distance for seeds to travel, so while I suspect that some 4- or 5-sigma seeds can travel into the upper troposphere and thus very long distances it seems that most seeds of this type only travel 100 meters or so.

I had expected that the seeds would make it further than that.

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