ALEX CHADWICK, host: OK.  One more intriguing footnote to this story:  a note that Lewis Libby      sent to Judith Miller upon her release from prison.  Quote, "You went      into jail in the summer," he wrote.  "It is fall now.  Out West where you      vacation, the aspens will already be turning.  They turn in clusters      because their roots connect them.  Come back to work and life," end of      quote.</s>ALEX CHADWICK, host: Some have taken that as an attempt to send Judy Miller a message,      although exactly what that message is who knows.  The letter piqued the      interest of the Explainer team at the online magazine Slate.  Here is      Slate's Andy Bowers to answer the question:  Do the leaves of aspen trees      really turn in clusters because their roots connect them?</s>ANDY BOWERS reporting: No, they don't.  Aspen trees do grow in clusters, or clones, that share a      common root system, and they do have identical DNA.  That doesn't mean,      however, that they all turn--that is, change colors--at the same time.      Leaves turn colors in the fall according to both genetic and      environmental factors. The exact day depends on the sunlight, temperature      and precipitation to which they've been exposed.  Aspen clusters can be      huge, with the largest recorded spread out over 17 acres.  So certain      trees could get more sunlight than others and change color on different      schedules.  A week or more might elapse between the turning of the first      and last trees in a stand of aspen.</s>ANDY BOWERS reporting: However, shared genes do mean that when clusters of aspens turn in the      fall, they all turn the same color.  The leaves on every tree in one      clone may turn gold while those on trees in another clone turn crimson.</s>ALEX CHADWICK, host: Thank you, Andy Bowers, Slate senior editor.  That Explainer      was compiled by Daniel Engber.
Fall has arrived and the aspens are turning color, just as Dick Cheney's Chief of Staff I. Lewis "Scooter" Libby promised New York Times reporter Judith Miller they would. Slate senior editor Andy Bowers offers an explainer of the tree made famous by recent political intrigue.