25d39a0e_der_com___Revit_3D__March_2008__In_Revit_2009___
[Revit 2008 Feature] Seasonal settings [For more information] Specifying a Render Appearance for an RPC Family [In Revit 2009...] 
For many plants, you can now select a render appearance that shows a standard version of the plant or a fall version of the plant. You specify this in the plant family. The plant season is no longer a render setting.
BIMBuilder.com / Revit 3D: March 2008
In Revit 2009...