It seems that FSX uses a different model for trees in each season and these are located in the vegetation.bgl file.  On that basis I am not sure how you would be able to use them in a scenery placement tool and have their texture change by season.  I suspect this works if you use the autogen tool to add them but I am not experienced with that to say.

CAFedm wrote on Jun 27^th, 2008 at 4:11pm:


For my small projects I used either FSX_KML or SBuilderX to create
landclass polygons of the type of 'forest' I wanted. This uses the
autogen trees and they will change with the seasons.

Go over to the Avsim FSX Scenery Library and do a search on "Tokol".
That should take you to my scenery file I created to enhance the
rather bare default LHTL. Practically all the vegitation you see in
the thumbnails was added using landclass polys. I did add some
individual trees in a few spots early on until I discovered that they
didn't change with the season. I left them there anyhow but from
then on used the landclass approach. I was quite pleasaed with the
end results but it did take some experimentation

Here's a link to one of the thumbs...I'm 7000 miles from my home
machine ( actually only a few kilometers FROM Tokol at the moment )
otherwise I'd upload a sample here....

http://library.avsim.net/sendfile.php?Location=AVSIM&Proto=file&ImageID=192515

    Paul