When I picked up a couple of inexpensive flat cars on eBay recently, I didn’t realize that one of 'em was something of a rarity:
http://www.postwarlionel.com/cgi-bin/postwar?ITEM=6826
Now, mind you, I think the trees I have on my 6826 look better than the bedraggled ones Lionel provided.
What do YOU think?
-MMM-
(and no, I don’t take scenery particularly seriously. Why do you ask?) 
The thomas troublesome trucks look good with tree loads.
As long you don’t have any bridges to go under, you are good. If you did, then would need the bedraggled ones.
I think your flatcar looks very nice.
The 6826 flatcar with Christmas trees is only scarce when it has the original Christmas tree load.
Reproduction loads are available.
Thanks!
Or, you can get these trees at Walleyworld for a buck a pop! A little duct tape trimmed to look like a tree bib and a small square of double sided mounting tape on the bases and away you go! 
Mitch