Damn. i was going to ask do you water it? Untill i noticed your tag line it is tho.... 
This for TA? The default trees are located in,
C:\Your GC2 Installation Location\GalCiv2\Twilight\Data\English\TechTrees
To save your modded tree place it in,
C:\Your GC2 Installation Location\GalCiv2\Twilight\Mods\Data\TechTrees
Very similar paths for DL and DA.
I have only scratched around with the editor myself, editing the XML.s directly is my preffered method.
