You could say Grass starters and I don't have a long-standing history together. They always get the short straw and wind up stuck in the PC at some point.
Treecko was put away in Emerald immediately after it got to Sceptile.
Torterra in Diamond tried, but didn't prove itself effective enough to keep around.
Chikorita in SS never made it to Meganium (until White when I had nothing better to do)
And even when I pushed my Serperior to 50 in White 2, I boxed it.