You know, thinking about it... I actually never really did use a Grass-type Pokemon in Sinnoh. I usually opted for Electric and Water-types when it came to dealing with Water and Rock or Ground-typed Pokemon.
It's funny, because in other Generations, I would end up using a Grass-type Pokemon, such as Vileplume or Victreebel in Gen. I, Bellossom in Gen. II, Sceptile or Breloom in Gen. III and Serperior, Leavanny or Lilligant (to name a few) in Gen. V. It wasn't really anything I thought about before, but now that I have, I'm surprised Generation IV is the only Generation that I've not used a Grass-type Pokemon.
Except for in my HG/SS run, but that doesn't really count. xD