This moveskill can be used by Pokemon that have the ability Harvest or possibly Seed Sower or Ripen, or that know the moves Grassy Terrain, Leech Seed, or possibly Growth. When used, this moveskill will bonemeal all the grass blocks, crops, saplings, or other bonemealable stuff in a square of a certain size around the user. That size would be determined by the Pokemon's Special Attack. The larger the Special Attack, the greater amount of area that gets bonemealed. The max might be a 32x32 or 40x40 block side length. Alternatively or additionally, you could make a larger Special Attack cause more "bonemeal uses" on the blocks, so sapplings are more likely to grow and crops grow more stages.
I'm suggesting this because I feel we could use some new moveskills. Also, most moveskills that have the strength of their effects depend on the user's stats use the Attack stat, namely Cut, Dig, and Ground Birds with Smack Down as the base move. Only Ground Birds with Gravity as the base move uses the Special Attack at the moment, so physical attacking Pokemon are better moveskill users than special attacking Pokemon. "Grow Plants", on the other hand, definitely sounds like it would use Special Attack, so I feel it could help even things out.
If you are worried about this moveskill making Leaf Stone tools pointless, I'd say Leaf Stone tools are already rather pointless. The tools don't have great durability (same as Iron, which you can easily get from Steel-types) and it is often rather silly to waste rare and valuable Leaf Stones on a bonemeal tool, especially since you can usually just wait for stuff to grow or use actual bonemeal, which is easy to get as a lot of common Pokemon drop bones. There's nothing for the player to lose by using this moveskill though, especially if you make it long-range.