You pass through Route 1 on your way to the Pokémon Research Lab.
Go north and you will find a row of sleeping Wooloos blocking the way. Go east into the tall grass. You now have five pokéballs, so feel free to catch some pokémon as you go. Just press X during the battle to choose a pokéball and throw it. Try to reduce the wild pokémon's HP before you throw the pokéball to make it more likely that you will catch it.
You can move slowly to avoid the pokémon that you can see in the tall grass, or you can push the left control stick like a button to whistle and get the attention of the pokémon that you can see. If you move quickly in the tall grass, you might make a patch of grass start to rustle, and if you walk into the rustling grass, you will have a wild pokémon encounter.
The pokémon that you may see in this area are Nickit, Rookidee, Skwovet, and Wooloo. The pokémon that can be found in rustling patches of grass are Blipbug, Caterpie, Grubbin, Hoothoot, and Skwovet.
After the first patch of grass, you will find a Potion.
Farther along the path, you find 2 Paralyze Heals.
After you get past all the grass, go north to reach Wedgehurst.