Anything that looks like grass can be punched ... either brown or yellow, short or tall. All seem to have the same chance of dropping something.
Remember tall grass is the one block variety, not the double-tall grass.
The Quest Book sapling quest says "Long Grass", not "Tall Grass". I don't know what "Long Grass" is, but it isn't the "Tall Dead Grass" because the Mutandis doesn't do anything when I click on that grass.