 Cardboard, if you want to do that. The shredded mulch is going on top. And then I haven't mentioned, I should have, that you manage the weeds after doing all that stuff properly. You manage the weeds as they come up young, which they're going to do here and there. They don't know how thorough you were and whether you used corn gluten meal as the natural pre-emergent. You spray the emerging stuff.