They look great outside!
I like to keep my outdoor pens HEAVILY planted. The only dirt area is around the perimeter and it's there from pacing along the walls. I also like to lets patches of the weeds grow really tall so they can burrow into the humid area at the base. I think it helps them stay smooth
I'm hoping the grass takes off with frequent watering. The dirt/peat mix in the one side is on top of the grass because the area was incredibly uneven from pulling rocks out. I'm hoping the grass comes up through. Or weeds, is be happy with anything green lol.
I'm going to go get some grapevines as Tom suggested and we have already moved the mandevilla.
Elohi(Earth)