If you carry a small section of groundsheet, most hammocks can easily be set up on the ground like a bivvy bag. Worth carrying a bit of extra guyline and pegs so you can use your bike, lamposts, a single tree, etc, to keep the head end of the hammock and tarp lifted off your face.
I've always wanted to get a hammock for touring, but never got past the 'what if there are no trees' aspect.