Lawns and Open Ground
Open ground is the hardest thing to light, because there is nothing for the light to land on. A beam across a lawn does nothing at all until it hits something.
So the answer is almost always vertical: posts. A run of green oak, galvanised or Corten posts carrying festoon across an open space gives you a lit ceiling and a defined edge where there was none, and it works from the house as well as from within it.
If you must put fittings in the grass itself, use in-ground walkover units flush with the surface — a spike in a lawn is something to mow over exactly once.