Oh, man, awesome. You would've found these installations at [redacted] last week.
If I taught science, I'd toss this photo on the wall during one particular unit and let 'em fight over the method. Any readers know how this thing happened? I'll toss the answer into the comments if y'all founder too long.
[Hint: the answer does not involve a really really tiny lawnmower.]
BTW: a month into summer and I'm totally off my game. Lemme just say that these lawns sculptures involve photosynthesis in kind of a crucial way.