MArcomage

It makes sense. A natural wall that causes some opponents to become lost.

I wonder about it costing recruits to play it, though, since hedges are non-humanoid (or animalian, or particularly sentient).

Well they are alive though, rather than being made of clay or bricks or whatever, and they're not particularly mystical, so I think recruits is the best fit. Plus, it's kind of interesting to have more defensive greens, since there are so few.

I suppose the tower must employ a substantial crew of gardeners to maintain the thing.

I was thinking of the Dark Forest card which is just recruits.

Well, the dark forest is being filled with monsters of the night; the eyes you see in the brush at night. While the hedge doesn't really need food, men, armour, or weaponry (of which recruits tends to represent). I thought it would be a 2/2/2 card. The earth for it to grow in, the magic to make it grow, and the monsters to make sure those lost people stay lost. Edit: I just noticed my post partially contradicts itself, oh well, hope you get the point.