He's staring down one road, trying to see where it goes. But he can only see up to the first bend, where the undergrowth, the small plants and greenery of the woods, blocks his view.
This is where we start to think about the metaphorical meanings of this poem. If our speaker is, as we suspect, at a fork in the road of his life, and not at an actual road, he could be trying to peer into his future as far as he can. But, since he can't really predict the future, he can only see part of the path. Who knows what surprises it could hold?