This poem is called "Grass," and hey—whaddaya know—it's spoken by the grass too. Our grass has got a distinctive voice and a pretty hardcore work ethic, so we're gonna go ahead and suggest that the grass is personified in this poem (i.e., given the attributes of a human being).
But this being said, the grass is most definitely not a human. It has a voice and it has a drive to work, but it doesn't have feelings, emotions, or memories. In fact, part of what makes this poem so interesting is the gap of perspective that exists between us (the poem's readers) and the grass. The fact that the grass is so casual, so whatever, about the work that it's doing (like covering bloody battlefields and effectively erasing history) makes us realize that we are the ones who are going to have to step in and do the work that the grass doesn't do. Our speaker may be personified, but that doesn't mean that the grass is humanized. For that, we're gonna need some… humans.