All day I have watched the purple vine leaves
Fall into the water.
And now in the moonlight they still fall,
But each leaf is fringed with silver.
Amy Lowell, as I've mentioned before, is an Imagist poet. Imagist poetry depicts in a way what is, without moralizing or trying to draw any sort of conclusion. Some find it wanting; I find it refresing and enjoyable. For me, Imagist poetry creates a scene in which one may mentally walk around. The picture Lowell gives is just concrete enough to picture, yet not so concrete as to disengage the reader's imagination.
What's a better picture of autumn than a falling leaf in day and by moonlight? Much as the poem's narrator spent all day watching the leaves fall, we, the reader, picture in our minds the leaf falling, limned by a sunset, by a glorious moonrise, by the stars off the water, gently touching and rippling that water's surface. It takes us to that place without telling us how we should feel. Is it sad? Is it peaceful? Happy? That's not for Lowell to say. She presents the scene for us to explore in our mind's eye. I like that a lot. This poem, for me, is a nice place to be. Serene. I hope you take your time to walk around this poem's landscape in your mind.