Despite the fact that our poet is very much a man, our speaker is very much a woman, and a widow at that. Although we don't know much about her specifically, we can totally picture the scene: a lonely woman stands at her window. She's looking out at the grass, the trees covered in flowers, but not feeling like she's a part of that growth and brightness.
She's simply too busy grieving for her dead husband. In fact, for the most part, it seems that our speaker is a widow and nothing more. The loss of her husband has consumed her life, and all the little pleasures it once held for her. She is defined by his death, and his death dictates how she sees the world around her.
We also notice that, despite her great sadness, she has a sense of control. She's not screaming and crying. She's not down on her knees praying for her husband to return. Her grief isn't loud or messy. No, it's a cold weight that "closes round" her. She speaks plainly, uses as few words as possible, and doesn't ask for much from us readers. She doesn't make any effort to sound deep. We don't pity her. But we do worry for her. After all, that last image doesn't sound too promising.