The tulips are too excitable, it is winter here. (1)
This isn't really a "nature poem" in the typical sense, but based on the first line, you might think it was. In this opening moment, there's no way to tell that we aren't outside, except for this: tulips don't grow in wintertime. So something's off here.
They pass the way gulls pass inland in their white caps (12)
Check out how the speaker sees something natural (seagulls) in a very unnatural, human space (the hospital). Why do you think she chooses this particular image to describe the nurses?
My body is a pebble to them, they tend it as water (15)
On the one hand, this is just a metaphorical way of expressing the way the nurses treat her. But on the other hand, it's yet another way that the natural world creeps into almost every line of this poem. Once you start looking, you start to see the natural world just about everywhere.