The poem is about the gap between designing nature and actually being part of it. The speaker is a landscape gardener, someone whose job is to arrange the outdoors so it looks natural, and the opening line admits a failure: "I cannot make natural." The sentence breaks off, as if the speaker can't even finish the thought.
The next lines flip the situation. "As if I rain" suggests the speaker wishing to become the weather itself rather than shape it from outside. Then the imagery turns strange and cold: a head "full of stepping thin / compasses of ice." You can picture thin, sharp points of ice, like the legs of drawing compasses, pacing across the mind. Compasses also measure and plan, which fits a gardener's work.
The mood is tense, brittle and a little uneasy. The speaker seems frustrated, maybe stuck inside careful calculation, longing for something looser and wilder. The poem doesn't explain itself, so it's best read as a feeling more than a story.