Wormy metaphors

A very felicitous eve,

Herr Doktor, and that's enough,

Though the brow in your palm may grieve

At the vernacular of light

(Omitting reefs of cloud) :

Empurpled garden grass;

The spruces' outstretched hands;

The twilight overfull

Of wormy metaphors.

Delightful Evening by Wallace Stevens (The Collected Poems. Vintage Books New York. 1990).

I like they way each line is interesting on its own in this poem and how it seems to be set against lazy adjectives. I'm not sure what 'Herr Doktor' refers too though? Given the time it was written (before 1936) it seems like it could be something to do with WWI maybe. I don't know. But the main focus seems to be on describing the night even if it is full of 'wormy metaphors'.