Read "Lichens" at The Eldritch Dark:
This poem from Clark Ashton Smith (CAS) really plays to the author's strengths, combining a close observation of nature with invocations of the weird and the fantastic:
Old too they seem and with the stones coeval—
Fraught with the stillness and the mystery
Of time not known to man;
Like runes and pentacles of a primeval
That none may use nor scan.
CAS' ability to see the inherent magic in the lowly (and easily-ignored) lichens speaks to both his sensitivity to the natural world and his ability to express what is prompted by that sensitivity. Great stuff all around!