“The Ballad of the Harp-Weaver,” by Edna St. Vincent Millay is one you might consider. It’s a little old fashioned, but hey so is Frost and Keats. Oldies but goodies:D
The Canadian poet Archibald Lampman writes about nature and the seasons frequently. His poem "Winter" was set to music by Loreena McKennitt. His most famous collection is "Among the Millet and Other Poems." Lampman's descriptive language and imagery make him one of the finest North American nature poets.
Lesser known than Lampman but still an exc ellent nature poet is the "Peasant Bard" Josiah Canning. He wrote an entire series of poems dedicated to the twelve months of the year, as well as many other poems about country living. Canning lived most of his life in Western Masschusetts.
A short poem that has a traditional theme about the transitory nature of the seasons and life is Carl Sandburg's (1918) "Autumn Movement":
I cried over beautiful things knowing no beautiful thing lasts
The field of cornflower yellow is a scarf at the neck of the copper sunburned woman, the mother of the year, the taker of seeds.
The northwest winds comes and the scarf is torn full of holes, new beautiful things come in the first spit of snow on the northwest wind, and the old ones go, not one lasts.
In this poem, also, is the concept of the regeneration of Nature as the same northwest wind destroys the old crops while at the same time bringing in the "new beautiful things."
Another one to examine would be Keats' Ode to a Nightingale, in which the natural world represents one of eternity and unity, compared to the fragmented and singularly mortal life of human beings. His description of the natural world in lush imagery is fairly compelling and powerful. Similar to Shelley, Keats uses a natural experience and love of nature to reflect a personal experience.
"In the Spring and in the Fall" by Edna St. Vincent Millay is a good one for you to consider. She uses the two seasons to parallel the beginning followed by the end of a romantic relationship. Love grows in the spring when it is new, and it fades in the fall. Since springtime is associated with life and growth and since fall is associated with the end of the life and growth cycle, her poem addresses both seasons in a traditional way. It's a lovely poem, although a sad one.
Robert Frost's Walking by woods on a snowy evening, if you want a short poem or The Road not taken is for autumn