What technique did the writer used while composing "Loveliest of Trees"?

Much of the techniques Houseman uses in the poem concerns his playing with imagery.  The opening stanza depicts a tree in full bloom with language that illuminates this such as,  "the cherry" hung in bloom along "the bough," and the look of the tree in comparison to "Eastertide."  In the second stanza, the poet uses the metaphor of human age to reflect the potential change in the tree.  In applying age and its effects to the life of the speaker, the reader can only envision what is going to transpire with the tree.  Rather than create the image of winter being one of decay, the last stanza brings to light that the beauty represented by the tree can be brought out when  it is "hung with snow."  This picture helps us construct a vision of the tree where its beauty is present in both winter and spring.  Such a vision of snow is not one of decay, but another element that highlights the beauty of the tree, and allows the speaker another opportunity to revel in its loveliness.