Verdure means green growing things taken all together — grass, leaves, moss, young plants — and also the fresh green look they give a place. Where verdant is the adjective, verdure is the stuff itself: "the verdure of the valley" is everything green in it. It is an uncountable noun, so it takes some, much, the, but never a. This is a distinctly literary and old-fashioned word. You find it in nineteenth-century novels, in poems, in careful nature writing and in descriptions of gardens and tapestries. In ordinary modern English people say greenery, or just the plants, or how green everything is. So verdure is a choice you make for tone — it slows a sentence down and makes it sound formal and a little romantic. It can also carry a sense of freshness and youth in the plants, not just colour; withered leaves are green-ish but they are not verdure.

（文言、書面用語）綠意、青翠的草木；一片綠