There is a word to describe the first growth of spring, rare in a way as having grown within the English/French languages without roots from either Greek or Latin, wholly suitable to a forest people. The first growth of spring so impressive it has words of its own: burgeon.
Both as a noun, burgeon the bud itself, and a verb; to burgeon, as in to burst forth. Burgeoning: the process of the act itself.
burgeon/burgeoning definitions from the Compact Oxford English Dictionary, Oxford University Press, 1971