If he had reached it, he would've recovered first and she wouldn't have been able to get what she needed. In fact, Ming Yue would've died if she let him reach the Evergreen Heart first.
As for the cut tree sapling, it quickly wilted away. The multicolored leaves and flowers from all of the other plants disintegrated. It turned to dust within seconds.
Cheng Wei wheezed, forcing himself to sit up. Roots came out of the ground, forming a little seat for him to rest against. Looking at her, there was a hopeless smile on his face, a look of defeat and ridicule towards himself.
"Perhaps it was impossible this entire time", he said, "I was reaching my own limit."
He suddenly chuckled for a bit, coughing by the end of it.
"The Eternal Heart was in such a delicate state, one wrong move could've ended things but I managed."