A creature that you can see within range makes a Constitution saving throw, taking 8d8 Necrotic damage on a failed save or half as much damage on a successful one. A Plant creature automatically fails the save.
Alternatively, target a nonmagical plant that isn't a creature, such as a tree or shrub. It doesn't make a save; it simply withers and dies.
At Higher Levels
The damage increases by 1d8 for each spell slot level above 4.