Thorny Ensnaring Strike

The target takes an extra 1d6 Piercing damage from the attack as grasping vines appear on it, and it must succeed on a Strength saving throw or have the Restrained condition until the spell ends. While Restrained, the target takes 1d6 Piercing damage at the start of each of its turns. At the end of each of its turns, the Restrained target repeats the save, ending the spell on itself on a success.

Using a Higher-Level Slot. Both of the damage dice increase by 1d6 for each spell slot level above 1.