Entangling Blast
Hitting a creature with eldritch blast may grapple it with roots and vines.
Prerequisite: 5th level, eldritch blast cantrip, Old Wood patron
When you hit a creature with eldritch blast, the creature must succeed on a Dexterity saving throw or be grappled by roots, vines, and other vegetation until the end of its next turn. The DC for this saving throw and to escape this grapple is your spell save DC.
Source and licence
From Tome of Heroes.
Licence: Open Game Content (OGL 1.0a).