One of the few crowd control spells not subject to creature type restrictions (humanoid, beast, demon, etc.). It is, however, unreliable. Any creature that is immune to nature spells, as is common among elementals, is immune to Entangling Roots.
/Patch 3.0.2 (14-Oct-2008): Entangling roots is now usable indoors.
/Patch 2.0.1 (05-Dec-2006): All crowd control effects have a chance each second to break earlier, and their duration is capped at 12 seconds in PvP. The chance increases with resistances and the level difference between the target and the caster.
Patch 1.7.0 (13-Sep-2005): Entangling Roots now shares the same duration in pvp as other long-duration forms of crowd control (ie: polymorph, fear, sap).
Patch 1.4.0 (2005-05-05): Now subject to diminishing returns in PvP. This is considered an immobilizing effect.
Patch 1.2.0 (18-Dec-2004): Entangling Roots: Rank 4 moved to level 38.