Images and groves - Images of different idols, and places for the abominable rites of Ashtaroth or Venus.

And they set them up images and groves in every high hill, and under every green tree. That is, statues and idols; for groves of trees could not be set under green trees; but they placed idols of stone, and of wood, as the latter were, in such places as Heathens were wont to do; see Jeremiah 3:6; see Gill on 1-Kings 14:23, so the Indians to this day have idols dispersed here and there in the fields, placed in little groves, or at the foot of some hill that casts a shadow (h).
(h) Agreement of Customs between the East Indians and Jews, art. 5. p. 34.

They set up for themselves monuments and asherim on every high hill, etc., - a practice condemned in 1-Kings 14:16, 1-Kings 14:23, as early as the time of Jeroboam. In this description of their idolatry, the historian, however, had in his mind not only the ten tribes, but also Judah, as is evident from 2-Kings 17:13, "Jehovah testified against Israel and Judah through His prophets," and also from 2-Kings 17:19.