'Poplars' in the Bible

"On the first day, take branches from impressive fruit trees, branches from palm trees, boughs from thick trees, and poplars from the brooks. Then you are to rejoice in the presence of the LORD your God for seven days.

They offer sacrifices on the mountain tops, burning offerings on the hills, under oaks, poplars, and terebinth trees, since their shade is very good. Therefore your daughters are prostitutes and your daughters-in-law commit adultery.