Some of them had recently built a pulp mill, and he called my attention to the young growths of "popple" we could see from the car window and remarked: "There's good pulp material in those trees, but it's not easy to get 'em cut. You'll strike lots of Catholic lumber-jacks who won't have anything to do with cutting a popple tree, and they won't cross a bridge or sleep in a house that has popple wood in it. There's a tradition that the cross on which Christ was crucified was of popple, and they say the wood was cursed on that account.
Source: wiktionary