Does not matter if you are ondeed, offdeed, have permissions, are in a house, or have it loaded into a vehicle... there is no option at all to bash/destroy large planters. I was, at the huge detriment to my armor and wagon, able to drive onto a lava tile and unload one. This is by no means viable, I nearly died.
Edit: They also don't follow color for wood type, Birchwood and Firwood look the same, is this a bug or intended?