Nearly two years after I started this thread, I can say I built a 12x12 pergola and I anchored it in planters and after a number of huge storms and high wind, the pergola hasn't budged.
I built 4 large planters and then I got 4 column forms from Home Depot and set the pergola uprights in them and filled up the forms with concrete.
Then, after the concrete had set, we anchored the uprights through the planters as well (as kudzu9 suggested) and then filled all the planters with dirt.
We had some super thick pavers (I think each paver was about 4 inches thick, the landscaping place said a dump truck could drive over them without issue), so I'm very confident in my decision to not anchor them into the ground.
Q
ravenwood
Q