It definitely wouldn't be the left image. With legs like those, you could never pull the pants up past the first (or I guess technically last) level of branching. It would either be the big pants or a large number of seperate, smaller pants on each of the lowest branches.
If the pants are stretchy they could fit one of the lowest (already pantsd) branches in each leg of the jeans, and easily pull it up. You need bigger and stretchier pants as you go up the tree, though.
The max size of required pants stretch will be the standard size for the right picture, since each leg already wraps half of the tree. That confirms viability at least, so now I think it's down to comfort, and does the stretch retract in a restful position, or does stay all loose and cumbersome?
The first one is clearly wrong because no-one (oh alright, almost no-one, Toe-Jeans Georg) wears leg-wear on our toes.
Third option: The top layers are covered by a poncho and only the eight pairs at the bottom have leg-wear. This works when considering each subtree as a separate tree in its own right, up to arguing about how many ponchos are then required.
Fourth option: The top two branches wear leg-wear and those below go in footwear of some sort.