So I think this was the new record for the longest thing strapped to the bakfiets so far. The Christmas tree was laid across the bucket on a diagonal, and fit easily with only a bit of the tree hanging out the ends. The tree was light and relatively easy to transport. Although I was taking the tree to be converted into a wood chips, based on this experience I would be comfortable bringing home a new tree on the bike sufficiently unharmed.
Thanks to Kurt Ritchie for capturing the tree toss.
See more photos of Christmas-trees-by-bike in the comments of the page being linked to.