We're creating a float for our Christmas parade this year and were unsure the best way to secure a plastic Christmas tree :)
I would just use a couple of cinder blocks and tie it off from the top, middle, and bottom of the tree to the cinder blocks, and maybe reinforce the trunk with a yardstick or broomstick affixed somehow to the cinderblocks
What are you securing it to...meant is the float a wagon bed, a truck bad, the back of a car? What/how your float is being built will determine your best solution. Post back with more details as each transportation method would have a different solution!