Here's our how-to:
2 large heavy urns (I found the large urns at Michaels on sale! Make sure they're heavy.)
2 bags of sand
tree branches with two at least 7' or more (depending on the size of arch you want) We used maple branches from our backyard. You don't want anything too bendy as it won't hold itself up.
wire (I used bind wire which is a paper wrapped wire -you can get from a florist or Michaels sometimes)
crowning glory (again you can get this from a florist)
Position your two tall branches in each urn. Have someone hold them in place while you add sand. Lean them together and attach with wire. Trim off odd branches. Add short branches to fill in the base.
I sprayed the whole thing with tons of crowning glory, which helps maintain moisture.