To connect the pumpkins and anchor the topiary in the urn, recycle the handle ofan old rake or broom. You need it to be long enough to anchor to reach the bottom of the pot and extend up through the pumpkins. No handle? You could also use some steel or pvc pipe.
Spray your pumpkins with some acrylic varnish to seal out the elements and help your display last through the fall. Let them dry completely.
In the meantime, wash the broom handle with a mild bleach and water solution. This will kill any germs on the pipe and protect the pumpkin from rotting out from inside.
When your pumpkins are dry, use a drill and a spade bit the same width as your pipe to drill holes in the top and bottom of the large and medium pumpkins. Only drill a hole in the bottom of the small pumpkin. Use a cloth to wash the holes with the bleach and water.
Insert the handle into the urn and push it as far down into the soil as you can. Then thread a large black garbage bag onto the pipe.
Even though you're putting a hole in the bag, you'll be able to pull it up and over the topiary when you need to discard the pumpkins and it will be a lot less messy than if you didn't have it. Just tuck the bag inside the urn, it will be hidden by the biggest pumpkin.
Then, thread the pumpkins one by one onto the pipe and you're all set. You can leave it just the way it is or you can add leaves or other decorations! I'm Mrs. Fixit and it's just that simple!