I got this tip from my Dentist:
Put a hook (screw-in type) into a stud (if you can find one, otherwise use wall anchor) - and use DENTAL FLOSS tied to the hook and wrapped around the trunk - and that sucker will NOT fall down.
It works for middle-of-the-room trees, too - hook in ceiling, though.
I had a 50 LB Lab, and she loved running and bumping into the tree, but it never fell after I saw my dentist.
I mean, have you ever tried to rip dental floss without a cutter? It ain't happenin'!
Put a hook (screw-in type) into a stud (if you can find one, otherwise use wall anchor) - and use DENTAL FLOSS tied to the hook and wrapped around the trunk - and that sucker will NOT fall down.
It works for middle-of-the-room trees, too - hook in ceiling, though.
I had a 50 LB Lab, and she loved running and bumping into the tree, but it never fell after I saw my dentist.
I mean, have you ever tried to rip dental floss without a cutter? It ain't happenin'!
to do this. However we use craft wire.
It was huge!! Filled the entire area in front of the bay window. One night, I wake up and DH isn't next to me. I get up to find him trying to upright the tree which feel and left broken ornaments all over the room.
A bit of dental floss did the trick to keep it upright. 
