Decorating and Design - Artificial Tree in Terra Cotta Pot

I'm not sure where to post this. I've been seeing this look in magazines, but I'm not sure how to keep the tree in the pot from tipping. I bought a 6 or 7 foot narrow tree last year. Diameter at bottom might be about 3 ft. What size pot do you think I would use. I've hear to fill it with sand, but I'm afraid that won't keep it from tipping. Any suggestions?

If it is a tree that does not disassemble for storage, perhaps permanently setting in plaster of Paris would be a permanent solution. For a temporary solution pea gravel or other type of gravel could be a solution. Gravel is heavier than sand and the tree would be less likely to shift. For pot size, aesthetically approximately 1/3 the size of the tree at its base. If 3 ft. wide, then a 12" pot and certainly nothing larger than 18".

i think maybe a 12" pot for a 7 foot tall tree would be too small looking & the tree would surely tip over as there wouldn't be enough room to hold enough gravel to prevent tipping. i'd go with one of those really big pots that's about 24" across & deep. to be realistic looking, the root ball of a tree that size would surely take a pot that size, right? how big do the pots in the magazine pictures appear to be?