Here are some of my tips: Set the tree up without decorating it for a few days in order to give your cats time to adjust to it. This is a new adventure for the cats and having a tinkling, glittery tree is just too hard to resist. I always leave my tree undecorated for about three days after putting it up.
To secure the tree, invest in a heavy base. The base the tree comes with may not be sturdy enough so shop around for a strong one. I have an artificial tree but I use a large base meant for a live tree. I made a heavy wooden insert to place inside of the base and the tree stem sits in that. When I place the tree skirt around the tree no one can tell how big the base is.
When my cats were young, I decided the best way to prevent a toppling tree was to anchor it to the wall. I positioned the tree against the wall, in front of a large picture. I then removed the picture and secured the tree to the wall using fishing line and a strong hook. After Christmas I put the picture back and no one saw where the hook had been. If you have hanging plants, you can place the tree under that spot (remove the plant, of course) and tie the tree to the ceiling hook with fishing line.
When you begin to decorate, leave the bottom third of the tree plain to avoid temptation. Also, don't use tinsel because it's very dangerous for cats. When choosing ornaments, try to go for ones that won't be as tempting -- I stay away from lightweight ornaments that dangle too much. Before putting lights on the tree, coat the cords with bitter apple to prevent your cats from chewing them. I also thread the end of the cord through a piece of PVC tubing (painted green so it won't look too ugly) right where it plugs into the wall. I also use a special cord called a Smart Cord. Safe Living makes it and it shuts off the electricity to the cord should there be a break in the integrity of the wire
If your cats show an interest in the tree, place a corrugated cardboard scratching pad nearby. Also, make sure to grow some kitty greens for them. I've found if you place these objects near the tree, the cats tend to be less interested in chewing or climbing it. Also, never leave your tree lit when you leave the house or if you're going to be in another room
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