Many people are aware that certain holiday plants, such as mistletoe and holly are poisonous to pets but wheat about the most common holiday “plant,” the Christmas tree. We worry about pets tipping over the tree or tearing open presents but what about those pets that choose to eat the tree?
Christmas trees are considered to be mildly toxic. The fir tree oils can irritate the mouth and stomach, causing excessive drooling or vomiting. The tree needles are not easily digested; possibly causing GI irritation, vomiting, gastrointestinal obstruction or puncture.
Even thought the question refers to live trees, artificial trees are also dangerous when eaten. The principal thing to worry about are toxin release from the artificial material and intestinal obstruction (not digestible).
As noted, the amount of trouble depends on how much is consumed. Many times, pets do not consume mass quantities of tree material.
We would recommend confining your pets away from the tree when you are not home. This will allow you to be able to “supervise” any tree or plan eating activity.