If you are going to put twigs in your mouth it is probably a good idea to learn which common ones to avoid...poison ivy/oak being the obvious and fairly ubiquitous one, but Blue Elderberry is another that is common in the West. You can eat the cooked berries but otherwise all parts of the plant are toxic.

Probably even better to learn which ones are safe in the area in which you will travel.

The best of course is to just take a toothbrush and some regular toothpaste and just take care where you expectorate!