While definitely off topic, the answer is likely thousands. Most wild edible guides advise against eating anything you're not sure about, and also provide tips for testing items you're curious about. First tip is to taste a little before you consume, and pay attention to sensations in your mouth. The vast majority of plants out there are simply unpalatable (tannins too high, too little digestible content). Most poisonous items you can consume will give you an upset stomach in … various fashions (tomato vegetative portions, green potatoes, pokeweed berries); only a handful can truly mess you up with organ failure, pulmonary depression, or cardiac arrest (datura, water hemlock, etc.)
There are a number of … objectionable edibles that require specific cooking methods; both acorns and skunk cabbage are edible after boiling in multiple changes of water. It is recommended that you cook any gathered mushroom before eating. Cooking is a Human superpower, along with language.