Chaya – a native Mexican shrub – is also called the spinach tree because its cooked leaves taste similar to spinach. Cooked chaya actually beats spinach when it comes to nutrient content. It's a better source of protein, calcium, and iron, for example [source: Weil].
It's actually pretty rare to run across chaya at all in most parts of the world. There are people growing it in Florida, Texas, and parts of Mexico, but cooking with it has become uncommon [source: Weil]. That doesn't mean you can't safely cook chaya!
Like with cassava and bitter almonds, hydrogen cyanide is the danger when eating raw chaya. And like these other foods, sufficient cooking renders the leaves safe to eat. You can season it just as you would any leafy green vegetable. To cook chaya, just boil the leaves for 20 minutes on the stove, and make sure that you don't inhale the cooking fumes or steam, and that the pan you're using isn't aluminum; chaya plus aluminum equals explosive diarrhea [source: Deane].