Popular in pastries and baked goods, rhubarb is a slightly acidic vegetable that is more often than not modified into jams and pies in American culture. However, the stalks can also serve as a proper vegetable and are considered an emerging food by some contemporary dietitians. Beware of the leaves, which hold high concentrations of oxalic acid. This can lead to rhubarb leaf poisoning, symptoms being diarrhea and vomiting.