Celery leaves are not only not poisonous, but they are good to eat. Indeed, in wild celery the stalks are discarded, and the leaves are eaten. All parts of the cultivated celery plant are edible and nutritious.
Most celery found in American supermarkets is the Pascal type, which is green. Other types of celery are white, which means they are either self-blanching or have been manually blanched. White celery tends to be a bit more tender and sweeter than green celery.
Celery contains antioxidants like vitamin C, vitamin A, flavonoids, dihydrostilbenoids and furanocoumarins. These antioxidants protect the body, including the blood vessels and organs, from damage by free radicals, which are oxygen molecules that steal electrons from other molecules.
Celery also has a very low glycemic index, which makes it beneficial to diabetics. It also has vitamin K, which is necessary for blood clotting, the essential mineral molybdenum, folate, potassium, fiber, manganese, phosphorus, magnesium, calcium and many of the B vitamins.
When buying celery, the stalks should be thick and crisp, and the leaves should be green and have a fresh and robust look about them. If the stalks are a bit limp, they can be revived by cool, fresh water.