🍰 The half you throw away

A rhubarb plant grows enormous leaves on top of thick red-green stalks, and only one of those two things is food. University of Minnesota Extension gives the rule in three short sentences, with no hedging in it at all: “Rhubarb leaves are toxic. Do not eat them. Only the long, thick leaf petioles, the ‘stalks,’ are edible.” The stalks are ferociously sour, so they are nearly always cooked with sugar — which is where the plant’s old nickname comes from. Extension still uses it: rhubarb is a “pie-plant,” because “you can cook, sweeten and use the chopped stalks as a pie filling.” A crop where you harvest the handle and discard the leaf is an unusual bargain, and gardeners make it every spring.

Basis: University of Minnesota Extension, “Growing rhubarb in home gardens” (author Jill MacKenzie, reviewed 2024): “Rhubarb leaves are toxic. Do not eat them. Only the long, thick leaf petioles, the ‘stalks,’ are edible.”; “Rhubarb is also a ‘pie-plant,’ because you can cook, sweeten and use the chopped stalks as a pie filling.”

The reason is a chemical the plant keeps most of in its leaves: oxalic acid. And this is one of those rules a whole country has already tested the hard way. NDSU Extension tells the story in two sentences: “During the World War I food shortages, people were encouraged to consume rhubarb leaves as a vegetable. That was not a good idea because oxalic acid is found in abundance in the rhubarb leaves.” Wartime advice, given with good intentions, about a plant everybody already had in the garden — and wrong. The advice today is much shorter. “Do not eat any rhubarb leaves and you will be fine,” writes NDSU’s food and nutrition specialist; the stalks in a pie, says Minnesota Extension, are a different matter, because “eating an occasional dish containing rhubarb does not pose a serious nutritional threat.”

Basis: NDSU Extension, “Prairie Fare: Can Rhubarb Become Toxic?” by Julie Garden-Robinson, Food and Nutrition Specialist: “During the World War I food shortages, people were encouraged to consume rhubarb leaves as a vegetable. That was not a good idea because oxalic acid is found in abundance in the rhubarb leaves.”; “Heed the earlier warning: Do not eat any rhubarb leaves and you will be fine.” University of Minnesota Extension, “Growing rhubarb in home gardens”: “Eating an occasional dish containing rhubarb does not pose a serious nutritional threat.”

Rhubarb also took a very long road to the pie dish, and for most of that road nobody was eating it. Wisconsin Horticulture’s account runs like this: the plant is “native to southern Siberia,” and “it got its name from the Russians who grew it along the Rha River (now the Volga).” Long before it was a dessert it was a medicine, at least as these Extension accounts tell it: “the ancient Chinese used it as a medicinal herb over 5,000 years ago,” the same page says. And the stalk was not even the first part anybody ate. Illinois Extension records that “the first crops were grown for the round pouch of unopened flowers, which was cooked as a delicacy (in northern Asia it is still raised for this purpose).” Europeans, when they finally tried eating it, started at the wrong end: “the English were the first to eat rhubarb, beginning in the 17th century, but unfortunately chose to begin with the leaves that look like chard.” Only “by the late 18th century” had they “discovered that the tart stalks were the part to eat – perfect for ‘tarts’ giving rise to the nickname ‘pieplant’.” It reached this country soon after: “it was brought to the Americas by settlers before 1800.”

Basis: Wisconsin Horticulture (University of Wisconsin–Madison Division of Extension), “Rhubarb, Rheum rhabarbarum”: the quoted sentences on its Siberian origin, the Rha River name, the ancient Chinese medicinal use, the English beginning with the leaves, the late-18th-century switch to the stalks and the nickname “pieplant,” and its arrival in the Americas before 1800. Illinois Extension, “Rhubarb” (Home Vegetable Gardening): “Only the stems are edible, although the first crops were grown for the round pouch of unopened flowers, which was cooked as a delicacy (in northern Asia it is still raised for this purpose).” The historical statements are reported as those Extension publications give them.

Here is the part that surprises people who think of it as a fruit: rhubarb is a vegetable, and it is a relative of a grain crop. Minnesota Extension files it plainly — rhubarb is “a perennial vegetable hardy enough for Minnesota gardens,” and “it is in the buckwheat family, has a sour flavor and is among the first crops ready for harvest in spring.” Perennial is the important word. You do not sow rhubarb every year; you plant a crown once and then wait, because Extension’s instruction is to “wait until the second season before harvesting,” and “wait until the third season if you started from seed.” After that the same plant can keep going for a very long time — “the plants can live fifteen or more years with good care.” A rhubarb patch is less like a vegetable bed and more like a small tree that happens to make pie.

Basis: University of Minnesota Extension, “Growing rhubarb in home gardens”: “Rhubarb (Rheum rhabarbarum) is a perennial vegetable hardy enough for Minnesota gardens. It is in the buckwheat family, has a sour flavor and is among the first crops ready for harvest in spring.”; “Wait until the second season before harvesting. Wait until the third season if you started from seed.”; “The plants can live fifteen or more years with good care.”