Rhubarb

Rhubarb divides into two primary categories: field-grown and forced. Field-grown rhubarb, harvested outdoors from April to late June, features bright red to green stalks with robust tartness and deep green leaves—popular varieties include Victoria (speckled red-green stalks, vigorous producer), Canada Red (reliably crimson, cold-hardy), MacDonald (brilliant red, exceptionally tender), Valentine (deep red, minimal seed stalks), and Crimson Cherry (uniformly red throughout). Forced rhubarb, a Yorkshire specialty grown in heated dark sheds and harvested by candlelight from January to March, produces ethereal pale pink stalks with yellow-green leaves, offering a sweeter, more delicate flavor and meltingly tender texture. Green varieties like Goliath are highly productive but contain more oxalic acid. Glaskin's Perpetual, a heritage variety, can be harvested in its first year and has notably low acidity.

Rhubarb's story begins not in the kitchen but in the apothecary. For around two thousand years the Chinese have used the roots of Rheum species as medicine, prizing them as a powerful purgative. The dried root reached the Greeks and Romans by trade routes across the Volga, known in antiquity as the Rha, and in early modern Europe it could fetch more than cinnamon or even opium. The Romans imported these "barbarian" roots from beyond the Rha, giving us the Latin rhabarbarum and eventually our English word. Italian botanist Prosper Alpinus introduced culinary species to Europe in 1608, but rhubarb remained a medicine cabinet curiosity until the mid-18th century. The convergence of two factors transformed rhubarb's destiny: the plummeting price of Caribbean sugar and the accidental discovery of forcing in 1817, when workers at the Chelsea Physic Garden noticed that stalks covered by debris grew sweeter and more tender. By the Victorian era, the "Rhubarb Triangle" of Yorkshire—between Leeds, Wakefield, and Bradford—had become the world's forcing capital; its cold winters, which give the crowns the chilling they need before forcing, together with cheap local coal to heat the sheds and wool-industry waste used as fertiliser, made it ideal for forcing. Benjamin Franklin reportedly introduced rhubarb to America in the 1770s, though John Bartram was already cultivating it in Philadelphia decades earlier. Rhubarb remained a staple through the Second World War, but its popularity declined in the post-war decades as imported fresh fruit became widely available.

Rhubarb's signature pucker comes from oxalic acid, a compound that binds with calcium to form insoluble crystals—the same mechanism that makes the leaves toxic (leaves typically contain around 0.5–1% oxalic acid; stalks usually contain less, although levels vary widely with variety, age and season, and other leaf compounds such as anthraquinone glycosides may also contribute to the leaves' toxicity). This calcium-binding explains why rhubarb, despite containing decent calcium, is a poor dietary source of the mineral. The anthocyanins responsible for red coloration are pH-sensitive pigments that intensify in acidic environments and fade when diluted—hence the importance of minimal cooking liquid. Heat causes pectin breakdown and cell wall collapse, releasing water and creating rhubarb's characteristic jammy texture; cooking too long or at too high a temperature produces an unappetizing khaki mush. The Maillard reaction during roasting creates caramelized notes that complement the tartness. Interestingly, gut bacteria like Oxalobacter formigenes can neutralize dietary oxalates, explaining why some individuals tolerate high-oxalate foods better than others. Forced rhubarb's sweetness results from etiolation: deprived of light, the plant cannot photosynthesize, so it converts stored starch reserves into sugars, producing tender, less fibrous stalks.

Rhubarb is among the most sustainable crops available—a perennial that returns year after year without replanting, requiring minimal inputs once established. It thrives in cold climates with acidic soil, making it ideal for northern regions where other crops struggle. Major production areas include the United Kingdom, where Yorkshire Forced Rhubarb from the Rhubarb Triangle holds protected designation of origin status, Germany and the Netherlands, and in North America the Pacific Northwest and Michigan. When possible, source from local farmers' markets during peak season to minimize transportation impact and support regional agriculture. Forced rhubarb, while a remarkable tradition, requires heated sheds and significant energy input; consider it an occasional luxury rather than a staple. Home gardening remains the most sustainable option—a single crown can produce for 10–20 years, though it benefits from dividing every 5–10 years.