Rhubarb
Rheum rhabarbarum
Rhubarb (Rheum rhabarbarum) is a robust perennial plant in the family Polygonaceae, grown for its thick, fleshy, crimson-green leaf stalks (petioles) that are cooked as a fruit in pies, crumbles, jams, and desserts — despite technically being a vegetable. While the stalks are a beloved culinary ingredient with a distinctive tart, fruity flavor, the leaf blades contain dangerously high levels of oxalic acid and are TOXIC to humans.
• A vegetable legally classified as a fruit in the United States (1947 tariff ruling by the U.S. Customs Court)
• The stalks contain far less oxalic acid than the leaves — safe to eat when cooked
• Has been called the "pie plant" for over 200 years due to its primary culinary use
• The genus Rheum contains approximately 60 species, mostly from Asia
• Rhubarb roots were used medicinally in China for over 5,000 years before the stalks were eaten as food
• Forced rhubarb (grown in darkness) produces sweeter, more tender, bright pink stalks
• Wild ancestors occur in Siberia, Mongolia, and the Tian Shan mountains of Central Asia
• Rhubarb root ("da huang" or Turkey rhubarb) was traded along the Silk Road for millennia as a valuable medicinal
• The species was likely first domesticated for its medicinal roots in China, not for food
• Introduced to Europe in the 14th century via the Silk Road and Russian traders
• First grown as a food plant in 18th-century England
• Became extremely popular in Victorian England as a pie filling
• First described by Linnaeus in 1753
• The "rhubarb triangle" in West Yorkshire, England, is famous for producing forced rhubarb
• Now grown commercially in Europe, North America, and parts of the Southern Hemisphere
Roots:
• Large, fleshy, deep taproot system
• Internal color yellow to orange
• Rich in anthraquinone compounds (medicinal)
Leaves:
• Very large, broadly ovate to almost circular, 30 to 60 cm in diameter
• Dark green, palmately veined, crinkled surface
• margins wavy to slightly lobed
• The leaf BLADES are TOXIC — high in oxalic acid
• Petioles (leaf stalks): the edible portion, 30 to 50 cm long and 2 to 4 cm thick
• Petioles green to crimson-red, fleshy, crisp, tart
Flowers:
• Small, white to greenish-white, 5 to 8 mm
• Born in large, tall, branching panicles 1 to 2 meters high
• Six tepals in two whorls
Fruit:
• Small, three-winged achene, 8 to 12 mm long
• Brown, containing a single seed
• Rare in cultivated varieties
Habitat and Natural Range:
• Wild Rheum rhabarbarum grows in the cold, semi-arid mountain valleys and alpine meadows of Siberia, Mongolia, and the Tian Shan range of Central Asia at elevations of 1,000 to 3,500 meters
• Prefers deep, fertile, well-drained alluvial soils along stream banks and in moist depressions, often growing alongside other cold-adapted perennials
• Naturalized populations exist across northern Europe and North America, where it has escaped from cultivation and established in cool, moist habitats
• Requires a pronounced cold period (vernalization) for proper spring emergence — the plant is genuinely cold-dependent, not merely cold-tolerant
Pollination and Reproduction:
• Flowers are primarily wind-pollinated; the tall, branched panicles (1 to 2 meters high) rise well above the foliage canopy to maximize pollen dispersal
• Various species of flies, small bees, and beetles visit the nectar-rich flowers as secondary pollinators
• Each mature plant can produce thousands of three-winged achenes that are dispersed by wind across considerable distances
• Vegetative spread occurs slowly through crown expansion, with established clumps reaching 90 to 150 cm in diameter over 10 to 15 years
Ecological Interactions:
• The massive leaves (30 to 60 cm in diameter) create dense shade that suppresses competing herbaceous vegetation beneath
• High oxalic acid concentrations in leaf blades serve as an effective chemical defense against most herbivores and insect pests
• The deep taproot system (reaching 1 to 2 meters into the soil) accesses subsoil moisture and nutrients, providing resilience during dry periods
• In native habitats, the large crown structure provides shelter for ground-dwelling invertebrates and small vertebrates
Seasonal Dynamics:
• Among the first perennial plants to emerge in spring, often appearing while snow still covers the ground, fueled by stored reserves in the fleshy root system
• Rapid spring growth produces the full leaf canopy within 4 to 6 weeks of emergence
• Flowering occurs in early to mid-summer, with seed maturation by late summer
• Complete above-ground dieback by mid-autumn, with the plant entering winter dormancy beneath snow cover
• Per 100 g raw stalks: approximately 21 kcal, 0.9 g protein, 0.2 g fat, 4.5 g carbohydrates
• Good source of dietary fiber (1.8 g per 100 g)
• Contains vitamin C (8 mg per 100 g), vitamin K, and small amounts of B vitamins
• Provides calcium (86 mg per 100 g), potassium (288 mg), and manganese
• Contains moderate amounts of magnesium and phosphorus
• Rich in beneficial polyphenols including anthocyanins (in red varieties)
• Contains lutein and zeaxanthin (eye-healthy carotenoids)
• Very high water content (approximately 94%)
• The leaf blades contain extremely high levels of oxalic acid (0.5 to 1.0% by weight) and soluble oxalates
• Ingestion of rhubarb leaves can cause oxalic acid poisoning: nausea, vomiting, abdominal pain, kidney damage, and potentially death in severe cases
• The stalks contain much lower levels of oxalic acid and are safe to eat
• Anthraquinone glycosides in the roots have strong laxative effects
• The roots should not be consumed as food
• Keep leaves away from children and pets
• Always remove and discard the entire leaf blade, keeping only the stalk
• Cooking does not eliminate the oxalic acid in leaves
• Crown division is the standard method: divide in early spring or autumn
• Each division should have 1 to 3 healthy buds (eyes) and a portion of root
• Plant crowns 5 to 8 cm below soil surface, 90 to 120 cm apart
• Seed propagation is possible but slow and does not produce true-to-type plants
• Prefers deep, fertile, well-drained soil rich in organic matter
• pH 6.0 to 6.8 is ideal; tolerates slightly acidic conditions
• Requires full sun to partial shade
• Consistent moisture is important; mulch heavily
• Do not harvest stalks the first year after planting
• From the second year, harvest for 4 to 8 weeks in spring
• Remove flower stalks immediately to maintain leaf production
• Plants are productive for 10 to 15 years
• Rhubarb stalks are most famously used in pies — "rhubarb pie" is a classic dessert in Britain and North America
• Made into crumbles, crisps, and cobblers (often paired with strawberries)
• Cooked into jams, preserves, and compotes
• Used in sauces, similar to applesauce
• Made into wine, cordials, and cocktails
• Rhubarb stalks can be candied or made into rhubarb chutney
• Traditional English rhubarb crumble is one of Britain's most beloved desserts
• In Scandinavia, rhubarb soup is a traditional summer dessert
• Young, tender stalks can be dipped in sugar and eaten raw
• Used in savory applications in some Asian cuisines
Fun Fact
• In the famous "Rhubarb Triangle" of West Yorkshire, England, farmers still grow forced rhubarb using methods unchanged since the Victorian era — the plants are transferred from cold fields into dark, heated sheds and harvested entirely by candlelight, because any exposure to light would cause the precious pink stalks to turn green and tough. The forcing sheds are so quiet that workers can literally hear the stalks creaking and popping as they elongate up to 2.5 cm per day in the darkness, a sound described as like "the sighing of the earth." This traditional forcing industry has been granted Protected Designation of Origin (PDO) status by the European Union • Rhubarb occupies a unique legal classification in the United States — in 1947, the U.S. Customs Court officially declared rhubarb a fruit for the purposes of import duties and regulations, because that is how it is predominantly used in American kitchens. Botanically it remains firmly a vegetable, making rhubarb one of the very few plants in history to have its identity legally redefined by an act of government — a vegetable by science, a fruit by law • The ancient Silk Road trade in rhubarb root ("da huang" or Turkey rhubarb) was so extraordinarily lucrative that it rivaled the tea and spice trades in economic importance. Chinese rhubarb root was considered so valuable as a medicinal that in 18th-century Imperial Russia, the czar maintained a strict government monopoly on all rhubarb imports, and smugglers caught illegally trafficking rhubarb root could face severe punishment. At its peak, rhubarb root was worth several times its weight in tea • In the town of Wakefield, West Yorkshire — the heart of the Rhubarb Triangle — the annual Wakefield Rhubarb Festival celebrates this remarkable plant with rhubarb-themed everything: rhubarb wine, rhubarb beer, rhubarb cheese, rhubarb jam, rhubarb chutney, and even rhubarb ice cream. The local combination of nitrogen-rich soil, cold winters, and centuries of traditional forcing expertise produces what many connoisseurs consider the finest rhubarb in the world, and the region once produced over 5,000 tonnes of forced rhubarb per year at its peak
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