Rheum rhabarbarum

Rheum undulatum in Jardin botanique de la Charme

Rheum undulatum - Bergianska trädgården - Stockholm, Sweden - DSC00564

Rheum undulatum g1

Rheum rhabarbarum, commonly known as rhubarb, is a species of plant in the family Polygonaceae. It is a herbaceous perennial growing from short, thick rhizomes. The plant has large leaves that are somewhat triangular-shaped with long, fleshy petioles. The flowers are grouped in large compound leafy greenish-white to rose-red inflorescences. While the leaves are toxic due to the presence of oxalic acid, the fleshy stalks (petioles) are edible and are commonly used in cooking for their tart flavor.

Description

Rheum rhabarbarum grows to 2-3 feet tall and wide. The leaves of the plant can grow up to 2-3 feet in length, which makes it a significant presence in the garden. The underside of the leaves is often a lighter green than the top, and the whole leaf is covered in a fine, velvety down. The stalks, which are the only edible part of the plant, vary in color from red to pink to green. The plant blooms in late spring or early summer, producing flowers on tall spikes, though the plants are often harvested before they flower for culinary use.

Cultivation

Cultivation of Rheum rhabarbarum requires well-drained soil rich in organic matter. It prefers a full sun location but can tolerate partial shade. The plant is hardy in USDA zones 3-8. Rhubarb can be propagated by seed or more commonly by crown division in early spring. Care should be taken to ensure that the crown is planted at the correct depth to prevent rot. Rhubarb is a low-maintenance plant but requires regular watering during dry periods and a top dressing of compost or manure in spring.

Culinary Uses

The stalks of Rheum rhabarbarum are famously used in pies, tarts, and jams, often sweetened to counteract their natural tartness. Rhubarb can also be used in savory dishes, pairing well with fatty meats and fish. It is a traditional ingredient in British and Scandinavian cooking and has gained popularity in North American cuisine. The stalks are typically harvested in spring and early summer.

Toxicity

The leaves of Rheum rhabarbarum contain high levels of oxalic acid, which is toxic to humans and animals if ingested. The toxic effect can range from mild nausea and vomiting to more severe symptoms such as difficulty breathing and kidney failure in extreme cases. Only the stalks should be consumed, and all parts of the leaves should be discarded.

Cultural Significance

Rhubarb has a long history of cultivation, dating back to ancient China where it was grown for medicinal purposes. It was not until the 18th century that it became popular in Europe as a food item. In some cultures, rhubarb is celebrated in festivals and culinary competitions, highlighting its importance in local cuisine.

Conservation

As a cultivated plant, Rheum rhabarbarum does not face any immediate threats of extinction. However, maintaining genetic diversity within cultivated rhubarb is important for the resilience of the species to pests, diseases, and changing climate conditions.