Rhubarb - Rheum rhabarbarum

Common Names: Rhubarb, Garden rhubarb, Curly rhubarb, Wavy-leaf rhubarb, Rheum rhabarbarum, rhabarber (German), rhubarbe (French), ruibarbo (Spanish), Tai Huang (Chinese), Da Huang, Radix et Rhizoma Rhei (pharmacological/Latin), rheum, rewandchini, rabarbara (Italian), rhubarb root

Latin Name: Rheum rhabarbarum

Origin: Asia, Australia, Europe, South America, North America

Short Introduction

Rhubarb prefers sunny locations and does not thrive as well in colder climates (such as the United Kingdom, Ireland, or Russia). This hardy plant is cultivated worldwide, with potential for year-round harvest using greenhouses, which results in juicier and sweeter stalks compared to those grown outdoors. The outdoor variety is among the first crops ready for harvest in the temperate zones of the northern hemisphere (usually between late April and May). In the southern hemisphere, it is commonly harvested between October and November. In the northwest United States, harvest occurs twice per year, first in late April/May and again between June and July.

Detailed Description

This magical kitchen herb is a beloved staple and also featured in the famous Swedish bitters!

Botanical Information

Rhubarb (Rheum rhabarbarum) is a robust, perennial plant reaching up to 3 meters in height. Its green, hollow stems can be up to 6 cm in diameter, are smooth, and typically support the plant's flowering structure. The basal leaves are large, up to 60 cm long, light green, rounded to oval or elongated, with a smooth underside and a scalloped, sometimes colored petiole (ranging from whitish to green or red). The inflorescence is a terminal panicle, about 15–35 cm long. Flowers are bisexual, yellow, with a six-parted, deciduous perianth about 2 mm long; blooming usually occurs from late June to early July. The fruit is a winged, ovoid achene up to 8 mm in length.

Origin and Distribution

Rhubarb's original homeland is believed to be Central or Eastern Asia, specifically regions of Mongolia, Eastern Siberia, and certain provinces of China. The plant grows best in calm (or mountainous) climates such as Syria and Turkey as well. In Europe, it occurs from the far eastern part of Russia to the westernmost parts of the continent. From there, rhubarb spread to North America (USA, Canada), and is most widely cultivated in Bolivia and New Zealand. In many countries, notably the Czech Republic, rhubarb is commonly grown both in gardens and found in the wild.

Usage / Dosage

In China, rhubarb has been used in traditional medicine for millennia and is cited in historical medical texts. There are references, possibly as early as Dioscorides, noting rhubarb’s medicinal uses. The plant was imported to Europe by way of the Silk Road, through Turkish and Muslim ports such as Aleppo and Smyrna, and alternatively via Russia. Due to the hardship of transport, it became—along with cinnamon, opium, and saffron—a rare and valuable imported spice and medicine. High public and pharmacy demand stimulated cultivation within Europe, where it became widely grown and eventually reached North America.

Only the leaf stalks are consumed, prized for their strong, tart flavor. These stalks must always be cooked—never eaten raw—and are usually cut into small pieces and stewed or cooked in water with sugar until tender. The cooled, cooked rhubarb is served as a dessert or mixed with flour for pies, frequently added to curd cakes, fruit dumplings, compotes, jams, cakes, or even soups. Due to its oxalic acid content, aluminum cookware should not be used when cooking rhubarb, as the acid can dissolve aluminum.

The leaves contain various anthraquinones (such as rhein and emodin), which have a mild laxative and cleansing effect. For this reason, rhubarb is used for mild constipation. In folk remedies, it is commonly recommended for digestive problems. Several medical case studies have described doctors using rhubarb for certain ailments. Clinical and preclinical studies often focus on the positive effects of rhubarb’s active substances in potential treatments for various gastrointestinal disorders, including chronic or acute constipation. In a smaller study, the bioactive compounds found in rhubarb, in combination with ten other medicinal plants, improved kidney function in patients with glomerulonephritis after three months of regular use.

Rhaponticin, also found in all parts of the plant, showed anti-hyperglycemic effects in vivo in diabetic animals. One clinical study indicated a notable decrease in total cholesterol and LDL cholesterol in patients with high cholesterol. Another smaller clinical study showed some benefit in weight reduction among obese subjects, given regular rhubarb-containing herbal blends along with moderate exercise.

In various parts of the plant, the pigment parietin has been identified. This compound has a proven anti-leukemia effect in vitro, inhibiting the growth and development of human leukemia cells by about 50% within 2 days. In vivo, over 11 days, it eliminated about two-thirds of one type of lung cancer cell. The exact pharmacological mechanism is still under investigation, but parietin remains a subject of scientific interest.

Emodin, isolated from rhubarb, has been shown in vitro to inhibit the production of nitric oxide, interleukins 6 and 1-beta, without observed toxicity or tissue damage. The overall effect is a suppression of pro-inflammatory factors by inhibiting the activity of relevant genes and signaling molecules, thus confirming anti-inflammatory properties of rhubarb’s active compounds.

Some reports suggest potential uses for rhubarb preparations in the treatment of oral ulcers, herpes, and possibly gastric bleeding. A small clinical study noted a beneficial effect of rhubarb, alone or in combination with captopril (an antihypertensive drug), in poor kidney function, recommending its use in the management or prevention of renal failure.

Folk Medicine

In both traditional Arabic and European medicine, regular consumption of rhubarb (or foods prepared from it) has been recommended for various forms of constipation, nasopharyngeal infections, and even to ease the symptoms of gonorrhea. In Traditional Chinese Medicine, it is frequently combined with other herbs for impaired liver function in non-alcoholic patients. In folk medicine, rhubarb is also given to help control high blood pressure during childbirth and to decrease risk of severe complications from untreated sepsis. In some cases, rhubarb was given after surgery, with observed acceleration of recovery and improved healing processes.

Active Compounds

Rhubarb contains a wide range of bioactive compounds, most notably anthraquinones including rhein, emodin, and their derivatives (e.g., glucorhein glycosides), along with parietin pigment and others. These substances exert mild laxative and cleansing effects, thus rhubarb is mainly used for constipation. Other components include the stilbenoid rhaponticin, flavanol glycosides (e.g., catechin-O-glucosides), quinone molecules, unsaturated alcohols, aldehydes, methylbutanol, butanone, hexanoic and oxalic acid, among others.

Traditional Dosage

Depending on the intended therapeutic use, rhubarb extract has traditionally been given in doses of 23 mg/g, 2–4 times daily for approximately 14 days to calm oral ulcers and cold sores. During World War I, several cases of "poisoning" (vomiting, diarrhea) occurred in Britain from rhubarb after it was mistakenly recommended as a regular vegetable or fruit. This led to elevated oxalic acid levels and associated toxic reactions. The maximum toxic level for oxalic acid is reported as 375 mg/kg for animals or 25 grams for a 65 kg human, which is much higher than the content typically found in rhubarb stalks. Nevertheless, rhubarb should always be consumed in moderation.