Rhubarb is a vegetable plant with imposing leaves in the centre of a thick, fleshy rib. Only this one must be consumed, the leaves very rich in oxalic acid can be the cause of poisoning. If the latter are still green, the ribs, of a length of 50 cm and the width of which varies between 3 and 7 cm, are red or green, depending on the varieties, and more or less acidic. Although it’s a vegetable, rhubarb is most often used sweet, as a fruit.
History of rhubarb
The term “rhubarb” is a deformation of the Latin rheubarbarum, itself derived from Rheum barbarum. Rheum was borrowed from the Greek Rha, which used to designate the Volga, on the banks of which the plant spontaneously grew. The expression Rheum Barbarum therefore meant “barbarian plant of the Volga”. Other authors believe the name comes from the Greek rheon, meaning “flowing”, referring to the purgative properties of the root. “Rhubarb” appeared in its present form at the end of the sixteenth century, but from the 13th century, the word “Reubarbe” was used.
The majority of the ten listed rhubarb species, including the one we grow in our gardens, come from China, Siberia, Mongolia and Russia. The use of rhubarb would be 2 700 years before our era, in China, where the medicinal properties of its root were taken. At the beginning of our era, the plant would have spread to western Europe, where it was also used for medicinal purposes. Its first food uses only date from the seventeenth century. It was reportedly introduced to North America in the early nineteenth century and was mainly used for making pies. This culinary tradition came from the Anglo-Saxon, who colloquially gave the rhubarb the name of pieplant (tart plant).
Rhubarb is now cultivated in many countries where the climate is relatively fresh. In areas where winters are not too rigorous, harvesting in the field lasts about 2 months. Some of the plants can be transplanted into the cellar in the fall in order to prolong the production.
With the rods, we make wine and, more recently, beers of micro-brewery. There is also an aroma for chefs. In Europe, the leaves are used to wrap cheeses and butter, and the root is given to pigs.
Rhubarb health profile
Rhubarb, with its highly tangy taste, would be better suited to salty dishes, although traditionally it is usually eaten as a dessert. Its high fiber content makes it a food of choice to maintain a good balance of blood lipids.
The benefits of rhubarb
Blood lipids. A study among patients with atherosclerosis (therefore at high risk for cardiovascular disease) showed regular consumption of rhubarb decreased total cholesterol and “bad” cholesterol (LDL). Another study showed daily consumption of rhubarb (bleached and then dried) could help to reduce total cholesterol and “bad” cholesterol (LDL) without harming the concentrations of “good” cholesterol (HDL). This work has been done with men with high blood cholesterol. The observed effect may be due in part to the soluble fibers present in rhubarb.
In animals, the addition of rhubarb fibers to a cholesterol-enriched diet resulted in a decrease in blood cholesterol. Rhubarb fibers, in particular insoluble fibers, would have the ability to bind to bile acids, favoring the excretion and absorption of fats.
Several prospective and epidemiological studies have shown that high consumption of vegetables and fruit decreases the risk of cardiovascular diseases, certain cancers and other chronic diseases. The presence of antioxidants in vegetables and fruits could play a role in these effects.
What does rhubarb contain?
The rhubarb stalk, which is the edible part of the plant, represents an important source of dietary fiber. The majority of its dry weight (74%) consists of fibers. Of these, insoluble fibers are 8 times more abundant than soluble fibers. Taking into account the dry matter, the rhubarb stem contains 5 times more total fibers than oat flakes (oatmeal) and roughly the same amount of soluble fiber. Soluble fibers (pectin, psyllium …) are recognized for their ability to decrease blood cholesterol while insoluble fibers (lignin, cellulose …) would help regulate intestinal function. Although rhubarb contains mostly insoluble fibers, some studies, both among humans and animals, have demonstrated the efficacy of rhubarb fibers in reducing blood lipids.
Rhubarb contains several compounds having demonstrated antioxidant activity, including polyphenols. Further research will be needed to determine the extent to which the consumption of rhubarb would be specifically beneficial to humans.
Oxalic acid (or oxalate) is a naturally occurring compound found in products of plant origin. This type of acid is known to bind to minerals such as calcium and magnesium. This could affect their absorption by the body. Although the rhubarb stem is rich in oxalic acid, it is not necessary to limit its consumption. Indeed, a study conducted among animals concluded the oxalate present in the rhubarb stem did not interfere with the calcium bioavailability of the food. In addition, in North America, as the consumption of rhubarb is rather marginal, its effect on mineral absorption probably has little impact on health.
Diet without oxalate. People at risk of lithiasis oxalocalciques (stones in kidney constituted of oxalate and calcium) should limit their consumption of foods rich in oxalate. Rhubarb is one of 8 foods having shown a capacity to increase oxalurie. It is therefore recommended for these people to avoid consuming them in order to prevent the formation of urinary lithiasis (or kidney stones).
Choice and conservation
Choose strong stems. When spliced, they should exude a dense sap.
Refrigerator. One or two weeks in a plastic bag.
Freezer. Cut the rhubarb into sections and freeze it or after you have briefly bleached it.
You can grow rhubarb by using seeds. However, it is preferable to purchase plant varieties having been selected for their organoleptic qualities and for their resistance to seeding. There are varieties with green, pink or red stalks. Gardeners and cooks generally prefer the latter, which are tastier.
Plant rhubarb in a nice corner in the garden, as it is a perennial plant that will produce for many years. Choose a place where the soil drips well to avoid the risk of crown rot or, if not, prepare an elevated border. Fill the planting hole with decomposed manure or compost. Space the plants 1 m to 1.5 m.
Water in case of drought and mulch plants. Do not harvest stems in the year of seeding and, in the 2nd year, harvest only for 1-2 weeks. Then you can harvest for 8 to 10 weeks, taking only one-third of the stems at a time. This will allow plants to continue their photosynthesis process and remain well robust. It is possible to make a second harvest in the fall on the plants you intend to eliminate the following year.
Cut the floral stems as soon as they appear throughout the season.
Each year, in late fall or early spring, add a layer of manure or compost near the base of the plants.
Divide the seedlings after 5 or 6 years by cutting the roots into 7 or 8 pieces, each with at least 1 bud. If possible, set up these new plants in a different place in the garden.
To avoid attracting the rhubarb weevil, eliminate the kinky patience, a wild rhubarb-like plant, which serves as a host. To reduce the risk of illness, remove the leaves in the fall when they have turned yellow.
Rhubarb plants can be forced into the cellar at a temperature of 10 °C to 13 °C. In the fall, take out the plants by leaving them a small clod of land and leave them on the ground so they will freeze for a few days or even weeks. Then put them in large pots or crates of wood and fill with soil or peat moss. It’s important to protect them from the light by ensuring the room is in full darkness or by covering them with black plastic. The first stems should appear five or six weeks later. We harvest them like we do in the garden. We can then keep the seedlings fresh, but sheltered from freezing, then retransplant them to the garden the following spring.
Ecology and environment
A natural insecticide
In organic farming, rhubarb leaves are used to make a particularly effective insecticide against aphids. We prepare an infusion in which we dilute a little soap and water the plants.
In the Morley region of England, the cultivation of rhubarb is a tradition that has been passed down from generation to generation since the beginning of the nineteenth century. Each year, we produce nearly a thousand tons for the sale in fresh market, for the freezing or for the manufacture of the famous English rhubarb jam. Global warming is a real threat to this culture. The plant needs a long period of cold before producing its stems. But over the last few years, the winter’s clemency has had the effect of delaying the harvest for several weeks. The production season is reduced as well as the harvest.