Buckwheat Family - Polygonaceae
R. Rhaponicum L. - Rhubarb - Edible stalks in spring and summer, though the leaves are considered poisonous.
Rheum palmatum is commonly known as Chinese rhubarb, and Rheum rhabarbarum (also known as R. rhaponticum) is commonly referred to as wild rhubarb in the U.S. Both plants belong to the family Polygonaceae. Rhubarb has very broad leaves and elongated, often reddish, petioles (leaf stalks).
The leaf stalks of rhubarb are edible,(See: Rhubarb Recipes) though the leaf blades are very toxic. The roots and rhizomes of R. palmatum and the roots of R. rhabarbarum are used in medicinal treatments. R. palmatum is considered a stronger medicinal than R. rhabarbarum. The most common medicinal use of these plants is as a laxative in humans.
See Rhubarb Recipes . One of the few foods available in the early spring, and loaded with vitamin C and nice tart flavor. Main uses are in Rhubarb Bread, and added to jams. One example: Rhubarb/Rasberry Jam, which is a great combination of sweet and tart.
The leaf blades of R. rhabarbarum are very toxic. They contain high levels of oxalic acid which can interact with blood calcium. Symptoms of oxalate poisoning in humans include: nausea, vomiting, abdominal pain, anuria, and hemorrhages. In ruminants (such as cows), oxalic acid can be degraded by rumen bacteria. The tolerance of ruminants to oxalate can be increased by gradually increasing the amount of oxalate in the diet. In general, however, oxalate is considered toxic to ruminants.
The active compounds (those that provide the laxative effect) in these plants also can cause side effects. Chronic consumption of anthranoid derivatives can turn urine a yellow or red color. Chronic use may also cause liver damage. During normal (non-chronic) use, anthranoid derivative laxatives cause increased losses of body water and electrolytes. Potassium loss may be responsible for symptoms such as a decrease in muscle activity and cardiac arrhythmia. There is some indication that chronic use of anthranoid derivative laxatives could be carcinogenic.
Uses and Efficacy
While Rheum spp. have definite laxative properties when used to treat human ailments, no scientific studies could be found proving its effectiveness in the treatment of livestock. In livestock, it is used as a treatment for diarrhea, chronic constipation, gastritis, anemia, nervousness, and lack of appetite. According to one source, the dose for livestock should be very small (1-2 roots, finely sliced). Also, some medicinal plant sources for humans and livestock recommend purchasing the powdered root versus trying to grow the plant and prepare the treatment at home.