Medicinal Rhubarb Edible?

Thanks you very much for returning my call so promptly. As I mentioned in our conversation, I have found references to the stems/petioles of Rheum palmatum being not only edible, but actually superior in taste to "garden" rhubarb.
I am only concerned that the information I have provided, that Rheum palmatum is edible, is correct. I would not anyone to be harmed or misled by what I said.
I appreciate your offer to ask your Chinese herb specialist about this for me.

Our Chinese herbs specialist, Lisa Li, reports that none of her Chinese herb references refer to any of the medicinal rhubarbs (Rheum palmatum, R. tanguticum, R. officinale) being used in China as food. She herself never heard of anyone eating rhubarb for food. She did say though that a colleague of hers in Beijing told her that medicinal rhubarb is sometimes added to soups to take when one is sick, but the phone connection was lost before Lisa could get details.
That there is no common Chinese tradition of eating rhubarb, particularly the petioles as we do in the West, is curious. How much of that is a reflection of cultural taste differences or of something else is an interesting question. It would seem to me that a herb that is used so widely in China for medicinal purposes would have been adopted for food at some point in the thousands of years that rhubarb has been in use – if medicinal rhubarb is indeed good to eat. Even if it is not considered tasty by Chinese culinary standards, it would surely have been eaten as a "famine food" during times of food shortages – if it is safe to eat. That it appears never to have been adopted as a common food raises the possibility that the indigeneous rhubarbs are not safe to eat over the long term. [But see the note added below from Professor Lu about the traditional Tibetan usage of "da huang" or medicinal rhubarb.]
Both Lisa and I suspect that the practice of adding rhubarb to soup involves the root, not the petioles. But because the root is laxative it would not make nutritional sense to add rhubarb roots to food for long periods. Clearly the practice of adding rhubarb roots to soup would have to be limited to short periods, possibly for bowel cleansing or for the treatment of constipation.
Some of the links you list below refer to varieties that have been grown in Europe for a century or more as ornamentals. We are not confident that these varieties are identified correctly botanically. We have seen "Rheum palmatum" and "R. tanguticum" from European sources that did not conform to description. We feel that European plants with these names are likely to possess varying ancestries involving the common rhubarbs, Rheum rhabarbarum, R. rhaponticum, and R. x cultorum, as a parent at some time in the past. If our theory is true, such hybrids may in fact make excellent edible plants.
The history of rhubarb is a fascinating one. Because the Tibetan and western Chinese species were so highly esteemed in medicine, they were a valuable commodity on the trading routes between China and Europe for many centuries. Traders even tried to obscure the origin of the best roots by calling them "Turkish rhubarb" when in fact the roots merely passed through Turkey. There is an excellent history of rhubarb written by Clifford Foust called "Rhubarb: The Wondrous Drug" (Princeton University Press, 1992) that gives a nice account of the controversies and shenangans surrounding rhubarb and of the search for the true medicinal rhubarb.
One of Lisa's projects at Richters is to find authentic medicinal rhubarb seeds or plants from China and Tibet. Her work so far has revealed that even in China there is considerable confusion over the botanical identity of material labelled "R. palmatum" and "R. tanguticum". Most of the accessions we have received from western China have turned out not to conform to the classical descriptions of these species.

The links below are what I found that give any indication that this plant is edible – or at least not harmful. Thanks again.
Rhubarb originated in Asia, in particular China and Tibet, with the earliest records relating to its use dating back to 2700BC when it was mainly cultivated for medicinal purposes, in particular for its purgative qualities. Whilst it's believed that by the 1500s it was being used in Europe for its medicinal properties, one of the first records found of its culinary use in Europe dates back to 1608.? However, it was not officially recorded as a culinary plant in Europe until the mid/late 1700s and the plant used was probably a cross matching of Rheum rhaponticum, Rheum undulatum and possibly also Rheum palmatum.
The first rhubarbs introduced into Britain from China and Russia were grown as medicinal plants, the roots being used as a purgative. In the Victorian era the leaf stalks began to be used in pies and desserts and over 100 new cultivars were raised.
www.rhubarbinfo.com/rhubarb-background.html#TOC4 Leaf stem eaten raw or cooked. Superior in flavor to the common rhubarb and quite tender, has a long and proven history of herbal/medicinal usage?
www.hepatitis-central.com/hcv/herbs/fortheliver/rhubarb.html Leaves are not only edible but also taste wonderful in pies, compotes and jams. Root is added to tonic wines. (I THINK BY "LEAVES" THEY MEAN STEMS/PETIOLES...)
www.comp.leeds.ac.uk/cgi-bin/pfaf/arr_html?Rheum+palmatum+tanguticum&CAN=LATIND Leaf stem - raw or cooked[2, 7, 105, 183]. The stem is superior in flavour to the common rhubarb and quite tender[2]. An acid flavour, it is sometimes used as a cooked fruit substitute[K]. (Both say LEAVES are poisonous, but STEMS are edible)
www.rhs.org.uk/gardens/harlowcarr/harlowcarrnationalcollections.asp
www.motherearthherbs.com/rhubarb.html The root and stems of this plant are edible, but the leaves are poisonous due to their highly concentrated content of oxalic acid.
www.ansci.cornell.edu/plants/medicinal/rhub.html
www.recipes4us.co.uk/Specials%20and%20Holidays/Rhubarb%20origin%20uses%20recipes.htm Whilst their stems are never poisonous (unlike the leaves as mentioned above),? they do get "woody" late in the season, so pick whilst still tender.

[Additional comment from Professor Lu Rongsen of China, a specialist in herbs and special crops, excerpted from an email message dated May 7, 2002:]

Rheum palmatum is edible. In fact, the fresh young stem is often being eaten by Tibetan people, [as it has been] for thousands years. I was told that the fresh young stem has even been made into canned food.