Is Chinese Rhubarb safe to eat?

Chinese Rhubarb - Rheum Palmatum Tanguticum

Last weekend I bought the plant shown above from Ashdale Nursery, who specialise in perennial and cottage garden plants. The reason I bought it was that I vaguely remembered it was edible, and because it didn't cost too much. Since then, though, I've googled the plant and found a lot of contradictory information.

On one side are a number of forest garden and permaculture sites. For example, PFAF has this to say:

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].

 Similarly, the same plant is being sold by Martin Crawford with the following description:

Rhubarb (Rheum palmatum) Turkish

Rheum palmatum. A large perennial from Mongolia, growing to 1.5 m (5 ft) across and 3 m (10 ft) high with very large leaves. Grow in any moist, well-drained soil in sun or shade. Makes a good ground covering plant, and the leaf stalks are edible in the same way as ordinary rhubarb, with a superior flavour; the roots are used medicinally. Hardy to -20ºC.

Rhubarb (Rheum palmatum tanguticum) Turkish Red

A variety of Turkish rhubarb with reddish stalks and leaves.

The Gardeners' World website also explicitly says that the plant is edible:

The large, jagged leaves of this rhubarb bring architectural drama to a moist pond edge. As well as being a valuble ornamental plant, its red stems are full of flavour, making this a variety well worth growing as an edible crop. Divide the rootstock in spring with a knife, leaving one bud on each division, or sow seed in autumn.

On the other hand, Wikipedia makes no mention of the leaf stems being edible (although it does discuss medical uses of the root and rhizomes), and a number of sites selling this species as an ornamental explicitly warn that it shouldn't be eaten. For example:

 Please note: this is an ornamental plant that does not offer any edible produce. Although it is related to the common garden rhubarb plant, it does not produce the same edible red stems. This plant has no edible parts and the leaves are actually poisonous if consumed, as with all varieties of rhubarb.

I am inclined to trust PFAF and Martin, but I think perhaps the first time I will try a small amount just to make sure.