Is it a fruit or a vegetable? In jam and crumble we use Rhubarb like a fruit but as it is not produced from flowers it is not a fruit in any botanical sense but is not a typical vegetable either!
The part we eat is technically the leaf stalk or petiole, which contains oxalic acid and other compounds giving rise to the bitter taste. These compounds are more concentrated in the leaves, which are poisonous and should not be eaten.
Rhubarb became popular as a food only since the 17th century, when sugar became widely available and reasonably cheap.
Botanically, Rhubarb is of hybrid origin with a latin name Rheum x hybridum, belonging to the family Polygonaceae which also contains our familiar Docks and Bistorts.
Long before it was used as food, it was an important medicinal plant in Asia, and in China was recorded in herbals as long as 2,700 years ago
Its origin was in Central Asia, in the area of the Volga River. From here it was transported along the Silk Route to China and the Middle East, reaching Europe by the 14th century.
There are about 60 wild species in the genus Rheum, and a few of these such as Chinese Rhubarb (Rheum palmatum) are cultivated as ornamental herbs for their large sculptural leaves and colourful flower spikes.
Perhaps the most spectacular kind is the Giant Himalayan Rhubarb (Rheum nobile) found at 4,000 to 5,000 metres throughout the Himalayan mountains.
It grows on rocky slopes and cliff ledges where from a distance appears like miniature white spaceships up to six feet high.
Its lower leaves are green like a typical rhubarb, but the huge flower spike is covered by white translucent ‘bracts’ covering the tiny flowers.
The botanist Joseph Hooker discovered it in the Sikkim Himalaya in 1849 and wrote about it in his Himalayan Journals (1854): ‘On the black rocks the gigantic rhubarb formed pale pyramidal towers a yard high, of inflated reflexed bracts, that conceal the flowers, and over-lapping one another like tiles, protect them from wind and rain.’
It is thought that the bracts protect the flowers from high levels of UV radiation, and also create a greenhouse effect, heating the air around the flowers to speed up pollination and seed production in the hostile climate.
The plant is difficult to grow in cultivation, but in 1880 it was successfully grown in the Royal Botanic Garden Edinburgh for the first time in Europe and caused something of a sensation at the time.
The next evening meeting of the Scottish Wildlife Trust in Duns is tonight at 7.30pm in Duns Parish Church Hall when Jim Wilson will talk and show his images of ‘Scottish Landscapes and Wildlife’
Guests and visitors are very welcome.