Rheum palmatum Seeds | Ornamental Rhubarb
LATIN NAME: Rheum palmatum
COMMON NAME: Ornamental Rhubarb
Plant Profile
Rheum palmatum is the rhubarb of the herb garden and of the ornamental border, and it is a plant of scale. The leaves are huge, deeply lobed and red-veined, up to a metre across, and they rise on thick red stalks from a woody crown. In early summer it sends up a flower spike two metres tall, covered in small cream or pink flowers, and the whole plant looks tropical in a temperate garden.
The species grows in the mountains of western China and Tibet, between about 2,500 and 4,000 metres, on open slopes and in scrub. The root is thick and yellow inside, and it is the source of the rhubarb of Chinese pharmacy, which is a different drug from the garden rhubarb of the kitchen.
Science & Biotechnology
The root contains anthraquinones, chiefly emodin, chrysophanol and rhein, together with tannins and stilbenes. The anthraquinones are purgative, and the tannins are astringent, which is why the drug has a dual action and why the dose matters. The root also contains oxalates, and the leaf blade contains enough oxalic acid to be toxic.
The garden rhubarb of the kitchen is Rheum rhabarbarum and its hybrids, and only the stalks are eaten. The leaf blade of any rhubarb should not be eaten, since the oxalate can cause kidney damage. The ornamental species is grown for the foliage, and the root is not used in Western medicine, though it appears in Chinese formulas.
Uses & Benefits
In Chinese medicine the root is used as a purgative for constipation and for clearing heat, and it is included in formulas for jaundice and for ulcers. It is a strong drug and is not taken in pregnancy or during breastfeeding, and long use can cause dependence and electrolyte loss.
The plant is grown in gardens for the architectural foliage and for the flower spike, and it is used at the back of a border or beside water. The young stalks of some forms are eaten, but the ornamental species is not a reliable culinary plant, and the leaf should never be eaten.
Growing from Seed
Seed should be sown fresh in autumn or stratified for a month. Sow on the surface of a moist mix, cover lightly, and keep it cool; germination is in two to four weeks. The plant can also be divided in spring, which is the way to keep a selected form.
The plant wants deep, moist, rich soil and full sun, and it tolerates cold to about minus twenty. It needs room, since the leaves are a metre across, and it should be sheltered from strong wind, which shreds them. Water it in dry spells, mulch in autumn, and cut the flower spike if the foliage is the point.
Our Take
A bold foliage plant for a big border or a damp corner, and a medicine that belongs in a formula rather than in a salad.
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