The large, triangular leaves contain high levels of oxalic acid and anthrone glycosides, making them inedible.

By the early 18th century, these two species and a possible hybrid of unknown origin, R. × hybridum, were grown as vegetable crops in England and Scandinavia.

They readily hybridize, and culinary rhubarb was developed by selecting open-pollinated seed, so its precise origin is almost impossible to determine.

[5] The leaf stalks can be used raw while they have a crisp texture, but are most commonly cooked with sugar and used in pies, crumbles, and other desserts.

[8] The specific epithet rhaponticum, applying to one of the presumed parents of the cultivated plant, means 'rha from the region of the Black Sea'[8] or the river Volga, Rha being its ancient name.

In the United Kingdom, the first rhubarb of the year is harvested by candlelight in forcing sheds where all other light is excluded, a practice that produces a sweeter, more tender stalk.

Rhubarb damaged by severe cold should not be eaten, as it may be high in oxalic acid, which migrates from the leaves and can cause illness.

[20] Though Dioscurides' description of ρηον or ρά indicates that a medicinal root brought to Greece from beyond the Bosphorus may have been rhubarb, commerce in the plant did not become securely established until Islamic times.

During Islamic times, it was imported along the Silk Road, reaching Europe in the 14th century through the ports of Aleppo and Smyrna, where it became known as "Turkish rhubarb".

The merchant explorer Marco Polo therefore searched for the place where the plant was grown and harvested, discovering that it was cultivated in the mountains of Tangut province.

[24] The local availability of the plants grown for medicinal purposes, together with the increasing abundance and decreasing price of sugar in the 18th century, galvanised its culinary adoption.

[24] Rhubarb was harvested in Scotland from at least 1786, having been introduced to the Botanical Garden in Edinburgh by the traveller Bruce of Kinnaird in 1774.

"[29] The advocate of organic gardening Lawrence D. Hills listed his favourite rhubarb varieties for flavour as 'Hawke's Champagne', 'Victoria', 'Timperley Early', and 'Early Albert', also recommending 'Gaskin's Perpetual' for having the lowest level of oxalic acid, allowing it to be harvested over a much longer period of the growing season without developing excessive sourness.

In 2021–2022 this was moved from southern England to the more northern garden RHS Bridgewater where winter cold and rainfall are better suited for rhubarb.

[31] The following cultivars have gained the Royal Horticultural Society's Award of Garden Merit:[32] Rhubarb is grown primarily for its fleshy leafstalks, technically known as petioles.

[39] In Northern Europe and North America, the stalks are commonly cut into pieces and stewed with added sugar until soft.

[47][48][49] The toxic rhubarb leaves have been used in flavouring extracts, after the oxalic acid is removed by treatment with precipitated chalk (i.e., calcium carbonate).

The LD50 (median lethal dose) for pure oxalic acid in rats is about 375 mg/kg body weight,[50] or about 25 grams for a 65-kilogram (143 lb) human.

[56] Both fatal and non-fatal cases of rhubarb poisoning may be caused not by oxalates, but rather by toxic anthraquinone glycosides.

[58] Hungry wildlife may dig up and eat rhubarb roots in the spring, as stored starches are turned to sugars for new foliage growth.