Pelargonium acetosum (sorrel-leaved pelargonium)

Native to the south-eastern Cape in South Africa, with isolated localities near Uitenhage and in Orange Free State.

Pelargonium acetosum is a glaucous, succulent, much-branched shrub up to 60 cm tall and wide. Its irregularly lobed leaves are smooth, fleshy, greyish-green with red margins and borne on slender branches. When crushed, the leaf smells and tastes acidic, like common sorrel (Rumex acetosa). Its five-petalled flowers are 5 cm across, usually salmon-pink but also in paler shades, and borne throughout much of the year on long stiff stems.

Hand-coloured engraving of Pelargonium acetosum by James Sowerby (1790), taken from Curtis's Botanical Magazine (Image: RBG Kew)

Curtis’s Botanical Magazine (Editor: Martyn Rix) provides an international forum of particular interest to botanists and horticulturists, plant ecologists and those with a special interest in botanical illustration.

Now well over two hundred years old, the Magazine is the longest running botanical periodical featuring colour illustrations of plants. Each four-part volume contains 24 plant portraits reproduced from watercolour originals by leading international botanical artists. Detailed but accessible articles combine horticultural and botanical information, history, conservation and economic uses of the plants described.

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Though this species is common in many areas of the south-eastern Cape, it is vulnerable to grazing by goats.

Sorrel-leaved pelargonium is grown as an ornamental. The buds and young leaves are eaten in South Africa. They have a bitter taste but can be eaten raw in salads or added to soups and stews.

The Millennium Seed Bank partnership aims to save plant life worldwide, focusing on plants under threat and those of most use in the future. Seeds are dried, packaged and stored at a sub-zero temperature in Kew's seed bank vault at Wakehurst.

Description of seeds: Average 1,000 seed weight = 7.31 g.
Number of seed collections stored in the Millennium Seed Bank: One.
Seed storage behaviour: Orthodox (seeds of this plant survive drying without significant reduction in their viability and are therefore amenable to long-term frozen storage such as at the MSB)
Germination testing: 90% germination on 1% agar at 20°C, on a cycle of 8 hours daylight / 16 hours darkness. The pre-sowing treatment included seed scarification (chipping with scalpel).

Pelargonium acetosum is grown in sandy soil. It should be kept dry, especially in winter, and free from frost. It roots easily from cuttings.

In 1789, William Aiton listed 102 species of Pelargonium in his book Hortus Kewensis (a publication listing all species being grown at the Royal Botanic Gardens, Kew at the time), and the genus subsequently became incredibly popular amongst British gardeners.

Sorrel-leaved pelargonium is growing in the Princess of Wales Conservatory in the dry climate section.

Pressed and dried specimens of Pelargonium acetosum are held in Kew’s Herbarium, where they are available to researchers from around the world, by appointment. The details of some of these, including images, can be seen online in the Herbarium Catalogue.

Search Kew's databases for more information on this species

The British Pelargonium and Geranium Society

SEPASAL (Survey of Economic Plants for Arid and Semi-Arid Lands)

JSTOR Plant Science (includes images of Pelargoinum acetosum)

PlantzAfrica – Pelargonium acetosum

Curtis’s Botanical Magazine (Wiley-Blackwell)