Pelargonium acetosum (sorrel-leaved pelargonium)
Originating in South Africa, the sorrel-leaved pelargonium is an elegant evergreen with a long flowering season that has been grown in England since 1724.
About this species
There are around 280 species of Pelargonium, over 200 of which are native to South Africa. These attractive plants have long been prized by gardeners, and some were brought to Europe at a surprisingly early date. Pelargonium acetosum, for example, was growing in the medicinal plant garden in Amsterdam by 1703 and in the Chelsea Physic Garden by 1724.
Originally described in 1753 as Geranium acetosum by the Swedish botanist and ‘father of taxonomy’ Carl Linnaeus, the name was changed to Pelargonium acetosum by the French botanist Charles Louis L'Héritier de Brutelle in 1789.
Unlike many other pelargoniums, this species does not have attractively scented leaves; acetosum (Latin = sour) refers to the acid taste of the leaves.
Geography & Distribution
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.
Illustration from Curtis's Botanical Magazine
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.
Published for the Royal Botanic Gardens, Kew by Wiley-Blackwell Publishing.
See the Wiley-Blackwell Subscription Information page for rates (for both print and online).
Threats & Conservation
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.
Millennium Seed Bank: Seed storage
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.
Pelargoniums at Kew
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.
This species at Kew
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.
JSTOR Plant Science (includes images of Pelargoinum acetosum)
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