Common Houseplant Cleans the Air in South Africa

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Some people feel the elephant bush (Portulcaria afra), commonly grown as a houseplant elsewhere, may become the climate change saviour of South Africa. Photo: youngsgardenshop.com

Do you know what a spekboom is? Unless you live in the Republic of South Africa, probably not, because it’s the common Afrikaans name there for a native shrub that, in other countries, is more likely to be grown as a houseplant. You might instead know it under the name elephant bush* or dwarf jade (Portulcaria afra). (The name spekboom actually means fat tree or bacon tree.) And there’s a huge campaign underway in South Africa to plant more spekbooms for environmental purposes.

*For simplicity’s sake, in this article I’ll call this plant by its South African name, spekboom.

The #spekboomchallenge was launched in 2018 by the Nels family of Boplass Farm in Calitzdorp, Western Cape, South Africa. They vowed to plant one million spekbooms by 2025 and challenged other South Africans to join them. The idea is that the spekboom is particularly efficient at sequestrating carbon, the claim being that a single bush is able to remove 100 times more carbon dioxide from the air than a full-grown pine tree. Hectare for hectare, spekboom thicket is even said to be as effective as the Amazon rainforest at removing carbon dioxide from the atmosphere. That’s undoubtedly an exaggeration, but, considering that most succulents are less efficient at storing carbon than other plants, and the spekboom, which carries out two forms of photosynthesis, almost doubling its efficiency at CO2 absorption, is verifiably very good at it, this is a surprising and important finding.

People across South Africa are joining together to plant spekbooms. Photo: http://www.capetownetc.com

With an entire nation planting spekbooms (many municipalities, companies, associations and just plain home gardeners have joined the challenge), it is hoped that this will considerately reduce South Africa’s carbon footprint. Some sources even claim it may even make a serious dent in climate change throughout the entire southern third of the African continent. That’s certainly an exaggeration, but even so, regreening pavement, asphalt and other barren spaces is certainly a step in the right direction.

The #spekboomchallenge now reaches well beyond South Africa, though. In Great Britain,  The Spekboom Project was launched recently with the aim of removing half a million metric tons of CO2 from the atmosphere by persuading millions of British people to keep one as a houseplant. And other projects are under study elsewhere around the world.

In South Africa

In the tree’s native land, Spekbooms are being planted in public gardens, at schools, along city streets, in private gardens and even in pots on balconies and decks. Since it can be maintained as modestly sized shrub (although, left on its own, it will eventually form a small tree up to 5 m tall), it needn’t take up much space. It can easily be trimmed into a hedge or even used for topiary.

The spekboom is a tough and easy-to-grow plant, tolerating both extreme heat and considerable cold (down to just about -2° C/30° F, although it does best where temperatures remain above 4° C/40° F at all times). It easily adapts to poor soils, irregular rainfall and extended periods of drought. As a result, it can be grown pretty much anywhere in South Africa except on the highest mountains.

It’s also fire resistant and even edible, with a sweet/sour taste. Leaves are commonly used in salads, notably.

Bringing Back the Spekboom Forest

Vast areas of South Africa were once covered with spekboom trees. Photo: ispotnature.org

Before spekboom forests, called subtropical thicket, were felled to make way for livestock farming some 200 years ago, they covered millions of hectares in the Eastern Cape region of South Africa. The forests were so thick it was said that a grown human could walk across the top as if walking on a carpet! 

African elephant munching on spekboom. Photo: ezethutours.co.za

The spekboom is a favorite fodder of elephants, black rhinoceros, kudus and many other South African animals. In fact, the common name “elephant bush” derives from the African elephant’s love for the tree. Elephants and other browsers are also the main propagators of the plant in the wild: as they eat, they break off branches and crush them to the ground … where they root and produce new spekboom plants. 

The sprawling spekboom thickets of yesteryear are now long gone … but there’s no reason they couldn’t be reconstituted and the #speekboomchallenge is helping to ensure they will be. In fact, spekbooms are increasingly used for landscape restoration projects throughout the region. For example, the South African government’s Working for Ecosystems program proposes restoring a million hectares (2.5 million acres) of spekboom thicket.

Spekboom as a Houseplant

This low-growing, weeping variety, commonly sold as the species, is actually Portulacaria afra ‘Prostrata’, a creeping selection. Photo: revivalnursery.myshopify.com

Guess what? You can grow this plant as a houseplant even if you don’t live in South Africa: yes, right in your own living room! Or even outdoors if you live in a frost-free climate (USDA zones 10–11). It’s not even a rare plant: most garden centers carry it. Look for it in the cactus and succulent section. Again, you’re more likely to find it labeled elephant bush or dwarf jade than spekboom … and the botanical name, Portulacaria afra, will confirm its identification.

The plant was long included in the Portulacaceae family, as indeed its Latin name suggests, but was recently transferred to the Didiereaceae family.

Spekboom leaves look much like jade leaves, but are much smaller… and the stems are reddish. Photo: http://www.ecoman.co.za

Look for a succulent plant with a thick reddish-brown stem, usually multiple branches and with thick spoon-shaped opposite leaves much like those of the jade plant (Crassula ovata), only several sizes smaller (1.25-2 cm/½-¾ in), often leading to confusion, although the jade plant is not even a close relative, belonging to the Crassulaceae family. The tiny pink to white flowers are rarely produced indoors.

Rainbow bush (Portulacaria afra ‘Variegata’) Photo: uhlig-kakteen.de

Often the variety sold is ‘Prostrata’ (although it is rarely labeled as such), with spreading stems, giving a groundcover to weeping effect. There are variegated cultivars too, all more upright growers, such as the very popular “rainbow bush” (P. afra ‘Variegata’), with green leaves edged in creamy white, or the rarer midstripe rainbow bush (P. afra ‘Medio-picta’), with a cream-colored stripe down the middle of the leaf. 

Give the plant bright light with at least some direct sun. Full sun is, in fact, best in most regions, although if your area is subject to very hot summers, you might want to move it back from the window at that time of year. It also thrives under grow lights. 

You can move it outdoors for the summer, gradually acclimatizing it to partial or even full sun. In climates where the sun is really intense, like in southern California, it should be protected from full midday sun. 

Carefully pruned, speekboom is sometimes used as an indoor bonsai. Photo: save-image.com

Water your spekboom like the succulent it is: thoroughly, but then letting it dry out well before watering again. In the summer, that can mean weekly watering, but in the winter, you can space out the waterings much more: perhaps every 10 to 14 days. In fact, if you can provide cool conditions (less than 10° C/50° F), you may not need to water it all winter.

The rest is a snap. Spekboom tolerates both dry and humid air, can be planted in any well-draining potting soil (houseplant mix, cactus and succulent mix, bonsai mix, etc.) and needs little fertilizer: only perhaps one quarter of the recommended rate and even then, only in spring or summer. Any fertilizer will do.

Stem cuttings root easily. Photo: WVC, desertification.wordpress.com

Spekboom is readily propagated from stem cuttings, best taken in spring or summer. Cut off a branch, remove the lowest leaves and let the cut end heal for a few days, then simply insert it into a pot of growing mix. Don’t water at first (this helps prevent rot), but when you see new growth appear all on its own, probably after 4 to 6 weeks, this is a sign it has rooted and you can start watering it normally.


Call your plant what you want: spekboom, elephant bush or dwarf jade (I call it portulacaria), but do consider growing this plant and spreading the #spekboomchallenge all over the world!

2 thoughts on “Common Houseplant Cleans the Air in South Africa

  1. How embarrassing! I could not find information about this species just recently, because I was looking for it as a species of Crassula. Oops. There is some right here as I type this. It is quite popular as a large potted plant for paved areas in Southern California.

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