PlantLife Volume 60.7, December 2025. The Portulaca Project

The Portulaca Project

Text by W.R. Woodenberg and S. Ramdhani

Photos as indicated

Introduction

The plant genus Portulaca is a fascinating yet under-researched group of succulent herbs, characterised by their leaf axil hairs and fruit capsules that split horizontally (Fig. 1). As the only genus left in the Portulacaceae family after a recent DNA study (Nyffeler and Eggli 2010), Portulaca has a significant role in the plant kingdom as the bearer of a unique evolutionary lineage. These plants are adapted to thrive in disturbed areas with poor soil and direct sunlight (Ocampo and Columbus 2012), making them pioneers in ecosystem recovery and stabilisation. Some species, such as Portulaca oleracea (commonly known as purslane; Fig. 2), which you can find growing in disturbed areas (pavements included!), are edible and highly nutritious (Wright 2012). They are rich in omega-3 fatty acids (which we usually get from fish in our diet) and antioxidants and have been used in traditional medicine for their purported health benefits, including anti-inflammatory and anti-cancer properties (Ocampo and Columbus 2012).Many gardeners will also be familiar with species like P. grandiflora (Fig. 3) and P. umbraticola, which are popular ornamentals, valued for their vibrant flowers and ease of growing.

The ability of Portulaca to perform C₄ photosynthesis, a trait rare among succulent plants, allows them to use water efficiently and thrive in arid environments, making them ideal for xeriscaping (landscaping that reduces or eliminates the need for irrigation) and sustainable gardening practices (Voznesenskaya et al. 2010).

Despite its widespread distribution, particularly in tropical and subtropical regions of the world, this genus has been overlooked historically in terms of scientific study, especially in southern Africa. The last comprehensive taxonomic review in the region was conducted over 160 years ago (Sonder 1862).

Recognising this gap, a research project entitled ‘A revision of the Portulaca of southern Africa’ (aka the Portulaca Project) was launched in 2021 at the South African National Biodiversity Institute (SANBI). The research was conducted by Wynston Woodenberg (KwaZulu-Natal Herbarium) in collaboration with Syd Ramdhani (University of KwaZulu-Natal), with the project being part of a broader strategy to enhance our knowledge of plant biodiversity and address gaps in taxonomic information that are crucial for conservation efforts.

Figure 1: Portulaca obtusa showing axillary hairs (black arrow) and circumscissile fruit capsule (grey arrow) typical of Portulaca species. Photo: Wynston Woodenberg

Figure 2: Portulaca oleracea (purslane) growing along a pavement. Photo: Wynston Woodenberg

Figure 3: Portulaca grandiflora used as a groundcover at Durban Botanic Gardens. Photo: Wynston Woodenberg

Method

The Portulaca Project set out to explore the diversity of this genus across various regions in South Africa. Researchers consulted herbarium specimens from three SANBI herbaria and others, and collected additional specimens (Fig. 4) from several provinces including Mpumalanga, Limpopo and KwaZulu-Natal, to document the morphological characteristics and distribution patterns of each species.

 

Figure 4: Syd Ramdhani (left) and Wynston Woodenberg (right) collecting Portulaca specimens for the study in Postmasburg, Northern Cape. Photo: Yanadayalan (Teddy) Govender

Key findings

Species diversity: The study identified a total of ten Portulaca species in southern Africa – many more than the three listed in Sonder’s (1862) study. The species found in southern Africa are Portulaca grandiflora, P. hereroensis, P. kermesina, P. obtusa, P. oleracea, P. pilosa, P. quadrifida, P. trianthemoides, P. waterbergensis, and P. wightiana (formerly P. collina). While P. hereroensis, P. kermesina, P. pilosa, P. quadrifida, P. trianthemoides, P. waterbergensis, and P. wightiana are considered to be native to the region, P. grandiflora, P. obtusa, and P. oleracea are considered to be introduced. These species are either annuals (e.g. P. hereroensis and P. pilosa) or short-lived perennials (like P. kermesina and P. oleracea). They exhibit a variety of growth forms, from prostrate or mat-forming species like P. oleracea and P. quadrifida respectively, to erect species such as P. kermesina and P. trianthemoides. Notably, P. wightiana possesses specialised leaf axil hairs, which grow densely and have broad bases, seemingly to reflect the sun’s harmful rays in the arid regions where this species thrives.

One of the highlights of the study, however, was the rediscovery of Portulaca trianthemoides after 89 years. This species was last collected in 1934 in Soutpansberg, Limpopo. After some investigation and loads of luck, a healthy population was discovered near a saltpan in the area, allowing the capture of some of the first-ever photographs of live plants of this species.

Morphological characteristics: Based on analyses of the findings of the Portulaca Project, here is a simple guide to distinguish the species found in southern Africa: If the leaves are thin and round (linear-terete), start with their growth habit. Erect plants with red/magenta, elliptic petals are Portulaca kermesina (Fig. 5A). If the plant sprawls on the ground and has magenta, obovate petals, check the stems. Hairless stems with large (15–40 mm) flowers and a red petal base indicate P. grandiflora (Fig. 5B), while hairy stems with smaller (<14 mm) flowers and a white petal base point to P. pilosa (Fig. 5C). If the leaves are broader (planar), note their arrangement. Alternate leaves with more than four petals lead to P. obtusa (pink petals with yellow bases; Fig. 5D), P. trianthemoides (erect growth form, narrowly oblanceolate leaves, and yellow flowers; Fig. 5E), or P. oleracea (prostrate growth form, broadly obovate leaves, and small yellow flowers; Fig. 5F). Opposite leaves usually mean four-petaled flowers — yellow ones could be P. quadrifida (thin axillary hairs; Fig. 5G) or P. wightiana (hairs with flattened, broad bases; Fig. 5H). If they have white petals, the lilac anthers, tuberous roots and see-through underside of leaves mean P. waterbergensis (Fig. 5I), while white anthers and non-tuberous roots with green-glaucous leaves indicate P. hereroensis (Fig. 5J).

 

Figure 5: A. Portulaca kermesina; B. Portulaca grandiflora; C. Portulaca pilosa; D. Portulaca obtusa; E. Portulaca trianthemoides; F. Portulaca oleracea; G. Portulaca quadrifida; H. Portulaca wightiana; I. Portulaca hereroensis; and J. Portulaca waterbergensis. Photos: A–D; F–I Wynston Woodenberg; E. Rangani Nemando; J. Ben Willemse

Ecological Roles: Portulaca species play vital roles in their ecosystems in southern Africa. They are often found in rocky or shallow soils where few other plants can survive (e.g. the recently described Portulaca waterbergensis [Peckover 2021]), thus contributing to soil stabilization and providing habitat for other organisms. Their flowers attract a variety of pollinators, including bees, that are essential for the health of natural ecosystems.

Distribution: The Limpopo province of South Africa boasts the highest diversity of Portulaca in the Flora of Southern Africa region, hosting all ten species. Portulaca oleracea is the most widespread, ranging from Namibia and Botswana to every province in South Africa. Portulaca quadrifida follows closely, occurring throughout the region except in Lesotho. Other species, like P. hereroensis and P. kermesina, have more restricted inland distributions, while P. grandiflora thrives near major cities, likely due to its being a garden escapee. Gauteng is a hotspot for P. obtusa, that may have arrived via trade with Argentina. Meanwhile, P. wightiana prefers dry regions, P. pilosa is confined to the northeast, and P. trianthemoides and P. waterbergensis are endemics found only in Limpopo’s Soutpansberg and Waterberg regions, respectively.

 

Challenges in Taxonomy

Despite the progress made by the Portulaca Project, the taxonomy of Portulaca remains challenging. Several species are morphologically similar, making it difficult to distinguish them without detailed examination of specific characteristics such as leaf shape, flower structure and seed morphology.

 

For example, Portulaca obtusa has been frequently misidentified as the pink-flowered form of P. quadrifida in southern Africa. However, closer inspection by the Portulaca Project revealed distinct differences: P. obtusa has pink petals with a pale-yellow base and erect stems, whereas P. quadrifida has plain yellow petals and a prostrate growth habit. These subtle yet crucial distinctions are vital for accurate species identification and classification.

 

The way forward

The work undertaken in the Portulaca Project is a significant step toward filling the knowledge gaps in the taxonomy of this important genus. However, more research is needed to fully understand the diversity and ecological roles of Portulaca species in southern Africa. Future studies should focus on molecular analyses to complement morphological data, providing a more comprehensive understanding of the evolutionary relationships within the genus.

In addition, there is a need for increased public awareness and appreciation of these often-overlooked plants. By highlighting their ecological, economic, and medicinal value, we can foster greater interest in their conservation. Community-based initiatives that promote the use of Portulaca species in sustainable landscaping and traditional medicine can also contribute to this goal.

 

Conclusion

The Portulaca Project has shed new light on a group of plants that are as fascinating as they are diverse. By revisiting this neglected genus, we are reminded of the importance of every plant species in maintaining the balance of our ecosystems. As we continue to explore and understand the natural world, initiatives like the Portulaca Project are crucial for conserving our region’s rich biodiversity and ensuring that all species, no matter how small or seemingly insignificant, are given the attention they deserve.

If you’re interested in learning more about the study, results will be published soon in the South African Journal of Botany.

 

Acknowledgements

We wish to thank SANBI and the Botanical Education Trust for funding.

 

References

NYFFELER, R., EGGLI, U., (2010). Disintegrating Portulacaceae: a new familial classification of the suborder Portulacineae (Caryophyllales) based on molecular and morphological data. Taxon 59: 227–240.

OCAMPO, G., COLUMBUS, J.T., (2012). Molecular phylogenetics, historical biogeography, and chromosome number evolution of Portulaca (Portulacaceae). Molecular Phylogenetics and Evolution 63: 97–112.

PECKOVER, R., (2021). Portulaca waterbergensis (Portulacaceae), an unusual new species from the Waterberg, Limpopo Province, South Africa. CactusWorld 39: 327–330.

SONDER, O.W., (1862). Portulacaceae. Flora Capensis 2: 381–386.

VOZNESENSKAYA, E.V., KOTEYEVA, N.K., EDWARDS, G.E., OCAMPO, G., (2010). Revealing diversity in structural and biochemical forms of C₄ photosynthesis and a C₃–C₄ intermediate in genus Portulaca L. (Portulacaceae). Journal of Experimental Botany 61: 3647–3662.

WRIGHT, C.A., (2012). Purslane. Mediterranean vegetables: a cook’s compendium of all the vegetables from the world’s healthiest cuisine, with more than 200 recipes. Harvard Common Press. Boston, Massachusetts.