Post #23 A new species of Pelargonium from Swartland

Fig. 1 (header): Flowers of the new taxon develop in few-flowered inflorescences and are similar to P. proliferum.

During the winter of 2019, while visiting some of the few remaining Swartland renosterveld patches with Riaan van der Walt, he pointed out a population of geophytic pelargoniums that looked like it could be different to anything else we had known by then, even when looking at the leaves only. These had recurved petioles, which could point at only a few possibilities, none of which seemed likely and many would be entirely out of place in Swartland.

Of these, P. ternifolium with ternate leaves and P. elandsmontanum with Oxalis-like leaves are indeed found in the general area, however, both have only two posterior petals and no anterior ones. The other taxa with recurved petioles such as P. montaguense, P. reflexum, P. fergusoniae, and P. nephrophyllum, as well as another as yet undescribed taxon from the vicinity of Kamieskroon, are of course found at a fair distance from Swartland.

It is unclear what advantage recurved petioles might bring to a plant, perhaps they make it more difficult for tuber-foraging animals, such as porcupines, to find their food. In any case, these are considered to be a key character of diagnostic value.

The flowers (Fig. 1) are remarkably similar to P. proliferum: short petals with feather-like markings on all five petals, as well as short nectar tubes (hypanthia). In fact, many observations of this taxon are currently identified as P. proliferum, for the simple reason that when they flower, the leaves are long gone.

The flowering time of this species is early autumn, i.e. March in the southern, or September in the northern hemisphere. This is also quite unlike any other species that could be mistaken for it. P. proliferum (as we currently understand this complex taxon with its many forms that could be described as separate taxa) typically flowers earlier, i.e. October to December [1].

The laminas are unusually glossy and thick, some are hairless, and some have long adpressed bristles at the margins and extremely short glandular hairs that appear only as small droplets under the microscope. This latter character is shared with P. pilosellifolium, which can be found growing nearby, at the southern foothills of the Piketberg range, but of course does not have recurved petioles such as our taxon (Fig. 2). At this particular location, P. pilosellifolium has pinnately divided leaves, a form that can be found throughout the Cederberg mountains – however, we will have to look at the three forms of P. pilosellifolium some other time.

Fig. 2: The typically recurved petioles of the new Swartland Hoarea.

The taxon must have been quite widespread before most of Swartland was ploughed over and converted into wheat fields. It can be found from the suburbs of Cape Town and Stellenbosch, all the way to Piketberg, often in quite dense colonies (Fig. 3). Some of these populations have entire to tripartite leaves, others have finely pinnate to bipinnate leaves, trullate (fan-shaped) in outline.

Fig. 3: A dense population with entire to broadly pinnate leaves. Populations with finely pinnate leaves are more frequent.

The typical habitat is Swartland renosterveld, where it can be found growing in some of the areas that are extremely popular with tourists looking for spring flowers (Fig. 4). Some of these areas are protected, although it is to be expected that once the taxon is described it will be considered as endangered if not red-listed.

Given that this taxon flowers in the autumn, it is not a surprise that it has not been noticed before. Many of the recent discoveries either have extremely small, localised populations, or flower at times that could be considered unusual for hoareas, such as in the middle of the summer or in the autumn, when few botanists venture into the veld.

Fig. 4: A riot of spring flowers in the renosterveld plains of the Swartland. The autumn looks very different; however, this is when our taxon flowers.

Given its late flowering time, when few other hoareas are in flower, the taxon is really worth growing and is without doubt unique. It probably requires slightly more water than other hoareas, as some of the habitats can be quite wet. Its Geraniaceae Reference Collection code is GER545.

By Matija Strlic, Ljubljana, Slovenia.

Literature

1. M. Marais (1994), Taxonomic studies in Pelargonium, section Hoarea (Geraniaceae). PhD Thesis, University of Stellenbosch.

Citation and Copyright

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ISSN 2464-014X.

This article was first published in Geraniaceae Group News #168. Cite as: M. Strlič: A new species of Pelargonium from Swartland. Geraniaceae Group News #150, pp 27-31.