P. grenvilleae, a member of the Incrassatum group of section Hoarea shares an easily recognisable and very typical character with its sister species, P. incrassatum, i.e. the s-shaped doubly-recurved nectar tubes (hypanthia). Both species have posterior petals significantly bigger than the anterior ones and while for most of its distribution the flowers of P. incrassatum are intensively pink or purple, the petals of P. grenvilleae are cream coloured. Only at the very northern end of the distribution of P. incrassatum, in the N Richtersveld, the petals are light pink or even white, however, never cream.
According to [1], the known distribution of P. grenvilleae is very limited indeed, particularly in comparison with P. incrassatum. Only a few herbarium specimens are available, mostly around Steinkopf, Springbok and Concordia, with further collections in the Hester Malan Wild Flower Reserve, the southernmost location being Rooiberg in the Kamiesberg Mountains. On the other hand, P. incrassatum has been frequently collected across the Namaqaland, from the N Richtersveld to close to Clanwilliam.
In September 2019, while looking for P. sp. nov. aff. caroli-henrici [2] with Florent Grenier, on a farm 15 km NE of Bitterfontein, 350 m a.s.l., and with kind permission by the farmer, we came across a small population of plants (Fig. 1) that did not look like any Hoarea taxon that would normally be expected here. The leaves were not hairy enough for P. moniliforme. The plants could be juvenile P. aristatum, which in the Knersvlakte has very broad pinnae, although the numerous leaves did not indicate a juvenile stage.
Fig. 1. P. grenvilleae, habitat photo, 15 km NE Bitterfontein.
Upon flowering (Fig. 2), the plants turned out to be P. grenvilleae. The unusual feature was the extremely high number of flowers per inflorescence, up to 64. In addition, the leaf shapes were unusual for this taxon, and the description of this species needs to be revised to include laminas that are longer than wide. The elongated laminas of Bitterfontein plants were 3-4 cm long and 1.5-2 cm wide. In all other characters, the plants fitted the currently valid description [1].
Fig. 2. Inflorescence of P. grenvilleae.
Fig. 3. Updated distribution of P. grenvilleae Andr. (Harv.)
Although this was a surprise, the nearby populations of P. incrassatum and P. confertum indicated that the area harboured several typical Namaqualand horaeas, in addition to those that are common in the Knersvlakte, such as P. leipoldtii, P. moniliforme or P. aristatum. A small population of P. sp. nov. aff. caroli-henrici [2] was also growing nearby. Due to intensive grazing, the population of P. grenvilleae should be considered as threatened.
The new location extends the known distribution of P. grenvilleae southwards by about 100 km, broadly overlapping with the distribution of P. incrassatum (Fig. 3). It is likely that P. grenvilleae is less frequently observed in the habitat as it is superficially similar to P. moniliforme, with which it could potentially be confused.
By Matija Strlic, Ljubljana, Slovenia.
Literature
- M. Marais: Taxonomic Studies in Pelargonium, Section Hoarea (Geraniaceae), Ph. D. Thesis. University of Stellenbosch, South Africa, 1994.
- Strlič: Pelargonium sp. nov. aff. caroli-henrici, The Pelargonium Page.
Citation and Copyright
© The Author. This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
ISSN 2464-014X.
This article was first published in Geraniaceae Group News #160. Cite as: M. Strlič: A Significant Extension of Known Distribution of Pelargonium grenvilleae Andr. (Harv.). Geraniaceae Group News #160 (2021), pp 21-24.