Pelargonium leucopetalum E.M.Marais, 2024

Pelargonium leucopetalum E.M.Marais , sp. nov. ( Fig. 3 View FIGURE 3 )

Diagnosis:— Similar to P. pinnatum and P. reflexum (Andrews) Persoon (1806: 227) because all of them have spathulate petals and very short stamens concealed in the floral sheath. All three of them have white flowers, although in P. pinnatum a variation of pink and yellow flowers also occurs. They differ in that P. leucopetalum has prominent dark red blotches on the anterior petals, a characteristic lacking in the other two species. Pelargonium leucopetalum has upright pinnately divided leaves, trullate in outline, pinnae irregular in outline and very thin petioles, P. pinnatum has also upright pinnately divided leaves but narrowly oblong in outline with pinnae regular in outline and P. reflexum has prostrate trifoliolate leaves.

Type:— SOUTH AFRICA. Western Cape: 15 km from Redelinghuys on road to Aurora, near Tiernesberg , (3218 DA), 30 August 1987, E. M. Marais 309 (holotype NBG!; isotype K!)

A deciduous geophyte 150–300 mm tall when in flower. Tuber : turnip-shaped, elongated or moniliform root, covered with flaking dark brown periderms, 15–20 mm long and 8–15 mm in diam. Leaves: radical, erect, pinnately compound, petiolate; lamina simple (juvenile leaves), pinnate to bipinnate, trullate in outline, 45–70 mm long, pinnae sometimes regularly incised, 20–70 mm long, segments 1–3 mm wide, apices acute, adaxially and abaxially hirsute with appressed stiff hairs; petiole rigid, erect, 40–180 mm long, ± 1 mm in diam., brownish green, densely hirsute with appressed non-glandular hairs interspersed with short glandular hairs; stipules subulate, 7–20 mm long, ciliate, adnate to petiole, apices free. Inflorescence: scape (45–)90–200(–250) mm long, dark reddish green, densely hirsute with short appressed hairs interspersed with short glandular hairs, branched, bearing 2–3 pseudo-umbellets with 2–6 flowers each; peduncles 40–80 mm long, 1 mm in diam., pale reddish green, densely covered with appressed curly hairs interspersed with short glandular hairs with large glandular heads; bracts subulate, 3–5 mm long, abaxially covered with appressed hairs interspersed with short glandular hairs, margins ciliate; flower buds, flowers and fruits erect. Pedicel ± 0.5 mm long. Hypanthium 15–22 mm long, 1.5–2.0 times the length of the sepals, pale green to reddish green, densely covered with appressed curly hairs, interspersed with glandular hairs. Sepals 5, posterior one erect, others patent, linear-lanceolate, apices acute, 6.5–12.0 × 1.5–3.0 mm, reddish green in centre with green membranous margins, abaxially densely covered with glandular hairs and short appressed non-glandular hairs. Petals 5, white, spathulate, patent during anthesis, claws forming a sheath of ± 13 mm long, apices curved backwards, posterior two with wine red feather-like markings, 17–27 × 3.0– 7.5 mm, length/width ratio 3.5–6.8, claws 12–13 mm long, apices rounded; anterior three usually with prominent wine-red blotches, 16–27 × 1.8–4.0 mm, apices rounded. Stamens 10, basally connate, staminal column ± 1 mm long, smooth, white; fertile stamens 5, concealed in the floral sheath, posterior filament 1.5–2.0 mm long, lateral two filaments 2.0– 3.2 mm long, anterior two filaments 3–5 mm long, apices of free filaments white, 0.8 times the length of the sepals; staminodes ± 2 mm long; anthers wine-red, 1.2–1.4 mm long, pollen orange. Gynoecium: ovary 1.5–2.5 mm long; style 0.5–0.8 mm long; stigma with 5 recurved branches, 0.5–0.8 mm long, dark red. Fruit: bases of mericarps 5.0– 5.5 mm long, without glandular hairs, tails 20 mm long. Chromosome number: unknown.

Flowering period:— During late summer, from December to April.

Habitat:— Plants occur in fynbos usually under bushes on soil derived from sandstone, but were also collected on shale bands in areas with an annual precipitation of 300–400 mm during winter months. Populations usually consist of a few plants, although some records describe the species as locally common.

Distribution:— Along the west coast of the Western Cape Province, from Paleisheuwel and Aurora in the west and more inland to Pakhuis Pass and Nardous Pass in the east ( Fig. 4 View FIGURE 4 ).

Diagnostic characters:— Pelargonium leucopetalum has white flowers with feather-like markings on the posterior two petals and prominent dark red blotches on the anterior three petals, a characteristic rather unusual for flowers of sect. Hoarea , and pinnately divided leaves, trullate in outline, and very thin petioles. The spathulate petals and the very short fertile stamens are similar to those of P. pinnatum ( Marais, 1994) . About thirty other species of sect. Hoarea are also known for the very short stamens concealed in the floral sheath, of which P. reflexum and P. violiflorum (Sweet) Candolle (1824: 652) have white flowers with spathulate petals. The flowers of P. reflexum (posterior petals 10–18 mm long) are smaller than those of P. leucopetalum (posterior petals 17–27 mm long) and both species have wine-red feather-like markings on the posterior two petals. Pelargonium violiflorum has small flowers (posterior petals 7–12 mm long) without markings on the posterior petals. Both P. reflexum and P. violiflorum lack the prominent dark blotches on the anterior petals as in P. leucopetalum .

Conservation status:— With an increase in agricultural activities along the west coast of the Western Cape Province this species may become under threat. However, more in depth exploration is needed for the correct assessment of the extinction risk of this species. Therefore, according to IUCN (2024) guidelines, it is previously indicated as Data Deficient (DD).

Etymology:— The specific epithet refers to the white petals of the species (Latin leuco, white).

Notes:— The pinnately compound leaves, trullate in outline of P. leucopetalum resemble those of P. fumariifolium (yellow flowers), P. leptum L. Bolus (1932: 229 , 232), P. undulatum (Andrews) Persoon (1806: 226) and P. violiflorum (white flowers). The indumentum on the laminae and petioles of these five species is very similar. In all of them the laminae are hirsute with long appressed stiff hairs ( Marais, 1994). In P. fumariifolium the stiff hairs are interspersed with short glandular hairs and in P. undulatum and P. violiflorum the adaxial sides are usually glabrous. The petioles of all of them are hirsute with appressed hairs, usually shorter than those on the laminae and in P. undulatum , P. violiflorum and P. leucopetalum these hairs are interspersed with short glandular hairs. On the petioles of P. fumariifolium and P. leptum the glandular hairs are lacking.

Additional specimens examined:— SOUTH AFRICA, Western Cape: Nardous Pass, near farm Brakvlei , (3118 DD), 17 September 1988, E. M. Marais 324 ( STEU) ; Farm Grasberg, Nieuwoudtville , (3119 AC), 20 April 1979, B-E. Van Wyk 68 ( STEU) ; Bobergvlei, 23 km from Piekenierskloof on road to Paleisheuwel (3218 BD), 29 August 1987, E. M. Marais 307a ( STEU) ; 12 km N of Aurora (3218 CB), 27 January 1991, F. Albers 2502 ( STEU) ; Bakenskop, north western end of Piketberg range (3218 DA), February 1978, L. Hugo 1004 ( NBG) ; Piketberg, sandy flats at the dam below Levant Hill (3218 DC), December 1963, R. B. Nordenstam 3365 ( NBG, S) ; Pakhuis Pass (3219 AA), February 1941, C. J. Leipoldt 3794 ( BOL) ; February 1933, C. J. Leipoldt 20515 ( BOL) ; 20 September 1986, E. M. Marais 269 ( STEU) ; 2 July 1991, E. M. Marais 397 ( STEU) ; Pakhuis Pass, 20 km from Clanwilliam (3219 AA), 2 April 1986, E. M. Marais 194 ( STEU), 9 August 1986, E. M. Marais 206 ( STEU) ; Northern Cederberge, Kliphuis Forrest Station (3219 AA), February 1984, H. C. Taylor 10914 ( PRE) .