Kalanchoe × robertsonii Gideon F.Sm., 2022

Smith, Gideon F., 2022, Kalanchoe × robertsonii [K. longiflora × K. rotundifolia] (Crassulaceae subfam. Kalanchooideae), a new, small-growing nothospecies from South Africa, Phytotaxa 561 (1), pp. 85-94 : 90-91

Kalanchoe × robertsonii Gideon F.Sm. nothospec. nov. ( Fig. 2A–E ).

Type:— SOUTH AFRICA. Gauteng province —2528 (Pretoria): Tshwane , (– CA), ex hort., 25 April 2022, G. F. Smith 1180 (holotype PRU) .

Parentage:— Kalanchoe longiflora Schltr. ex Wood (1903 : t. 320) × K. rotundifolia ( Haworth 1824: 188) Haworth (1825: 31) .

Diagnosis:— Kalanchoe × robertsonii is a low-growing leaf succulent that in both vegetative and reproductive morphological characters is generally intermediate between its parents, K. longiflora and K. rotundifolia . However, leaves of K. × robertsonii are narrowly oblong to obovate rather than obovate to nearly orbicular as in K. longiflora or oblong-elliptic to elliptic-obovate as in K. rotundifolia . As in K. rotundifolia , the inflorescence of K. × robertsonii is a corymbose cyme, while that of K. longiflora is a thyrse. Kalanchoe × robertsonii has flowers that are gradually urnshaped above the ovary, but less so than in K. longiflora , while those of K. rotundifolia are abruptly urn-shaped above the ovary. Corolla tubes of K. × robertsonii are shiny greenish yellow, while those of K. rotundifolia are reddish orange and strongly green-infused proximally; those of K. × robertsonii are shiny light orange and lightly green-infused in the lower half. The colour of the adaxial surfaces of the corolla lobes of K. longiflora is monochromatic light yellow, that of K. rotundifolia is generally monochromatic red to dull orange, while that of K. × robertsonii is bicoloured, being dull to bright light orange distally and strongly yellow-infused proximally.

Description:—Perennial, few- to many-leaved, sparsely branched from the base, glabrous, dull light green to glaucous, with light waxy bloom, small, low-growing succulent, with erect to leaning stems (0.25–)0.30–0.45(–0.50) m long when in flower. Stems few arising from fibrous rootstock, thin, erect to leaning, light glaucous green, strongly orange-infused to virtually orange throughout, simple at first, sometimes producing branchlets near the base, main stems with few branches higher up post-flowering, leafless lower down, especially at onset of dry season. Leaves (30–)45–60(–70) × (10–)14–18(–20) mm, glaucous to very light green, sometimes lightly or strongly orange-infused especially in dry season, with slight bloom, opposite-decussate, pseudo-rosulately clustered towards stem apices, very finely orange-dotted towards margins, generally sparsely arranged; petiole absent; blade succulent, narrowly oblong to obovate, flat, straight or slightly curved upwards; apex rounded, obtuse, blunt; base cuneate, gradually tapering towards stem; margin flat; entire for proximal ⅔–¾, usually with few rounded, harmless crenations towards leaf apex, often more intensely orange-infused. Inflorescence a corymbose cyme, (250–)270–300(–340) mm tall, with leaf-like bracts at nodes, floriferous only at the top, erect or leaning, apically sparsely branched, few- to many-flowered, rather round in outline when viewed from above, branches opposite, subtended by small, persistent leaf-like bracts, leafy branchlets not produced in axils, axis light glaucous green, strongly orange-infused to virtually orange throughout, with slight bloom; pedicels slender, 4–8 mm long, orange-infused. Flowers tetramerous, sometimes pentamerous, 15–16 mm long, erect; calyx light shiny green, strongly orange-infused, more intensely so distally, lacking a slight bloom; sepals 4, 2.5–3.0 × 1.0– 1.5 mm, separate, basally fused for about 1 mm, deltoid-elongated-triangular, acute, hardly contrasting against basal part of corolla, apically straight; corolla 14–15 mm long, enlarged basally around carpels, abruptly attached to pedicel, not distinctly and tightly anti-clockwise-twisted apically after anthesis; corolla tube 13–14 mm long, orange in bud, distally bright orange, greenish-infused around ovaries at anthesis, and basally at level of sepals, gradually becoming terete upwards above carpels, rounded-4-angled, gradually urceolate, somewhat box-shaped-square when viewed from below; lobes 4–5 × 3.5–4.0 mm, spreading at 90°-angle or slightly to distinctly recurved, bicoloured, dull to bright light orange distally, strongly yellow-infused proximally, ovate to very slightly elliptic; centrally shallowly furrowed, straight along margin, distinctly acute apically, minutely apiculate, not showing diurnal movement. Stamens inserted in two ranks just below and at middle of corolla tube, included but visible at mouth; filaments 2.0– 2.5 mm long, thin, yellow; anthers 0.75–1.00 mm long, dull yellow. Pistil consisting of 4 carpels; carpels 5–6 mm long, light green, strongly orange-infused; styles 2 mm long, yellowish green; stigmas whitish, prominently capitate; scales 2.00– 2.25 mm long, cylindrical to ribbon-like-linear, tapering upwards, light yellow. Follicles 7–8 mm long, light green, at first enveloped in dry, orange-brown, remains of corolla tube, often shedding dry corolla tube early on, then exposing still light green follicles, remains of corolla tube later turning whitish to brownish black, eventually brittle, grass spikelet-like, splitting star-like. Seed 0.4–0.5 mm long, brown to blackish brown, faintly striated, ellipsoid to somewhat banana-shaped-curved. Chromosome number: unknown.

Flowering time:— Kalanchoe ×robertsonii flowers mainly in the autumn and winter months, (March–)April to July(–August), in the southern hemisphere. However it has been observed as flowering out-of-season in late-spring and in early-summer.

Eponymy:— Kalanchoe × robertsonii is named for Prof. Dr Bruce Leonard Robertson (18 April 1944 [Pretoria, South Africa]–) ( Fig. 2F ) who, at the age of 17 enrolled at the University of Pretoria, graduating with an M.Sc. (Agriculture) for his study of the embryology of avocado [ Persea americana Miller (1768 : fifth page headed PER PER, page not numbered)] in 1969. In 1972 he joined the staff of the Department of Botany at the University of Port Elizabeth (U.P.E.), now the Nelson Mandela University, as a lecturer, where he obtained a Ph.D. in 1975 for his research on the distribution, seed germination, developmental anatomy, and embryology of the South African endemic palm, Jubaeopsis caffra Beccari (1914: 173) (see Wicht 1969: 35–37, Robertson 1976a, b, Jones 1995: 234–235, and Dransfield et al. 2008: 401–404).

Bruce subsequently completed a postdoctoral sabbatical at the University of Alberta in Edmonton, Canada, where he researched the ultrastructural embryology of barley [ Hordeum vulgare Linnaeus (1753: 84) ]. Thereafter he returned to U.P.E. where he progressed through the academic ranks to Professor of Botany in 1991. In 1998 he was appointed as Director of the Institute for Coastal Research of U.P.E. His research during this period focussed mainly on the reproduction, harvesting, and aquaculture of macroalgae, leading to him undertaking projects at Dalhousie University, Halifax, Canada, as well as at the Marine Research Station in Tainan, Taiwan. His research programme produced a large number of research publications, and Master’s and Doctoral students. He was appointed Head of U.P.E.’s Department of Botany in 1998, and in 1999 he was appointed as the University’s first Director of Research.

Professor Robertson occupied this post until his retirement in December 2004. As an emeritus Professor, he has continued to undertake contractual projects relating to research management and post-graduate student mentoring in a number of the University’s faculties. Professor Robertson served on and chaired numerous professional Boards and Councils, for example of the South African Association of Botanists, Phycological Society of South Africa, South African Council of Natural Scientists, South African Network for Oceanographic Research, and as the Senate Representative on the Council of the University of Port Elizabeth (2002–2004).

The naming of K. × robertsonii for Prof. Robertson celebrates his 78 th birthday on 18 April 2022 and recognises his many and varied contributions to plant sciences in South Africa, and beyond.

Figures

FIGURE 2. Kalanchoe ×robertsonii. A. Leaves and stems. At first the leaves are light green to glaucous, later becoming orange-infused, especially towards the leaf margins. The margins are flat and entire for the proximal ⅔–¾, usually with few crenations towards the leaf apex. B. The adaxial surface of the ovate to very slightly elliptic corolla lobes of K. ×robertsonii is bicoloured, i.e., dull to bright light orange distally and strongly yellow-infused proximally. C. Corolla tubes of the nothospecies are shiny light orange and only lightly greeninfused in the lower ½ (flower in the centre), while those of K. longiflora are uniformly shiny greenish yellow (flower on the left) and those of K. rotundifolia are red to dull orange and often strongly green-infused proximally (flower on the right). D. The adaxial surface of the corolla lobes of the nothospecies is dull to bright light orange and strongly yellow-infused (flower in the centre), while that of K. longiflora is monochromatic light yellow (flower on the left) and that of K. rotundifolia is monochromatic red to dull orange (flower on the right). E. The aberrant flower of K. ×robertsonii in the centre is pentamerous, rather than tetramerous as in the case of all Kalanchoe species. Such a deviation in the number of flower parts is often found in interspecific Kalanchoe hybrids. F. Prof. Dr Bruce Leonard Robertson (1944–) after whom K. ×robertsonii is named; photograph taken on 26 May 2019. All photographs: Gideon F. Smith.