Kalanchoe, Adanson, 1763

Smith, Gideon F. & Hankey, Andrew, 2021, Kalanchoe × forbesiae (Crassulaceae subfam. Kalanchooideae) derived from K. lubangensis × K. sexangularis: towards improved horticultural material, Phytotaxa 528 (5), pp. 290-300 : 295-298

Kalanchoe × forbesiae Gideon F.Sm. & Hankey, nothosp. nov. ( Figs 5 & 6 )

Type: — SOUTH AFRICA. Gauteng province —2528 (Pretoria): Pretoria, (– CA), ex hort., originating from the Walter Sisulu National Botanical Garden, South African National Biodiversity Institute , 27 September 2021, G . F . Smith 1162 (holotype PRU) .

Parentage: — Kalanchoe lubangensis Fernandes (1980: 400) × Kalanchoe sexangularis Brown (1913: 120) var. sexangularis .

Diagnosis: —Plants of Kalanchoe ×forbesiae differ from K. lubangensis , one of its parents, by being perennial through developing branches low down on the stem, as is often found in K. sexangularis , the other parent. In contrast, K. lubangensis is a biennial species. The leaves of K. × forbesiae are slightly smaller and rounder than those of K. sexangularis and weakly red-infused, with distinct red-infusion being a characteristic of the latter species. However, the venation of the leaves of K. × forbesiae is conspicuous abaxially, as found in K. lubangensis , but not in K. sexangularis . In reproductive characters, especially of the flowers, K. × forbesiae is similar to K. sexangularis , with the exception that the corolla tube is yellow to very faintly greenish infused, rather than often distinctly yellowish green.

Description: —Perennial, few-leaved, sparsely branched from base, glabrous succulent, ± 0.65 m tall. Stems light green to wine-red, few, erect to leaning under weight of inflorescence, with several lengthwise running ridges, 4-angled on sterile and fertile shoots, leafy branchlets produced in leaf axils lower down. Leaves opposite-decussate, petiolate, spreading or recurved, variously twisted from horizontal and vertical planes; petiole 8–10 mm long, channelled above, lower leaves not clasping stem, upper leaves nearly amplexicaul; blade 90–120 × 65–70 mm, light green infused with red especially towards margins, succulent, broadly elliptic or obovate to oblong, often folded lengthwise, ± straight, not recurved in upper half; base cuneate; apex rounded-obtuse; margins variously entire or coarsely crenate or undulatecrenate into rounded, harmless, crenations. Inflorescence ± 480 mm tall, erect to leaning, apically dense, manyflowered, flat-topped thyrse with several dichasia, branches opposite, curved upwards at an angle of 45°, subtended by small, leaf-like bracts; peduncle reddish-infused, with successively longer internodes upwards; pedicels 4–5 mm long, slender. Flowers erect in bud and at anthesis; calyx shiny light greenish yellow, not red-infused, same colour as and not contrasting against corolla tube; sepals 4, 1.5–2.0 × 0.75–1.00 mm, triangular-lanceolate, ± separate, succulent, basally adnate, acute-tipped; corolla 14–17 mm long, very slightly enlarged lower down, hardly tapering to mouth; tube 13–16 mm long, yellow to very faintly greenish-infused, distinctly 4-angled, box-shaped-square when viewed from below, very slightly longitudinally fluted above; lobes 4 × 3.5–4.0 mm, ovate to subcircular, rounded at apex, apiculate, light yellow. Stamens inserted well above middle of corolla tube, in two ranks, slightly exserted; filaments 3–5 mm long, thin, yellow; anthers 0.3–0.5 mm long, light brownish yellow. Pistil consisting of 4 carpels; carpels 6–8 mm long, light yellowish green; styles 4–5 mm long; stigmas very slightly capitate, light yellowish green; scales ± 2 mm long, linear, uniformly light green. Follicles not seen. Seeds not seen. Chromosome number: unknown.

Flowering time: —August to September, peaking from late-winter to early-spring, southern hemisphere.

Eponymy: — Kalanchoe × forbesiae is named for Helena Madelain Lamond Forbes (Forfar, Angus County, Scotland, 11 September 1900 –Durban, KwaZulu-Natal province, South Africa, 5 September 1959) ( Fig. 7 ). Forbes was appointed as a junior assistant at the Natal Herbarium (Herb. NH; now the KwaZulu-Natal Herbarium) in 1919. From 1936 to 1937 she spent time at the Royal Botanic Gardens, Kew, and afterwards at the National Herbarium in Pretoria (Herb. PRE), from 1938 to 1940. In 1940 she returned to the then Natal Herbarium to be its curator until she retired in 1955 ( Gunn & Codd 1981: 156). She was an authority on the flora of KwaZulu-Natal and among the taxa she described from the province was K. albiflora Forbes (1941: 37) , a name that is today widely included in the synonymy of K. luciae Hamet (1908: 256) .

Figures

FIGURE 5. The leaves of Kalanchoe ×forbesiae are weakly red-infused, but the peduncles, especially higher up, are more intensely redinfused. Photograph: Gideon F. Smith.

FIGURE 6. The corolla tubes and corolla lobes of K. ×forbesiae are virtually the same yellow colour, with the tubes being only faintly greenish-infused. Photograph: Gideon F. Smith.

FIGURE 7. Kalanchoe ×forbesiae commemorates Helena M.L. Forbes (1900–1959). Photographer unknown. Photograph © of the South African National Biodiversity Institute. Reproduced with permission.