CYRTOSPERMA JOHNSTONII

Species

PROTOLOGUE:

Cyrtosperma johnstonii (W.Bull ex T.Moore & Mast.) N.E.Br., published in The Gardeners' Chronicle n.s. 18: 808 (23 December 1882).

Alocasia johnstonii W.Bull ex T.Moore & Mast., Gardeners' Chronicle n.s. 5: 603 (6 May 1876), in the report of Mr Bull's six new plants at the Brussels exhibition: "a species having purple, mottled stalks, furnished with short prickles arranged in groups, and arrow-shaped, erect, dark green leaves veined with red", said to come from New Guinea.¹² Hay (1988) had taken Bull's 1878 retail list as the place of publication and chose as lectotype the sterile leaves Bull sent to Kew in September 1878 (K000499264);⁴ Hay (2020) showed that the 1876 report, four months earlier than Wittmack's account of the same exhibition, validly published the basionym, so that the Kew sheet is not original material and a neotype was needed.⁵

Neotype: D.H. Nicolson 976, 3 May 1961, cultivated in the Bogor Botanic Garden, West Java, plant II.Q.F.35 (US, two sheets, barcodes 03822207 and 03822208; isoneotypes BO, L), designated by Hay (2020).⁵ Hay cites the basionym as Alocasia johnstonii W.Bull ex Mast.; IPNI and POWO credit the unsigned 1876 report to the Chronicle's editors, T. Moore and M.T. Masters, and that form is used here.¹,⁵ Masters printed the epithet as "johnsoni" and Bull always as "johnstoni", an orthographic error corrected to johnstonii under the Code.⁵

N.E. Brown's 1882 note records the first flowering in Europe, at the Compagnie Continentale d'Horticulture, Ghent, of the plant "which Mr. W. Bull introduced from the Solomon Isles, and sent out as Alocasia Johnstoni": peduncle like the petiole and armed with clusters of spines in an interrupted spiral; spathe ovate-lanceolate, acuminate, slightly convolute at the base, about 5 inches long, apparently brownish; spadix 2 inches by a quarter inch, brownish, flowering from the apex downwards; perianth of six free segments; six free stamens with exserted white anthers; ovary ovoid-oblong, one-celled, with two or sometimes one anatropous ovule fixed to the side of the cell. He calls it "the first Cyrtosperma that has been cultivated in European gardens".²

SYNONYMS:

HOMOTYPIC SYNONYMS: Alocasia johnstonii W.Bull ex T.Moore & Mast., Gard. Chron. n.s. 5: 603 (1876)

HETEROTYPIC SYNONYMS: N/A

ACCEPTED INFRASPECIFICS: N/A

DISTRIBUTION:

Solomon Islands: Solomon Is.¹

DISTRIBUTION NOTE: Known for over a century only from cultivation. Bull's exhibit of 1876 was labeled as introduced from New Guinea in 1875, but from 1878 his catalogs gave the Solomon Islands, and that origin was repeated without corroboration ever since; the one field record Hay could find in 1988 was a juvenile from open country at Hapan on Buka Island, labeled Caladium, "a very optimistic connection at best".⁴,⁵ The first wild-collected specimens are two juveniles gathered in 2013 by the National Museum of Natural Science, Taiwan, with the Solomon Islands forestry ministry, in the New Georgia group of Western Province: Hsu et al. SITW03642, beside a stream near Zaira village on Vangunu Island, and Yang et al. SITW01542, in forest at Sanapro village on Vella Lavella Island (TNM), both at very low elevation and both with the pink venation and incipient combs of upturned prickles of the species.⁵ A plant photographed by Patrick Blanc at Tenaru Falls on Guadalcanal in 2019 has the combed prickles but grows as a solitary-leaved forest-understorey plant, and may be something new.⁵ Herbarium records otherwise come from botanic gardens on four continents.⁶

SPECIES DESCRIPTION:

Gigantic suckering herb to c. 3 m tall, usually with one crown strongly dominant but eventually forming a clump of large crowns. Leaves several together, hastate to sagittate; petioles to 2.5 m long, irregularly and obliquely mottled white, green, brown and pink, heavily armed with the spines coalescing into oblique combs; costae bright pink in young plants, later the blades blotched reddish brown beneath and the costae green to brown; posterior lobes somewhat exceeding the anterior, to c. 70 cm long.⁴ Bogor plants measured by Alderwerelt had petioles 125–250 cm long, the prickles partly scattered and partly in obliquely transverse lines forming spiny crests, and blades green with a red-brown margin and minute carmine dots beneath.⁷

INFLORESCENCE:

Peduncle similar to but shorter than the petioles. Spathe deeply and narrowly boat-shaped, 9 to c. 40 cm long, rather abruptly more deeply and narrowly concave in the upper portion, erect, dark purple outside, pale dirty yellowish green within; spadix 7–25 cm long, with a short free stipe, somewhat glaucous; flowers hexamerous; anthers exserted at male anthesis; ovary 1–2-ovulate. Fruit and seed were unknown to Hay in 1988;⁴ fruiting plants have since been photographed in the Singapore Botanic Gardens (February 2019) and at Tully in North Queensland: an immature fruiting spadix c. 15 cm long on a collapsed peduncle, with the almost black remnant of the spathe persisting, purple-black tepals between the berries, and the berries ripening from the tip of the spadix downwards and turning yellow.⁵

ECOLOGY:

Lowland. The two 2013 collections are from a streamside and from forest at very low elevation, and the Buka juvenile from open country.⁴,⁵ In cultivation the plant thrives as a helophyte in submerged mud: at Bogor it grew far better as an emergent aquatic than as a terrestrial plant, with petioles alone reaching 2.5 m, and Hay doubts that it is a forest-understorey plant at all.⁵,⁷

DISTRIBUTION MAPS:

Hay 1988 Fig. 3 (putative field locality, Buka).

ETYMOLOGY:

Named by William Bull's nursery for a Johnston whose identity remains unknown: a search by Hay, David Mabberley and Lex Thomson in 2020 reached no conclusion.⁵ Masters printed the epithet "johnsoni" and Bull consistently "johnstoni", an orthographic error corrected to johnstonii under the Code, as Wittmack (1876) and Beccari (1885) already had it.⁵

NOTES:

1. Introduced to European cultivation by William Bull of King's Road, Chelsea, in 1875; exhibited as "Alocasia johnstoni" at the centenary exhibition of the Société Royale de Flore in Brussels in 1876, where Bull's new plants took the top gold medal, and again at Carlisle in 1877; first offered for sale in his catalog of 1878; figured in color by André in 1880, who suggested it might be a Lasia;⁸ and first flowered at the Compagnie Continentale d'Horticulture in Ghent in 1882, when Brown, who had suspected a Cyrtosperma from the leaves sent to Kew in 1878, received the bloom on 11 December and published the new combination twelve days later.²,⁵ Beccari's Cyrtosperma johnstonii of 1885 is an isonym.⁵ Brown published the species again with a plate and description in the Botanical Magazine in 1914, calling it the only Cyrtosperma then in cultivation.⁹

2. Phenotypically very variable with age and treatment: young plants show the brilliant pink costae, well-grown ones the dark blotching beneath, and an established clump carries the whole range of inflorescence sizes at once among crowns of different sizes.⁴

3. Diploid, 2n = 26.¹⁰ The inflorescences are protogynous and self-sterile, and plants bearing several at once fail to set seed, so Hay concluded in 1988 that the species is either sterile or physiologically self-sterile and that all cultivated plants are probably a single clone.⁴ In 2020 he showed that it does fruit, at Singapore and at Tully; that the diploid count rules out a sterile triploid, though not in principle a sterile diploid hybrid; and that its now-known wild occurrence makes sterility unlikely. Each bloom is mechanically self-incompatible, since pollen is shed only after all the stigmas have ceased to be receptive, and the rarity of fruit even where several blooms are open together suggests that the clonally identical cultivated plants are genetically self-incompatible as well.⁵

4. "Widely distributed in living botanical collections, but too slow growing to be of much commercial horticultural interest" was Hay's verdict in 1988;⁴ it is now a sought-after collectors' plant and most iNaturalist records are of cultivated specimens.³

5. A traditional medicine in Thailand; its flavonoid glycosides, rutin and isorhamnetin-3-O-rutinoside, and their hydrolysis products show antioxidant, antiproliferative and anti-inflammatory activity in vitro.¹¹

6. Hay (2020) counts at least three species in the Solomons archipelago, C. johnstonii, C. bougainvillense and C. merkusii, the last both as prickly wild plants and as gigantic, more or less unarmed edible forms, and two single-island endemics in the Louisiades, and expects more island endemics to turn up in the western Pacific.⁵

STORY:

STORY TITLE: Hay was wrong about this one, and said so

In 1988 Hay wrote that Cyrtosperma johnstonii almost never sets seed in cultivation and was probably a single clone: one plant, endlessly divided, in glasshouses since it entered horticulture in 1876 as Alocasia johnstonii.

In 2020 he took it back. The plant fruits, in Singapore in 2019 and in north Queensland. It is diploid. And it had been found in the wild in the New Georgia group of the Solomon Islands, first collected there in 2013. Not sterile at all: each bloom is mechanically self-incompatible, and the clone is probably genetically self-incompatible as well.

Thirty-two years is a long time to wait to correct yourself in print, and longer still to do it about your own monograph.

The plant meanwhile has a second career. It is a Thai traditional medicine, and since 2022 has been studied for its flavonoids.

REFERENCES:

1. Plants of the World Online, Royal Botanic Gardens, Kew — Cyrtosperma johnstonii.

2. Brown, N.E. 1882. Cyrtosperma Johnstoni, N.E.Br. Gardeners' Chronicle n.s. 18: 808 — protologue of the combination.

3. iNaturalist: Cyrtosperma johnstonii

4. Hay, A. 1988. Cyrtosperma (Araceae) and its Old World allies. Blumea 33: 427–469

5. Hay, A. 2020. Notes on the typification, origin, and fertility of Cyrtosperma johnstonii (Araceae–Lasioideae). Aroideana 43(3–4): 108–117.

6. GBIF occurrence download for Cyrtosperma, 2026-09-05 (60 records)

7. Alderwerelt van Rosenburgh, C.R.W.K. van. 1920. New or noteworthy Malayan Araceae. Bulletin du Jardin Botanique de Buitenzorg sér. 3, 1: 373

8. André, E. 1880. Alocasia Johnstoni. L'Illustration Horticole 27: 133–134, Pl. CCCXCV

9. Brown, N.E. 1914. Cyrtosperma Johnstoni. Curtis's Botanical Magazine ser. 4, 10: t. 8567