Sonchus brassicifolius

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Description

"Treelet or tree , single-stemmed (commonly in cultivation) or apically poorly branched (in habitat), to 4.5 m tall (in cultivation, but recorded to 6 m for source material in habitat), 15–20 cm diameter, all parts of plants with abundant white latex, sometimes exuded from fi ssures on trunk in hot weather (at least in cultivation!). Stems unbranched or poorly branched towards apex, c. 6 cm diameter, and with large apical rosette, otherwise leafless with old leaves falling, waxy at first becoming dark green and eventually fawn coloured and somewhat fissured, solid, but clearly with transverse septae, leaf scars conspicuous, crescent-shaped, until fissure begin to form towards base and then obscured. Leaves large, rosettiform to spiralled, petiolate, petioles 10–22 cm long × 1.5–2.0 cm wide, deeply channelled above (appearing conduplicate), lamina (from apex of petiole to apex of lamina) 15–41 cm long (from base of lobe to apex 23–50 cm long) × 14–38 cm wide, midrib and primary venation prominent beneath, yellowish green above, margins entire, apex obtuse to rounded, sometimes almost mucronate at very apex. Infl orescence axillary, descending, with basal portion of peduncle c. 14 cm long beneath lowest petiolate leaf-like bracteole, and primary internode beneath first branching up to 24 cm, then apparently indeterminate and producing numerous capitula; bracteoles all sessile above primary bracteoles, markedly reduced in size from basal bracteole to those on pedicels, 20–105 mm long × 10–75 mm wide, usually markedly conduplicate, base rounded, lamina conspicuously pruinose above and below, margins entire, apex acute. Capitula ligulate, homogamous, 60–65 mm diameter; pedicels somewhat infl ated beneath involucre, c. 10 mm diameter; involucre 40–45 mm diameter × c. 25 mm tall, campanulate to turbinate at anthesis, post-flowering involucre contracting markedly above receptacle and appearing campanulateurceolate, producing c. 15 mm tall cone of phyllaries; phyllaries 3–4-seriate, all pruinose outside when fresh but with basal central area darkening when drying where wax covering is removed, outer phyllaries ovate-triangular, c. 7 mm long × c. 4 mm wide, margins glabrous, phyllary apices scarious, often brown recurved; middle phyllaries c. 15 mm × 5 mm wide, inner phyllaries 24 mm long × 4 mm wide, narrowly-lanceolate to linear, margins entire but ciliate in upper third and densely so towards apex along with densely pubescent outer surface and often appearing penicillate, hairs eglandular,apices acute; receptacle long-setiferous but only at corners of alveolae, setulae 5–6 mm long and persistent. Florets all ligulate, c. 100, all falling separately from capitulum after fertilization; corolla ligule 23–27 mm long × 2.2 mm wide, cadmium orange (RHS-BCC 8,), apricot (RHS-BCC 60 9), or tangerine orange (RHS-BCC 9, equivalent to RHSCC yellow-orange group 21A, 23A for individual corollas, and RHSCC Orange group 24A when viewing capitulum from front), apical teeth 5, 0.3–0.5 mm long, glabrous throughout except for a few variously-branched, multicellular eglandular hairs with stout basal cells on outside of teeth; corolla tube 10–11 mm long, yellowish, or orangish, white, setuliferous, setulae eglandular, of excentrically apexed twin-hairs; anther cylinder 8–9 mm long, completely exserted from ligule and corolla tube, apical anther appendages short-acute, triangular, orangish-yellow, basal anther appendages sagittate, entire; filaments attached level with sinus at base of ligule although filament based prominent lower down tube, glabrous throughout; style glabrous throughout; style base lacking basal node, glabrous; style arms orangish, becoming coiled with style arm appendages c. 0.5 mm long, brownish. Achenes 5–7.5 mm long × 3.5–4.5 mm wide (although numerous smaller, possibly sterile achenes exist in mature capitula measuring 2.5 mm × 2.5 mm), dorsiventrally flattened and winged with prominent apical notch bearing pappus, wings slightly buckled and undulating, wings and body longitudinally striate, sometimes also somewhat wrinkled along striae, glabrous, essentially concolorous, fawn to light brown; carpopodium a narrow amber-coloured annulus in mature achenes; pappus setae numerous, probably multiseriate and appearing as tuft in apical notch of achene, erect to spreading, 1.5 – 5 mm long, barbellate, fawn, and apical cell apices acute."A

Image sources

Habit and details (Hind & Johnson 2006: 315, t. 571 painting; 317 col. phot.; 319, 321 drawings).A
Flower cross and longitudinal section showing nectary (Bernardello & al. 2000: fig. 1 B,D).B

Distribution

The species is endemic to the Juan Fernández Islands (Morro Viñillo off of Juan Fernández Island, and Santa Clara Islands), Chile.A
Southern America: Juan Fernández Is. (Juan Fernández Is.nativeC)

Common names

English: Cabbage treeA; Spanish; Castilian (Chile, Republic of): Col de Juan FernándezA

Threat status

The species is Critically Endangered in the wild, but is cultivated in private gardens and public areas of Robinson Crusoe Island (formerly Juan Fernandez Island).A

Chromosome numbers

x = 9; the species is tetraploid with a chromosome number of 2n = 36.A,D

Biology and ecology

The natural habitats of Sonchus brassicifolius are probably coastal cliffs and coastal rocks (Hind & Johnson 2006).

The large orange-flowered capitula were observed to be pollinated by hummingbirds (Sephanoid sp.) and the flowers are self-incompatible (Anderson & al. 2001), which corresponds to the production of a relatively large amount of nectar with a rather low sugar concentration (Bernardello & al. 2000).A,B,E

Bibliography

A. Hind D. J. N. & Johnson N., Dendroseris litoralis in Curtis's Bot. Mag. 23: 314-324. 2006 (as Dendroseris litoralis)
B. Bernardello G. & al., Floral nectary structure and nectar chemical composition of some species from Robinson Crusoe Island (Chile) in Canad. J. Bot. 78: 862-872. 2000 (as Dendroseris litoralis)
C. Baeza C. M., Stuessy T. F., Tremetsberger K. & Urtubey E. - Lactucaceae in Zuloaga F. O., Morrone O. & Belgrano M. J. (eds.), Catálogo de las Plantas Vasculares del Cono Sur (Argentinia, Sur de Brasil, Chile, Paraguay y Uruguay) 2. 2008
D. Watanabe K., Index to chromosome numbers in Asteraceae.
E. Anderson G. J. & al., Breeding system and pollination of selected plants endemic to Juan Fernández Islands in Amer. J. Bot. 88: 220-233. 2001 (as Dendroseris litoralis)