Clustered robust palm climbing to 30-45 m. Stems without sheaths 30-50 mm in diameter, with 45-60 mm; internodes 35-50 cm long, although more commonly 18-25 cm. Leaf sheath moderately to profusely armed with black-tipped finely triangular, upward pointing or spreading spines; sheaths on upper portion of stem more sparsely armed; juvenile sheaths particularly profusely armed; dense brown-black indumentum present on mature sheaths, more sparse on juvenile sheaths; ocrea 20-30 cm long, dry, gradually tapering at the apex, reflexed, tattering longitudinally and disintegrating, dark tan mid-brown without, crimson-brown within, armed as the sheath although spines often concentrated at the apex, particularly on juvenile sheaths. Leaves up to 3.5m long; petiole 5-12 cm long, 1.5-2.5 cm. wide, mid to dark green with scattered brown-black indumentum, particularly on upper surface, abaxially rounded, adaxially lightly to moderately concave proximally becoming flattened in cross section distally, armed along the margins with inequidistant black-tipped angular spines up to 1.4 cm long, spreading in many directions; rachis 1.5-2 m long, shaped as the petiole, becoming more trapezoid in cross section then triangular in cross section distally, armed as the petiole proximally, spines becoming more sparse distally, with sparse brown indumentum present below; cirrus up to 1.5-2 m. long, triangular in cross section, only very sparsely armed with reflexed bulbous-based black-tipped spines, sparse brown indumentum below; leaflets always composed of a single-fold, 45-65 on each side of the rachis, equidistant, opposite to sub-opposite proximally, inequidistant, alternate distally, papyraceous, conspicuously pendulous, finely linear-lanceolate, base abruptly contracted, apex broadly to finely acuminate, often breaking off, 30-45 cm long (commonly up to 60 cm) 1.2-2.8 cm broad at the widest point, ± concolourous, glaucous blue-green, margins armed with inequidistant exceptionally fine, 5-8mm long, forward facing curved or angular black-tipped spines; 1 costulate midrib armed as the margins although spines much longer; acanthophylls 4.5-5 cm long. Inflorescences, numbering 6-12 produced simultaneously in the distal 1.5-2.2 m portion of stem; peduncle 12-20 cm long; prophyll ± 15 cm long; rachis branches up to 50 cm long, perpendicular to the main axis; rachis bracts glabrous, 1.5-1.8 cm long, decreasing distally, dry throughout, covered in dense brown-black indumentum, tapering to form a truncate triangular lobe abaxially, closely adpressed to the bract above; rachillae 18-25 cm long, pendulous, rachillae bracts campanulate-cylindrical, ± 5 mm long, dry throughout, triangular to broadly acuminate adaxially, each with a wide opening and a 1.5 m. long apiculum. Flowers in dyads, rarely triads, at anthesis ± 1 cm by 2.5-3.0 mm wide; calyx ± 6 mm long, excluding 1-1.5 mm long angular stalk, 2.5-3 mm wide, tubular in the basal 4 mm only, with 3 dark-tan, lightly striate, rounded to triangular, rarely acuminate, apex, 3.5 by 3 mm; corolla, tubular in the basal 2 mm only, with 3 valvate lobes ca. 7 by 2 mm, white or cream, with a bluntly acuminate apex; stamen filaments, brown, fleshy, angular, 3 mm by 1 mm broad, united into 1.5 mm long basal tube; anthers 3 mm by 1 mm broad; ovary ± 1 mm in diameter, stigma up to 5 mm. Fruit at maturity ovoid; 1– (rarely 2) seeded, 1.2-1.5 cm by 0.8-1.2 cm, with 17-20 vertical rows of scales. Seed smooth, ovoid, with lightly scalloped depression on one side, 0.8-1.3 cm long by 0.6-0.8 cm wide by 0.5 cm thick.
This species is commonly encountered in forest gaps and regrowth vegetation and responds well to selective logging activities. It is encountered on both terra firma and seasonally inundated forest.
Porijeklom iz, Cameroon, Central African Republic, Congo, Equatorial Guinea, Gabon, Democratic Republic of the Congo
Laccosperma robustum is very common species throughout its range and is distributed from SE Nigeria to the central Congo Basin.