Plant Family: Belongs to the Arecaceae/Palmae or Palm family, which includes the Coconut Palm (Cocos nucifera), the Date Palm (Phoenix dactylifera) and Talipot or Century Palm (Corypha umbraculifera)

Description: A very hardy, tall, graceful but viciously spined, solitary palm, up to 15 m tall (50 ft); trunk ringed, grey brown, 22-27 cm in diameter (9-11 in), armed with large quantity of black spines 8-10 cm long (3-4 in), particularly towards upper part of tree; leaves pinnately compound, plume-like, very long, up to 3 m long (10 feet), covered with grayish bloom; both leaves and petioles also possess long needle-like black spines; flowers born on spiny, woody spath covered with spines; flowers unisexual, yellow, with both sexes on the same stalk; male flowers have 6 stamens; fruit is round, light yellowish green, up to 5 cm diameter (2 in), with easily cracked shell and sweet, whitish pulp, often eaten by children; nut inside pulp is protected by extremely hard, bony endocarp, very difficult to crack open.

Natural Habitat: Likes full sun and good drainage; found at lower, drier elevations in Dominica; propagation by seed, but seeds take up to 6 months to germinate due to bony endocarp, and plant has very slow early growth.

Origin and Distribution: Native to open forests of Central and South America from Mexico to Argentina.

Uses: Caribs previously tapped young inflorescence and collected the juice for fermentation into a kind of wine; in subsistence regions, nut yields an oil, and in times of drought, tree felled and trunk core yields oil and starch for human consumption; today, tree primarily an ornamental, though use limited by very spiny trunk.

Indigenous Legends: Henry Bates, in The Naturalist on the River Amazons, stated, "These nuts, which are so hard as to be difficult to break with a heavy hammer, are crushed to a pulp by the powerful beak of [the Hyacinth] Macaw."

References:
Penelope N. Honeychurch. Caribbean Wild Plants and Their Uses. Macmillan, London, 1986
H.F. Macmillan. Tropical Planting and Gardening. Macmillan, London 1956
Mike Grey. Palms: Acrocomia aculeata. Palm and Cycad Society of Australia, Australia (pacsoa.org.au)
Macauba palm, Grugru Palm. Desert Tropicals, Arizona n.d. (desert-tropicals.com)
Chelsie Vandaveer. How was the spiny gru-gru utilized? Killer Plants and Herbal Folklore, Largo, Florida 2005 (killerplants.com)
Robert A. DeFilipps. Useful Plants of the Commonwealth of Dominica, West Indies. Smithsonian Institution, Washington, D.C. 1998