Agave macroacantha aka Black Spined Agave

Agave macroacantha is an evergreen succulent known as black-spined agave. It belongs to the asparagus family, Asparagaceae. Its home range lies in Puebla and Oaxaca, Mexico. Wild plants grow on dry, rocky slopes near Tehuacan. They form dense clumps of rosettes on short stems. Garden plants reach about 2–3.3 feet [0.6–1 m] tall. Clumps spread about 2–3.3 feet [0.6–1 m] across. Oregon State and LLIFLE report wider clumps reaching 5 feet [1.5 m].

The stiff, narrow leaves spread out from each rosette's centre. Their colour ranges from blue-grey to pale blue-green. Leaves reach about 0.8–1.1 feet [0.25–0.35 m] long. Small brown teeth line their edges. Each leaf ends in a sharp, dark spine. Spine size and colour vary among wild plants. Some have black tips, while others have red-brown ones. The leaves near the centre turn red before flowering.

Plants may need at least 15 years before they flower. Chicago Botanic Garden lists the bloom season as May to June. Small green flowers carry a purple tint. A branched, dark red stalk rises above the leaves. It reaches about 6.6 feet [2 m], sometimes 9.8 feet [3 m]. The rosette dies after it flowers, according to Oregon State. Small plantlets may form on the flower stalk after bloom. Dark brown, oblong capsules hold dull black, triangular seeds. Bats, moths and hummingbirds visit the flowers as pollinators.

Grow this agave in full sun and soil that drains well. Light shade suits hot, low desert sites. The RHS lists sandy soil with an acid or neutral pH. Plants withstand drought, though hot inland gardens may need some water. Under glass, use cactus compost and give more water in summer. Reduce water in autumn and keep plants dry through winter. The RHS gives it H1C for UK conditions. Chicago lists USDA zones 9–11; Oregon State reports some brief frost tolerance.

Its firm rosettes suit gravel gardens, pots and patio displays. It needs no pruning, and offsets or seeds provide new plants. Scale insects may attack, but the RHS reports few disease problems. Wear gloves and protective gear, since contact can irritate skin. The plant also harms dogs and cats if they eat it. Tropical Plants Database records cooked flower buds as food. It also records use of the plant for mezcal. These prepared uses do not make the raw plant safe.