Agave titanota aka Chalk Agave

Agave titanota, or chalk agave, is an evergreen succulent. It belongs to the asparagus family, Asparagaceae. Its native range covers southwestern Puebla and northern Oaxaca, Mexico. It grows on rocky limestone slopes, ledges, and canyon walls. Its habitats include desert scrub and tropical dry forest. Kew places it in a seasonally dry tropical climate. Useful Tropical Plants reports an Endangered listing from 2020. Harvesting wild plants for mezcal has reduced mature plant numbers.

The plant forms an open rosette and may develop a short trunk. Young plants stand alone, though older plants may form offsets. Growth is slow, with maturity taking about 10–20 years. The leafy rosette reaches about 1.6–2.6 feet [0.5–0.8 m] tall. RHS gives a garden spread of 1.6–3.3 feet [0.5–1 m]. Another account records widths to 4.9 feet [1.5 m]. Pale, almost white leaves widen toward their tips. They reach about 1–2 feet [0.3–0.6 m] long. Curved brown spines line the edges and may join at their bases. Each leaf also ends in a long, twisted spine.

Yellow to yellow-green flowers appear from March to April. Their bright yellow stamens stand out on the tall stalk. The stalk may arch under the weight of its blooms. Flowers give off a musky scent toward evening. Bats pollinate them, and wind carries the seeds. RHS describes flower spikes of 9.8–19.7 feet [3–6 m]. Its overall height range reaches 26.2 feet [8 m]. Each rosette flowers once, sets seed, and then dies.

Grow this agave in full sun and soil that drains well. RHS lists both sandy and loamy soils across the pH range. Under glass, use peat-free cactus compost or loam with added sharp sand. Water during spring through autumn, letting the compost dry between waterings. Give less water during its winter rest. Outdoor plants tolerate drought and heat. LLIFLE reports survival near 27°F [-3°C] when dry. It still recommends avoiding frost; RHS assigns the warmer rating H1C. Chicago lists USDA zones 9–11.

Its rosette suits pots, patios, rock gardens, and beds among boulders. Birds and butterflies visit it, while deer tend to avoid it. It needs no pruning, but scale insects may attack. Wet soil can cause root rot. Its sap can irritate skin, and ingestion can harm pets. Wear gloves and protective clothing when handling it. People bake the harvested hearts, then ferment and distil them for mezcal. This processed use does not make the raw plant safe to eat.