Agave havardiana Trel.
Havard's agave / Harvard century plant
Agave havardiana is the emblematic agave of the Chihuahuan Desert at higher elevations, distinguished by its remarkable cold hardiness, setting it apart from most of the genus. It forms compact, symmetrical rosettes of blue-grey leaves with strong marginal teeth and a well-developed terminal spine. It is a high-mountain plant that withstands regular snowfall and below-zero temperatures, making it ideal for cold, xeric gardens in high-altitude continental climates. It was described by William Trelease and named in honor of botanist Valery Havard.
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Overview
| Category | Classification |
|---|---|
| Family | Asparagaceae |
| Genus | Agave |
| Growth Habit | Compact, symmetrical rosette, medium-sized. Erect-spreading, stiff, blue-grey leaves. Produces sparse basal offsets. Short stem. |
| Conservation Status | Least Concern (LC) — IUCN. Stable populations in Big Bend and Chihuahuan highlands. |
| pH Target | 6.5–8.5 |
| Type | Calcareous, sandy-gravelly, dry, well-drained |
Origin & Habitat
Morphology
Broadly lanceolate, 50–80 cm long, 10–15 cm wide at mid-section, blue-grey with waxy pruinescence. Margins with reddish corneous teeth 5–10 mm, spaced 1–2 cm. Terminal spine 3–6 cm, channeled, dark brown.
ecoYellowish-green to reddish, 6–8 cm, in a dense panicle on a 4–7 m scape. Single bloom at end of life cycle (15–30 years). Pollinated by bats, hummingbirds, and nocturnal moths.
ecoShort, very robust caudex, up to 40 cm in diameter in old plants. Tissues adapted to freeze-thaw cycles.
ecoDeep root system for an agave, with roots penetrating deep rock crevices. Adaptation to high-mountain calcareous soils.
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Requirements
Soil & Substrate
Type
Calcareous, sandy-gravelly, dry, well-drained
groups Beneficial Associations
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Propagation Strategy
G
O
Every 5–7 years; very slow-growing. Prefer open ground in suitable climates.
No fertilization needed in ground. In pot, one application of low-nitrogen mineral fertilizer in spring.
Uses & Applications
Precautions / Toxicity
Irritating sap; teeth and spines are physically hazardous. No significant systemic toxicity. Heart edible after prolonged cooking.
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Plant Health
Root rot — uncommon in natural habitat given gravelly drainage; risk in cultivation if substrate retains moisture in winter.
Mealybugs (Pseudococcus spp.) — observed in greenhouse collections; treat with systemic insecticide.
Agave snout weevil (Scyphophorus acupunctatus) — threat in collections in warmer climates; preventive pheromone monitoring.
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"One of the few Agave species adapted to regular snowfall and repeated below-zero temperatures. Its use in cold continental landscaping (USDA zones 7–8 in Europe and the US) is growing as a cold-hardy alternative to tropical agaves."
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Scientific Integrity
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Sources
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Discussion
Disclaimer
This species record is provided for educational and informational purposes only. Jardín Roca Negra does not guarantee the accuracy or completeness of the data. Content is community-curated and may be subject to revision; it should not replace advice from a qualified botanist. This species may be toxic, invasive, or subject to legal restrictions — verify before handling or cultivating. Jardín Roca Negra accepts no liability for any harm arising from reliance on this information. Images are reproduced under Creative Commons or equivalent free licenses; credits are noted below each image.