Yucca harrimaniae Trel. — Harriman’s Yucca, the Spanish Bayonet of the Rocky Mountain West — is the compact, wickedly armed dwarf yucca of the Colorado Plateau, the Great Basin and the canyonlands of Utah. It is a plant with a wonderful discovery story: it was found by William Trelease, director of the Missouri Botanical Garden, when his train broke down at Helper, Utah, during the return journey from the legendary Harriman Alaska Expedition of 1899. Stranded while the locomotive was repaired, Trelease went botanising among the rocky slopes beside the railroad tracks and collected the little yucca that he would name in honour of Mrs. Mary Harriman, wife of the railroad tycoon Edward Harriman who had funded the expedition. It is a small, stemless, deceptively dangerous plant — neat, compact, rarely more than 40 cm tall, with rigidly sharp, concave leaves tipped with a spine capable of puncturing leather — forming clumps of rosettes on the rocky plateaux, piñon-juniper slopes and sagebrush hills of the intermountain West, from 1,000 to 2,700 m elevation. It is one of the hardiest yuccas in the genus, surviving temperatures of –30 °C and below.
This page covers the taxonomy, discovery history, varieties, morphology, ecology and cultivation of Yucca harrimaniae, and can be read alongside the species page on Yucca neomexicana (its eastern counterpart), the hub page on the genus Yucca and the broader agavoids guide.
Discovery: a broken-down train and a new species
The story of the discovery of Yucca harrimaniae is one of the most charming in the history of American botany. In the summer of 1899, the railroad magnate Edward Henry Harriman organised and funded a grand scientific expedition to Alaska, assembling a team of leading American scientists, artists and writers aboard the steamship George W. Elder. Among the participants was William Trelease (1857–1945), the director of the Missouri Botanical Garden and one of the foremost authorities on yuccas and agaves in the world.
On the return journey from Alaska, the expedition’s train stalled at Helper, Utah — a small railroad town in the Book Cliffs of central Utah, named for the “helper” locomotives that were attached to trains to push them over Soldier Summit. While the locomotive was being repaired, Trelease walked out into the rocky desert landscape beside the tracks and collected a small, spiny yucca that he had not seen before. He named it Yucca harrimaniae in honour of Mrs. Mary Williamson Harriman (1851–1932), Edward Harriman’s wife and a significant philanthropist in her own right, who had supported the expedition.
The name is sometimes cited as honouring the Harriman family collectively, but Trelease’s original intent was specifically to name the plant for Mrs. Harriman.
Taxonomy and nomenclature
Yucca harrimaniae was published by Trelease and belongs to the family Asparagaceae, subfamily Agavoideae, genus Yucca, subgenus Chaenocarpa — the dry-fruited, capsule-bearing yuccas. This subgeneric placement, confirmed by its dry, dehiscent capsules, separates it from the fleshy-fruited yuccas (subgenus Yucca) such as Yucca baccata, Yucca schidigera and Yucca valida.
POWO (Kew) accepts Yucca harrimaniae as a valid species. The FNA treatment includes Yucca neomexicana as a variety of Yucca harrimaniae (var. neomexicana), but POWO recognises both as separate species, supported by Clary’s (1997) molecular data showing them as “discrete and widely separated” in the ITS phylogeny. For a detailed discussion of this separation, see the species page on Yucca neomexicana.
| Family | Asparagaceae |
| Subfamily | Agavoideae |
| Genus | Yucca L. |
| Subgenus | Chaenocarpa (dry-fruited, capsule-bearing) |
| Species | Yucca harrimaniae Trel. |
Synonyms listed by POWO and FNA: Yucca gilbertiana (Trelease) Rydberg, Yucca harrimaniae var. gilbertiana Trelease (1907), Yucca harrimaniae var. sterilis Neese & S.L. Welsh, Yucca nana Hochstätter (1998), Yucca harrimaniae subsp. gilbertiana (Trel.) Hochstätter (2000).
Common names: Harriman’s Yucca, Spanish Bayonet, Dwarf Yucca, New Mexico Yucca (the latter sometimes applied to the species complex including var. neomexicana).
Varieties and related taxa
The circumscription of Yucca harrimaniae has varied depending on whether Yucca neomexicana and several other minor taxa are included. Under the broadest treatment (FNA), the species includes four infraspecific taxa. Under the POWO treatment (followed here), neomexicana is excluded as a separate species, and the remaining synonyms are collapsed into Yucca harrimaniae without formal varieties.
| Taxon | Status (POWO) | Notes |
|---|---|---|
| var. harrimaniae | Accepted (autonym) | The typical form; widespread across the intermountain West |
| var. neomexicana (Wooton & Standl.) Reveal | Separate species: Yucca neomexicana | East of the Continental Divide; NE NM, SE CO, W OK; white flowers; glaucous leaves. See species page |
| var. gilbertiana Trelease | Synonym of Yucca harrimaniae | Described from the Gilbert area, Arizona; sometimes treated at subspecific rank by Hochstätter |
| var. sterilis Neese & S.L. Welsh | Synonym of Yucca harrimaniae | Very restricted range in Utah; plants apparently sterile or with very low seed set; sometimes elevated to species rank as Yucca sterilis |
| Yucca nana Hochstätter | Synonym of Yucca harrimaniae | Dwarf form from Utah; one of the smallest yuccas (15–20 cm tall and wide); sometimes sold under this name |
The form sold as Yucca nana in the horticultural trade is particularly notable: a truly miniature yucca, only 15–20 cm tall and wide, native to Utah. Dave’s Garden describes it as “still uncommon in cultivation” and “one of the smallest Yuccas.” It is treated by POWO as a synonym of Yucca harrimaniae, representing the extreme dwarf end of the species’ morphological range.
Morphology
Yucca harrimaniae is a small, acaulescent or very short-caulescent, cespitose yucca — one of the most compact species in the genus. It forms dense to open colonies of rosettes, each typically small (15–40 cm tall and wide) and often asymmetrical. Stems, when present, are short (to 0.3 m) and typically hidden by the leaf rosette.
The leaves are 30–50 cm long and 1.8–4.3 cm wide, linear to spatulate-lanceolate (widest near the middle), concavo-convex (concave on the upper surface — a key character), rigid, pale green with brown edges. The margins are entire and filiferous, bearing white or brown curly filaments. The apex is pungently sharp — dangerously so. The leaves are stiff enough and sharp enough to puncture skin, clothing and even leather. As one grower recounts: “My neighbor’s sister lost an eye to this plant.” This is emphatically not a yucca to plant beside a path or a children’s play area.
The inflorescence is racemose (occasionally paniculate at the base), 35–70 cm tall — short by yucca standards, rarely exceeding 75 cm (less than 2.5 feet). The peduncle is scapelike, 10–20 cm long, less than 2.5 cm in diameter. The bracts are erect, proximal ones to 20 cm, distal ones 5–8 cm. A critical diagnostic: the lowest flowers open below the leaf tips — that is, the inflorescence arises within or just barely beyond the rosette, with its lower flowers nestled among or below the top of the foliage. This separates Yucca harrimaniae from Yucca angustissima, in which the inflorescence can be 1.2 m (4+ feet) tall and the lowest flowers open well above the leaf tips.
The flowers are pendant, broadly campanulate (broadly bell-shaped), with distinct tepals 4–5.3 cm long, yellow or greenish yellow, usually tinged with purple. This flower colour is a key diagnostic: the yellowish-green tepals with purple tinge distinguish Yucca harrimaniae from Yucca neomexicana (white flowers) and from Yucca angustissima (white to pale green, generally tapering at both ends).
The fruit is a dry, dehiscent capsule — confirming placement in the subgenus Chaenocarpa. The immature fruit can be cooked and eaten, though the skin is bitter.
Individual crowns are monocarpic — each rosette dies after flowering. However, the plant typically produces side shoots before death, ensuring the continuity of the colony.
Distribution and habitat
Yucca harrimaniae (sensu stricto, excluding Y. neomexicana) is native to the intermountain West of the United States: Utah (the core of the range), Nevada, western Colorado, north-eastern Arizona and northern New Mexico (west of the San Juan Mountains). The distribution is entirely west of the Continental Divide — the eastern counterpart is Yucca neomexicana.
The altitudinal range is 1,000–2,700 m — a broad band from the lower piñon-juniper woodlands to the upper sagebrush zone and even the lower margins of montane forest. The species grows on rocky plateaux, hillsides, rock outcrops, canyon rims, piñon-juniper slopes and sagebrush steppe. It is particularly associated with the red-rock sandstone landscapes of the Colorado Plateau and the Great Basin steppe. It is visible in several US National Parks, including Arches National Park, Canyonlands National Park and Capitol Reef National Park — some of the most spectacular landscapes in the American West.
The climate is classic intermountain continental: cold, dry winters with regular hard frost and snow; hot, dry summers; low total precipitation (250–400 mm per year). This environment makes Yucca harrimaniae one of the most cold-adapted yuccas in the genus.
How to distinguish Yucca harrimaniae from similar species
| Character | Yucca harrimaniae | Yucca neomexicana | Yucca angustissima | Yucca glauca |
|---|---|---|---|---|
| Inflorescence height | <75 cm | 40–70 cm | 120+ cm (4+ feet) | Up to 100 cm |
| Lowest flowers | Below leaf tips | Extend 0–20 cm beyond rosette | Above leaf tips | Within or just beyond rosette |
| Flower colour | Greenish yellow, purple-tinged | White | White to pale green | White to pale green |
| Flower shape | Broadly bell-shaped | Campanulate | Tapering at both ends | Bell-shaped |
| Leaf cross-section | Concave | Concavo-convex | Flatter | Flat to slightly concave |
| Leaf width | 1.8–4.3 cm | 0.7–2 cm (narrower) | 0.5–1.5 cm (very narrow) | <1.2 cm (very narrow) |
| Distribution | West of Divide: UT, NV, W CO, NE AZ | East of Divide: NE NM, SE CO, W OK | UT, AZ, NM, CO (overlapping) | Great Plains: AB to TX/NM |
Ethnobotany
Like other small yuccas of the intermountain West, Yucca harrimaniae was used by indigenous peoples for food, fibre and soap. The flowers were eaten raw or cooked. The immature fruit was cooked (the skin is bitter). The young flowering stem was peeled, cooked and eaten like asparagus. The leaf fibres were used for cordage. The saponin-rich roots were used to make soap and shampoo. In modern times, yucca extracts have been used as a foaming agent in root beer, alcoholic beer and cocktail mixers.
Cultivation
Climate suitability
Yucca harrimaniae is one of the hardiest yuccas in the genus. PFAF (Plants For A Future) cites hardiness to at least –30 °C. Dave’s Garden records survival at –29 °C (–20 °F). This places it in USDA zone 4 or colder — comparable to Yucca glauca, the hardiest yucca of the Great Plains.
However, Yucca harrimaniae has an important cultural caveat: it is intolerant of warm, humid climates. Dave’s Garden notes that “it seems somewhat intolerant of climates that stay too warm, making it a hard plant to keep alive in my southern California climate.” PFAF similarly notes that while it is tolerant of cool, damp weather, it does not thrive in warm, humid conditions. This is a plant of cold, dry, continental environments and it performs best in gardens that replicate those conditions: cold winters, hot dry summers, low humidity, excellent drainage.
Soil and drainage
Thrives in any well-drained soil but prefers a sandy loam. It is hardier when grown in poor, sandy soils. Excellent drainage is essential. The species grows on rocky outcrops, sandstone escarpments and thin soils over bedrock in its native habitat. In cultivation, a raised rockery, crevice garden, scree bed or trough is ideal.
Light
Full sun to semi-shade. PFAF notes that it can grow in light woodland — more shade tolerance than most desert yuccas.
Watering
Extremely drought-tolerant once established. No supplementary watering needed.
Growth rate and habit
Slow. The species slowly multiplies, forming a colony over time. Individual crowns are monocarpic (dying after flowering), but side shoots maintain the colony. The compact, low habit makes it outstanding for rock gardens, alpine plantings, crevice gardens, troughs and small-scale xeriscapes. The Yucca nana form (15–20 cm) is one of the smallest yuccas available and is perfect for miniature plantings.
Cold hardiness comparison
| Species | Approx. minimum temperature | Notes |
|---|---|---|
| Yucca glauca | –30 °C and below | The hardiest yucca; Great Plains; very narrow leaves |
| Yucca harrimaniae | –29 to –30 °C | Compact; concave leaves; intermountain West; intolerant of warm humidity |
| Yucca neomexicana | –25 to –30 °C | Miniature; glaucous; east of Divide; white flowers |
| Yucca filamentosa | –25 to –29 °C | Acaulescent; stoloniferous; tolerates humid climates; many cultivars |
| Yucca baccata | –20 to –25 °C | Wider leaves; fleshy fruit; different subgenus |
A warning
The terminal spines of Yucca harrimaniae are exceptionally sharp and rigid. This plant has caused serious injuries, including eye injuries. It should be positioned well away from paths, seating areas, play areas and any location where people or animals might brush against it. The beauty of this compact species should not obscure its genuine danger.
Propagation
Seed. Pollination in the native range depends on yucca moths. In European gardens, hand pollination is necessary. PFAF notes that hand pollination with a small paintbrush is straightforward and successful.
Division of offsets. The cespitose, colony-forming habit produces offsets that can be separated.
Pests and diseases
No major problems. Resistant to honey fungus, immune to rabbit browsing, deer-resistant. The primary risk is root rot in waterlogged soils and failure to thrive in warm, humid climates.
Conservation
Yucca harrimaniae (sensu stricto) is common and widespread across the intermountain West. It is not considered threatened. The variety sterilis (if recognised) and the dwarf form nana have very restricted ranges and may be of local conservation concern, but have not been formally assessed by the IUCN.
Authority websites and online databases
Plants of the World Online (POWO) — Royal Botanic Gardens, Kew
Accepted as a distinct species.
https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:270374-2
Flora of North America (FNA)
Treatment including var. neomexicana and var. sterilis.
https://dev.floranorthamerica.org/Yucca_harrimaniae
Utah Valley University — Native Plants
Detailed species account with discovery story, identification notes and Clary DNA summary.
https://www.uvu.edu/crfs/native-plants/yucca-harrimaniae.html
PFAF — Plants For A Future
Edible uses, cultivation and hardiness data.
https://pfaf.org/user/Plant.aspx?LatinName=Yucca+harrimaniae
NPS — Arches National Park
Species account in the context of the Colorado Plateau landscape.
https://www.nps.gov/arch/learn/nature/…
iNaturalist
Citizen-science observations.
https://www.inaturalist.org/taxa/56024-Yucca-harrimaniae
Bibliography
Trelease, W. — Original description of Yucca harrimaniae. Named for Mrs. Mary Harriman, discovered at Helper, Utah, during the return from the Harriman Alaska Expedition (1899).
Trelease, W. — “The Yucceae.” Report (Annual) of the Missouri Botanical Garden 13: 27–133, 1902. Foundational genus revision including Yucca harrimaniae.
Trelease, W. — Report (Annual) of the Missouri Botanical Garden 18: 225, 1907. Description of var. gilbertiana.
McKelvey, S.D. — Yuccas of the Southwestern United States, Part 2, 1947. Included Yucca neomexicana within Yucca harrimaniae.
Reveal, J.L. — in Cronquist, A. et al., Intermountain Flora 6: 530, 1977. Combination of Yucca harrimaniae var. neomexicana.
Clary, K.H. — 1997. Phylogeny, Character Evolution, and Biogeography of Yucca L. (Agavaceae). Ph.D. dissertation, University of Texas. ITS molecular phylogeny showing Y. harrimaniae and Y. neomexicana as “discrete and widely separated.”
Hochstätter, F. — Yucca nana. Succulenta 77: 72, 1998. Description of the dwarf form now treated as a synonym of Y. harrimaniae.
Hochstätter, F. — Yucca harrimaniae subsp. gilbertiana. Yucca I 1: 36, 2000. Subspecific combination.
Hess, W.J. & Robbins, R.L. — Treatment of Yucca harrimaniae in Flora of North America, vol. 26. The current standard floristic treatment.
Neese, E. & Welsh, S.L. — Description of Yucca harrimaniae var. sterilis. Utah endemic with low seed set.
Webber, J.M. — Yuccas of the Southwest. USDA Agriculture Monograph 17, Washington, 1953. Earlier treatment; Pacific Slope records now referred to Y. harrimaniae.
Molon, G. — Le Yucche. Ulrico Hoepli Editore, Milan, 1914. Early European monograph on yuccas.
Irish, M. & Irish, G. — Agaves, Yuccas, and Related Plants: A Gardener’s Guide. Timber Press, 2000. Practical cultivation advice.
Allred, K.W. — Flora Neomexicana, 2nd edition, vol. 1. Range Science Herbarium, Las Cruces, New Mexico, 2012.