On the sandy mesas and piñon-juniper hillsides of central and northern New Mexico — where the Sangre de Cristo Mountains give way to the Rio Grande rift and the high desert rolls toward the Jemez caldera — a small, enigmatic yucca has puzzled taxonomists for nearly a century. Yucca intermedia, as its name declares, sits between other species in virtually every character: intermediate in leaf width, intermediate in inflorescence height, intermediate in flower size. It is either a perfectly good species, a stabilized hybrid, or a figment of taxonomic optimism — depending on which expert you consult. The debate is not resolved. What is beyond dispute is that this New Mexico endemic produces some of the largest and most beautiful flowers in the genus — cream bells tinged with rose or rosy brown, up to 7 cm long — on stalks that rise gracefully through the rosette in May and June. For gardeners and collectors, Yucca intermedia — a species in the genus Yucca — offers exceptional flowers, genuine cold hardiness, and the intellectual pleasure of growing a plant whose very identity is a botanical argument.
Quick Facts
| Scientific name | Yucca intermedia McKelvey |
| Family | Asparagaceae (subfamily Agavoideae) |
| Origin | Northern and central New Mexico (endemic) |
| Adult size | Rosettes small, occasionally caulescent to 1 m; flower stalk (5–)7–13 dm total |
| Hardiness | −20 to −26 °C (−5 to −15 °F) / USDA zones 5b–9 |
| IUCN | Not assessed (range-restricted endemic, but not rare locally) |
| Cultivation difficulty | 2/5 |
Taxonomy and Nomenclature
Yucca intermedia was described by Susan Delano McKelvey in 1947, in the second volume of her monumental Yuccas of the Southwestern United States (pp. 116–120, plates 44–47). The specific epithet intermedia is Latin for “in the middle” or “between” — a frank acknowledgment by McKelvey that this plant is morphologically intermediate between other Colorado Plateau yuccas. McKelvey herself recognized a second variety, var. ramosa, distinguished by paniculate (branching) inflorescences.
A contested identity. The taxonomic status of Yucca intermedia has been debated since its description. Three competing treatments coexist in the literature:
- POWO (current): Accepts Yucca intermedia as a separate species, native to northern and central New Mexico.
- Reveal (1977) / Hochstätter (1999): Treated it as Yucca baileyi var. intermedia or subsp. intermedia — a variety of the closely related Navajo yucca.
- Webber (1953): Believed Yucca intermedia to be a hybrid between Yucca glauca (soapweed yucca) and either Yucca angustissima (narrowleaf yucca) or Yucca baileyi (Navajo yucca).
The Flora of North America (Hess & Robbins, 2002) treats it as a species but reports Webber’s hybrid hypothesis. The New Mexico Rare Plant Technical Council (Ferguson, 2001) noted that the taxon is “taxonomically doubtful.” Wikispecies places it in series Glaucae — the soapweed yucca group — rather than alongside Yucca baileyi, which reinforces the morphological link to Yucca glauca.
For the purposes of this article, we follow POWO in treating Yucca intermedia as an accepted species, while noting the unresolved controversy.
Family and subfamily. Asparagaceae, subfamily Agavoideae (APG IV, 2016).
Synonyms (POWO)
- Yucca baileyi subsp. intermedia (McKelvey) Hochstätter (1999)
- Yucca baileyi var. intermedia (McKelvey) Reveal (1977)
- Yucca intermedia var. ramosa McKelvey (1947)
Common Names
English: narrowleaf yucca (used locally in New Mexico — confusing, since this name is also applied to Yucca angustissima). No widely established common name exists. Some New Mexico field guides use “intermediate yucca” — a literal translation of the epithet.
Morphological Description
Habit and Stem
Yucca intermedia is a cespitose (clump-forming) perennial that forms widely separated colonies — a growth pattern distinct from the dense clumps of Yucca baileyi or the massive spreading mats of Yucca angustissima. Each colony contains only 1–5 rosettes, usually small. Plants are acaulescent or occasionally caulescent, with erect, simple stems shorter than 1 m. This occasional stem development is a key morphological difference from the essentially always stemless Yucca baileyi.
Leaves
The leaf blade is linear (not lanceolate as in Yucca baileyi), plano-convex or plano-keeled, widest near the middle, measuring 33–65 × 0.5–0.8 cm — longer and narrower than in Yucca baileyi (25–50 × 0.6–0.9 cm). The texture is slightly flexible (vs. rigid in Yucca baileyi). Margins are entire, white to grayish — a distinctive pale margin visible in the field. The leaves are notably narrow: less than 1 cm (3/8 inch) wide, which is a diagnostic field character used by New Mexico wildflower guides.
Inflorescence and Flowers
The inflorescence is where Yucca intermedia truly distinguishes itself. It is mostly racemose but sometimes paniculate proximally (branched at the base) or occasionally paniculate and long-racemose distally — a variable architecture that prompted McKelvey to describe var. ramosa (paniculate forms found in the southeastern part of the range). The inflorescence arises within the rosettes and reaches (50–)70–130 cm in total height — approximately 1.5 to 2.5 times the length of the leaves. This ratio is a critical field diagnostic separating it from Yucca baileyi (inflorescence less than 1.5 times leaf length) and Yucca glauca (inflorescence 1.0–1.5 times leaf length). The inflorescence is glabrous, mostly green, with erect bracts.
The flowers are the species’ crowning glory — the largest of any stemless yucca in New Mexico. They are pendant, campanulate or rarely globose, with distinct tepals measuring 5.5–7 × 2–3.2 cm — cream or greenish, often tinged rose or rosy brown. This rose-brown flush on the outer tepals is a gorgeous and distinctive color that sets Yucca intermedia apart from the purer whites and greens of its congeners. Filaments reach 2.5 cm; anthers are 3.2–4.8 mm. The pistil is 1.5–3.2 cm; the style is white or pale yellowish green (7 mm), with lobed stigma. The cream-colored stigma (not dark green as in Yucca glauca) is a critical diagnostic for field identification in New Mexico.
Flowering occurs in May–June.
Fruits and Seeds
Fruits are erect, capsular, oblong-cylindric, occasionally constricted at the middle, measuring 5–5.7 × 2–2.5 cm. Dehiscence is septicidal. Seeds are glossy or dull black, thin, 6–10 mm.
Similar Species and Frequent Confusions
Yucca baileyi Wooton & Standl. — Navajo Yucca
The closest relative — formerly the same species in some treatments. Yucca intermedia differs in: occasional stem development (up to 1 m); longer, narrower, linear (vs. lanceolate), slightly flexible (vs. rigid) leaves; fewer rosettes per colony (1–5 vs. up to 15); taller inflorescence relative to leaf length (1.5–2.5× vs. <1.5×); and a more open colony structure (widely separated vs. compact). Flower size overlaps but Yucca intermedia reaches 7 cm (vs. 6.5 cm maximum in Yucca baileyi), with a distinctive rose to rosy-brown flush.
Yucca glauca Nutt. — Soapweed Yucca
The other putative parent in Webber’s hybrid hypothesis. Yucca glauca has a dark green stigma (vs. cream/pale yellowish green in Yucca intermedia), stiffer leaves, a distinct white marginal stripe (vs. white to grayish margins in Yucca intermedia), and a shorter inflorescence relative to leaf length (1.0–1.5× vs. 1.5–2.5×). Yucca glauca occurs in northeastern New Mexico on the high plains; Yucca intermedia in central and northern New Mexico — their ranges overlap in the transition zone between the Colorado Plateau and the Great Plains.
Yucca angustissima Engelm. ex Trel. — Narrowleaf Yucca
Both have narrow leaves, but Yucca angustissima has a much taller inflorescence (80–200+ cm) with the lowest flowers well above the leaf tips (vs. arising within the rosette in Yucca intermedia), and smaller, purely white to cream flowers (3–5.5 cm vs. 5.5–7 cm).
Comparative Table
| Character | Yucca intermedia | Yucca baileyi | Yucca glauca |
|---|---|---|---|
| Leaf shape | Linear, flexible | Lanceolate, rigid | Linear, rigid |
| Leaf width | 0.5–0.8 cm | 0.6–0.9 cm | 0.6–1.3 cm |
| Leaf length | 33–65 cm | 25–50 cm | 25–70 cm |
| Inflorescence / leaf ratio | 1.5–2.5× | <1.5× | 1.0–1.5× |
| Tepal length | 5.5–7 cm | 5–6.5 cm | 4–5.5 cm |
| Flower color | Cream, rose/rosy brown | Greenish white, purplish | Greenish white |
| Stigma color | Cream / pale green | Cream / white | Dark green |
| Rosettes per colony | 1–5 | Up to 15 | Variable |
| Stem | Occasional, to 1 m | Rare, to 0.2 m | Rare |
| Range | N. & C. New Mexico | AZ, CO, NM, UT | Great Plains, wide |
Distribution and Natural Habitat
Yucca intermedia is a New Mexico endemic — one of the very few yuccas restricted to a single U.S. state. Its range covers northern and central New Mexico, in the counties of Bernalillo, Cibola, Mora, Rio Arriba, San Miguel, Sandoval, Santa Fe, Socorro, Torrance, and Valencia. This distribution places it precisely in the geographic transition zone between the Colorado Plateau to the west, the southern Rocky Mountains (Sangre de Cristo range) to the north and east, and the Rio Grande rift running through the center.
The elevation range is 1,100–2,100 m.
The species grows in piñon-juniper (Pinus edulis–Juniperus monosperma) woodlands and adjacent grasslands — classic high-desert New Mexico habitat. Substrates are typically sandy to rocky, well-drained, on mesas, hillsides, and open scrubland.
The distribution pattern is significant for understanding the hybrid hypothesis. Yucca intermedia occurs precisely where the ranges of Yucca glauca (from the northeast, on the Great Plains) and Yucca angustissima / Yucca baileyi (from the northwest, on the Colorado Plateau) converge — exactly where one might expect stabilized hybrids to form.
Conservation
Yucca intermedia has not been formally assessed by the IUCN. The New Mexico Rare Plant Technical Council considered it for the state rare plant list in 2001 but concluded that even if taxonomically valid, it has “too great a range to be considered rare.” No CITES listing applies.
The main conservation concern is taxonomic rather than ecological: if the species is eventually subsumed into Yucca baileyi (as a variety) or dismissed as a hybrid swarm, it would lose its independent conservation identity. For now, POWO recognition ensures it is tracked as a distinct entity.
Cultivation
| Parameter | Value |
|---|---|
| Hardiness | −20 to −26 °C (−5 to −15 °F) / USDA zones 5b–9 |
| Light | Full sun |
| Soil | Very well-drained; sandy, rocky, mineral-rich |
| Watering | Very low; extremely drought-tolerant |
| Adult size | Variable — stemless to 1 m stem; colony typically small (1–5 rosettes) |
| Growth rate | Slow |
| Difficulty | 2/5 |
Light
Full sun is essential. The species grows on open, exposed mesas and hillsides in central New Mexico — one of the sunniest regions in the United States. In cultivation, provide the most exposed, south-facing position available.
Soil and Drainage
Fast-draining, mineral soil is the primary requirement. A mix of coarse sand, gravel, and pumice with minimal organic matter replicates the sandy-to-rocky substrates of the native habitat. The species tolerates a range of pH but prefers neutral to mildly alkaline conditions.
Watering
Less water is better. Central New Mexico receives 200–350 mm of rainfall annually, much of it concentrated in the summer monsoon season. In cultivation, once established, no supplemental irrigation is needed in most temperate climates. Overwatering, particularly in winter, leads to root and crown rot.
Cold Hardiness
Yucca intermedia is genuinely cold-hardy. Its native range at 1,100–2,100 m in northern New Mexico includes sites where winter temperatures regularly reach −20 to −26 °C (−5 to −15 °F). USDA zone 5b is a conservative estimate for well-drained soil. Santa Fe, near the center of the species’ range, has average winter lows around −12 °C (10 °F) with periodic plunges to −23 °C (−10 °F) or below.
As with all high-desert yuccas, the critical factor is drainage: dry cold is tolerated with ease; wet cold and waterlogged soil are fatal.
Container Growing
The small colony size (1–5 rosettes) and compact habit make Yucca intermedia a manageable container subject. Use a very gritty mineral substrate (70–80% inorganic) in a wide terracotta pot. The occasional stem development means some forms may grow taller than expected.
Growth Rate
Slow. The species forms widely separated colonies, suggesting relatively slow vegetative expansion.
What to Know Before Buying
Availability. Yucca intermedia is extremely rare in cultivation — arguably the rarest of the species covered in this silo. It is not offered by mainstream nurseries and is rarely listed even by specialist cold-hardy yucca growers. Seeds may occasionally appear in specialist exchanges, and wild-provenance material from central New Mexico is the most likely source.
Identity confusion. Plants labeled Yucca baileyi var. intermedia are the same entity. However, distinguishing Yucca intermedia from Yucca baileyi or Yucca glauca in the vegetative state is notoriously difficult — the “intermediate” character of the species works against easy identification. Flowering is needed for confident determination, and the rose-tinged tepals and cream-colored stigma are the most reliable diagnostics.
The hybrid question. If you are a purist who only grows “clean” species, the Webber hybrid hypothesis may give you pause. If you are a collector who values botanical complexity, Yucca intermedia is precisely the kind of plant that makes a collection intellectually stimulating. POWO accepts it as a species — and the flowers are gorgeous regardless of pedigree.
Propagation
Seeds
Sow fresh seeds in a very gritty, sandy mix at 15–21 °C. Pre-soak for 24 hours. Germination is slow and irregular (weeks to months). Given the rarity of the species in cultivation, seed propagation from verified wild material is the most promising pathway for introducing it to gardens.
Offsets and Division
The cespitose habit produces offsets, though colonies are smaller (1–5 rosettes) than in Yucca baileyi (up to 15). Detach offsets with a portion of rootstock and callus for 2–3 days before potting.
Pests and Diseases
Yucca intermedia is extremely trouble-free in appropriate conditions — full sun, rocky soil, sharp drainage.
Root and crown rot: The primary cause of loss, always linked to excessive moisture or heavy soil. Prevention through substrate selection is the only effective strategy.
Agave snout weevil (Scyphophorus acupunctatus): Not documented as a significant host. The high-elevation, cold native range limits weevil populations. However, monitor if growing alongside more susceptible agavoids in warmer zones.
Deer and rabbits: Highly resistant. The spine-tipped leaves deter most browsers.
Landscape Use
Yucca intermedia is a collector’s plant — rare, beautiful, and intellectually compelling.
Collector’s gardens: The primary use. For anyone assembling a comprehensive collection of western North American yuccas, Yucca intermedia fills a unique niche — the “missing link” between Yucca baileyi, Yucca glauca, and Yucca angustissima. Growing it alongside these putative parents creates a living illustration of speciation (or hybridization) in action.
Rock gardens: The compact colony size (1–5 rosettes) and relatively short stature make it suitable for detailed rock garden compositions. The rose-tinged flowers are a seasonal highlight.
High-desert native plantings: In its home state of New Mexico, Yucca intermedia belongs in any native-plant garden representing the piñon-juniper woodland ecosystem. Plant alongside Juniperus monosperma, Pinus edulis, Opuntia phaeacantha, Ephedra viridis, and Bouteloua gracilis.
Frequently Asked Questions
Is Yucca intermedia a real species or a hybrid?
That depends on which taxonomist you ask. POWO (the current global authority) accepts it as a species. The Flora of North America treats it as a species but notes Webber’s (1953) hypothesis that it is a hybrid between Yucca glauca and either Yucca angustissima or Yucca baileyi. Other authorities have treated it as a variety of Yucca baileyi. No molecular phylogenetic study has definitively resolved the question.
How does Yucca intermedia differ from Yucca baileyi?
Several characters: Yucca intermedia has linear (vs. lanceolate) leaves that are slightly flexible (vs. rigid); an inflorescence 1.5–2.5 times the leaf length (vs. less than 1.5 times); fewer rosettes per colony (1–5 vs. up to 15); occasional stem development (up to 1 m vs. rarely exceeding 20 cm); and a distinctive rose to rosy-brown flush on the flowers.
How can I tell Yucca intermedia from Yucca glauca in the field?
The most reliable character is stigma color: cream to pale yellowish green in Yucca intermedia, dark green in Yucca glauca. Additionally, the inflorescence-to-leaf-length ratio is higher in Yucca intermedia (1.5–2.5× vs. 1.0–1.5×), and the flowers are larger (5.5–7 cm vs. 4–5.5 cm) with a rose tinge.
Where can I find Yucca intermedia for sale?
This is one of the rarest yuccas in cultivation. Specialist native-plant nurseries in New Mexico are the most likely source. Seed exchanges focused on cold-hardy succulents occasionally list it. If you cannot source it, Yucca baileyi (the closest relative) offers a similar aesthetic.
Is Yucca intermedia cold-hardy?
Yes — USDA zone 5b or colder in well-drained soil. The native range at 1,100–2,100 m in northern New Mexico experiences severe winter cold (−20 to −26 °C). Dry cold is no problem; wet cold and waterlogged soil are the danger.
Reference Databases and Online Resources
- POWO — Yucca intermedia
- Flora of North America — Yucca intermedia
- GBIF — Yucca intermedia
- Wildflowers of New Mexico — Yucca intermedia
- Wikispecies — Yucca intermedia
Bibliography
- McKelvey, S.D. (1947). Yucca intermedia. In: Yuccas of the Southwestern United States, vol. 2: 116–120, plates 44–47. Arnold Arboretum, Harvard University.
- Webber, J.M. (1953). Yuccas of the Southwest. Agriculture Monograph, USDA 17: 1–97.
- Webber, J.M. (1960). Hybridization and instability of Yucca. Madroño 15: 187–192.
- Reveal, J.L. (1977). Yucca. In: Cronquist, A.J. et al. (eds.), Intermountain Flora 6: 530–534. Hafner Publishing.
- Hess, W.J. & Robbins, R.L. (2002). Yucca. In: Flora of North America Editorial Committee (eds.), Flora of North America North of Mexico, vol. 26: 423–439. Oxford University Press.
- Clary, K.H. (1997). Phylogeny, character evolution, and biogeography of Yucca L. (Agavaceae) as inferred from plant morphology and sequences of the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA. Ph.D. dissertation, University of Texas at Austin.
- Hochstätter, F. (1999). Yucca baileyi subsp. intermedia. Cactaceae Review 1(2): 21.
- Larson, J., Reif, B., Nelson, B.E. & Hartman, R.L. (2014). Floristic studies in north central New Mexico, U.S.A.: the Sangre de Cristo mountains. Journal of the Botanical Research Institute of Texas 8: 271–303.
- Allred, K.W. (2012). Flora Neomexicana, ed. 2, vol. 1: 1–599. Range Science Herbarium, Las Cruces, New Mexico.
- Molon, G. (1914). Le Yucche. Ulrico Hoepli Editore, Milano. 247 pp.