Some plants are famous. Some are ubiquitous. Aloe × nobilis is both — and yet, after more than two centuries in continuous cultivation, nobody knows exactly what it is.
The Gold-Tooth Aloe has been in European gardens since at least the early 1800s, when Adrian Hardy Haworth described it in 1804. It has been sold in nurseries on every continent, planted in millions of Mediterranean landscapes, used as a parent to create one of the best-selling succulent cultivars on Earth (Aloe ‘Crosby’s Prolific’), and grown by countless hobbyists who know it simply as “that tough little green aloe with the yellow teeth.” Yet its parentage remains unresolved: experts have proposed at least four different cross combinations, Urs Eggli’s authoritative Illustrated Handbook of Succulent Plants lists the name as “of unresolved application that should be rejected,” and POWO hedges by suggesting the formula “Aloe arborescens or Aloe brevifolia × Aloe perfoliata” — a formula that is itself ambiguous, offering two different candidates for one of the parents.
What is beyond doubt is the plant itself: a compact, vigorous, prolifically suckering rosette with bright green, triangular leaves edged with conspicuous golden-yellow to white, sharp but flexible teeth — the “gold teeth” that give the species its common name. It forms dense clumps, flowers reliably in summer with branched orange-red inflorescences, tolerates heat, drought, frost, and neglect, and grows in any soil that drains. It is, in practical terms, one of the most successful garden aloes ever produced — whether by human design or by the chance encounter of pollen and pollinator in some long-vanished Cape garden.
Origins: A Mystery in Four Hypotheses
Family: Asphodelaceae Subfamily: Asphodeloideae Genus: Aloe Name: Aloe × nobilis Haw., Transactions of the Linnean Society of London 7: 23 (1804) POWO hybrid formula: Aloe arborescens or Aloe brevifolia × Aloe perfoliata (syn. Aloe mitriformis) Synonyms: Aloe mitriformis var. spinosior Haw. Common names: Gold-Tooth Aloe, Golden-Toothed Aloe, Green and Gold Crown, Noble Aloe
The parentage of Aloe × nobilis has been debated since the nineteenth century. The leading hypotheses, in order of frequency in the literature:
Hypothesis 1: Aloe mitriformis × Aloe brevifolia. The most commonly cited formula. Both parents are Western Cape endemics — mitriformis (the large, creeping Mitre Aloe) crossed with brevifolia (the compact, blue-grey Short-Leaved Aloe). The offspring would combine the vigorous suckering and green leaf color of mitriformis with the compact rosette form of brevifolia. This hypothesis is supported by the morphological description in Hortus Third (1976): “similar to Aloe mitriformis but leaves less concave above.”
Hypothesis 2: Aloe distans × Aloe brevifolia. Proposed by some authors and listed on Dave’s Garden. Aloe distans (now often included in Aloe perfoliata sensu lato) is another Western Cape creeping aloe, smaller than mitriformis but similarly prostrate.
Hypothesis 3: Aloe arborescens × Aloe mitriformis. Proposed in Hortus Third as an alternative. This would combine a large, shrubby Eastern Cape species with the creeping Western Cape mitriformis — a geographically unlikely cross in the wild but entirely possible in a garden setting.
Hypothesis 4: Aloe arborescens or Aloe brevifolia × Aloe perfoliata. The POWO formula, which essentially combines hypotheses 1 and 3 by leaving one parent ambiguous.
What we can say with confidence: Aloe × nobilis is an artificial hybrid — it does not occur in the wild. It has been in cultivation for over 200 years. At least one parent is almost certainly from the Aloe mitriformis/perfoliata complex (section Mitriformes). The other parent is probably Aloe brevifolia (section Breviflorae). The cross is old enough that the original grower, location, and circumstances are lost to history.
Morphological Description
Aloe × nobilis is a compact, stemless to very short-stemmed, vigorously suckering succulent. Individual rosettes reach approximately 15 to 30 cm tall and 20 to 30 cm in diameter — substantially smaller than Aloe mitriformis (20–30 cm diameter with trailing stems to 2 m) but larger than Aloe brevifolia (8–12 cm diameter).
Leaves. Triangular, thick, fleshy, bright green to light green — a noticeably lighter, more vivid green than the blue-grey or glaucous tones of either presumed parent. Leaf margins are armed with conspicuous, sharp but flexible, golden-yellow to white teeth that are the species’ most diagnostic character and the source of its common name. The inner leaf surface may also bear a few scattered teeth. Under strong sun or stress, the leaf tips and margins develop attractive rose to orange tones.
The Gold-Tooth Aloe is frequently confused with Aloe mitriformis (syn. Aloe perfoliata) in the nursery trade — both are green, suckering aloes with toothed leaves. The distinction is size: nobilis has much smaller rosettes and lighter green foliage than true mitriformis.
Inflorescence and flowers. Branched inflorescences rising 45 to 60 cm above the rosette, bearing tubular orange-red flowers. Flowering occurs in summer — a useful seasonal complement to the winter-blooming species that dominate the Aloe genus.
Growth rate. Fast. The species suckers extremely prolifically, rapidly forming dense, spreading clumps. This vigorous vegetative reproduction is a key horticultural asset — and an inherited trait passed on to the commercially important ‘Crosby’s Prolific.’
Horticultural Legacy: The Grandparent of ‘Crosby’s Prolific’
Aloe × nobilis occupies a pivotal position in aloe horticultural history as one of the two parents of Aloe ‘Crosby’s Prolific’ — the most commercially successful aloe hybrid in the world.
The parentage of ‘Crosby’s Prolific’ is: Aloe × nobilis × Aloe humilis var. echinata (now synonymized under Aloe humilis).
From Aloe × nobilis, ‘Crosby’s Prolific’ inherited its compact rosette form, robust constitution, prominent marginal teeth, and — most critically — its exceptionally prolific suckering habit (the trait for which the cultivar is named). From Aloe humilis, it inherited the white-spotted leaf surface and tuberculate texture that distinguish it from plain-leaved nobilis.
The genealogy goes deeper: since nobilis itself is probably derived from Aloe brevifolia and Aloe mitriformis, ‘Crosby’s Prolific’ carries the genetics of at least three or four wild species — brevifolia, mitriformis, and humilis at minimum, possibly arborescens or distans as well. This complex multi-species heritage may explain the cultivar’s exceptional vigor, adaptability, and wide tolerance of cultural conditions — the phenomenon of hybrid vigor (heterosis) that plant breeders have exploited for millennia.
Every ‘Crosby’s Prolific’ sold at Home Depot, Lowe’s, and garden centers worldwide is thus a great-grandchild of the nameless Gold-Tooth Aloe that first appeared in a European garden sometime before 1804.
Comparison with Its Presumed Parents
Aloe × nobilis vs. Aloe mitriformis Mill. (Mitre Aloe)
| Character | Aloe × nobilis | Aloe mitriformis |
|---|---|---|
| Rosette diameter | 20–30 cm | 20–30 cm (similar, but on trailing stems) |
| Stem | Stemless to very short | Long, trailing, up to 2 m |
| Growth habit | Compact, mounding, clumping | Procumbent, creeping, cascading |
| Leaf color | Bright green to light green | Blue-green to grey-green |
| Marginal teeth | Golden-yellow, conspicuous | Pale white to yellowish |
| Flower form | Branched, orange-red | Dense, capitate (rounded) heads, scarlet |
| Flowering season | Summer | Late winter to spring |
| Cold hardiness | –5 to –7 °C | –4 °C |
The main distinction: nobilis is a compact mound; mitriformis is a trailing cascader. The bright green color and golden teeth of nobilis are instantly recognizable.
Aloe × nobilis vs. Aloe brevifolia Mill. (Short-Leaved Aloe)
| Character | Aloe × nobilis | Aloe brevifolia |
|---|---|---|
| Rosette diameter | 20–30 cm | 8–12 cm (much smaller) |
| Leaf color | Bright green | Glaucous blue-grey |
| Leaf shape | Triangular, toothed | Short, fat, broad |
| Marginal teeth | Golden-yellow, prominent | White, softer |
| Suckering | Extremely prolific | Very prolific |
| Flower color | Orange-red | Scarlet-pink |
| Cold hardiness | –5 to –7 °C | –5 °C (similar) |
| Conservation | Not applicable (hybrid) | Endangered (<2,000 wild plants) |
Nobilis is roughly twice the size of brevifolia and much greener — the glaucous blue-grey of brevifolia has been largely overridden by the green inheritance from the mitriformis parent.
Cold Hardiness
Aloe × nobilis inherits frost tolerance from both presumed parents.
Beautiful Desert Plants (San Marcos Growers provenance): “Hardy to about 20 degrees F” (–6.7 °C).
Cacti.com: Cold tolerance 20 to 25 °F (–6.7 to –3.9 °C).
World of Succulents: USDA zones 9b to 10b.
Practical synthesis: USDA zones 9a to 11b. The species tolerates brief exposure to –5 to –7 °C, consistent with its presumed parentage from two Western Cape species adapted to mild coastal winters with occasional frost.
Optimal Growing Conditions
Light
Full sun to light shade. The species produces its best coloration (green with rose-tipped leaves) and most compact rosettes in full sun. In deep shade, it etiolates and becomes less floriferous. In hot desert climates (Phoenix, Palm Springs), light afternoon shade prevents scorching.
Temperature
Very high heat tolerance — one of the toughest aloes for hot, dry climates. Also tolerates moderate frost (see hardiness section).
Substrate
Undemanding. Standard succulent mix, sandy loam, rocky soil — the species is remarkably tolerant of a range of substrates, provided drainage is adequate.
Watering
Extremely drought-tolerant once established. Water sparingly; the species survives on rainfall alone in most Mediterranean climates. Avoid waterlogging.
Landscape Uses
Ground cover (the prolific suckering rapidly fills bare areas), rock gardens, edging, xeriscaping, container culture, dish gardens, terraria (open). Cacti.com recommends combining with winter-blooming aloes for a longer flowering show — the summer-flowering nobilis provides color when winter bloomers are dormant.
Hardiness Zone
USDA zones 9a to 11b.
Propagation
Offsets are produced in abundance and are the standard propagation method. Detach rooted pups from the clump margin and plant directly. The species roots easily and establishes rapidly.
Seed is rarely used — as a hybrid, seed-raised progeny may not be uniform.
Pests and Diseases
Mealybugs, scale, and aloe rust are the main concerns. The species is generally robust and disease-resistant in cultivation — far less prone to rot than many other aloes, reflecting its hybrid vigor.
Bibliography
Carter, S., Lavranos, J.J., Newton, L.E. & Walker, C.C. (2011). Aloes. The Definitive Guide. Kew Publishing, Royal Botanic Gardens, Kew. 720 pp.
Eggli, U. (ed.) (2001). Illustrated Handbook of Succulent Plants: Monocotyledons. Springer, Berlin.
Haworth, A.H. (1804). “Aloe nobilis.” Transactions of the Linnean Society of London 7: 23.
Liberty Hyde Bailey Hortorium (1976). Hortus Third. Macmillan, New York.
Authoritative Online Resources
- POWO — Plants of the World Online (Kew): Aloe × nobilis
- World of Succulents: Aloe × nobilis
- Garden Aloes: Aloe nobilis profile
- iNaturalist: Aloe × nobilis
- The Belmont Rooster: Aloe ‘Crosby’s Prolific’ parentage analysis