Until 1992, Macrozamia johnsonii did not officially exist. Every specimen, every herbarium sheet, every field observation was filed under Macrozamia moorei — the towering cycad of Carnarvon Gorge. Botanists knew there was a problem: the Macrozamia populations in northeastern New South Wales, around the Dalmorton area southwest of Grafton, looked different from the Queensland plants. Their fronds were bright green, not blue-green. Their leaves were flat in cross-section, not keeled. Their overall stature was somewhat smaller. But it took Ken Hill and David Jones to formally separate the two species in Telopea in 1992, naming the NSW plant for Dr Lawrie A. S. Johnson (1925–1997), the man who had revolutionised Australian cycad nomenclature three decades earlier with his 1959 reclassification. The result was the recognition of Macrozamia johnsonii as the largest cycad in New South Wales — a spectacular arborescent species with trunks to 3 m, crowns of up to 150 bright green fronds, and female cones up to 65 cm long weighing 14 kg.
Macrozamia johnsonii is also, paradoxically, one of the most restricted and threatened: listed as Endangered under NSW state legislation, with a total extent of occurrence of just 22,200 hectares and an area of occupancy of approximately 10,100 hectares in the forested ranges around Dalmorton. It belongs to the genus Macrozamia — the largest exclusively Australian cycad genus, with around 40 species — and within that genus its phylogenetic position is uniquely conflicted: molecular analyses place it at the first diverging branch within its clade, with substantial gene tree conflict suggesting a complex evolutionary history. This is the green giant of NSW — the cycad that hid in plain sight for a century, disguised as someone else.
Quick Facts
| Scientific name | Macrozamia johnsonii D.L.Jones & K.D.Hill |
| Family | Zamiaceae |
| Origin | NE New South Wales, Australia (Dalmorton area, SW of Grafton) |
| Adult size | Trunk to 1.5–3 m; 30–70 cm diameter; up to 150 fronds, 1.5–2.5 m long |
| Hardiness | −4 to −5 °C (25 to 23 °F) / USDA zones 9a–11 |
| IUCN | Least Concern (LC) — but Endangered (E) under NSW state legislation |
| CITES | Appendix II (all cycads) |
| Cultivation difficulty | 2/5 |
Taxonomy and Nomenclature
Macrozamia johnsonii was described by David L. Jones and Ken D. Hill in 1992 in Telopea (5(1): 31–34). Before this, the species was known informally as the New South Wales “form” or the “green form” of Macrozamia moorei. The separation was based on consistent morphological differences — leaf cross-section, leaf colour, seedling characters — that proved stable across populations and in cultivation.
The specific epithet honours Dr Lawrence Alexander Sydney Johnson (1925–1997), Australian botanist and former Director of the Royal Botanic Gardens Sydney, who was responsible for the major 1959 reclassification of Australian cycad nomenclature — the same revision that created Macrozamia communis and resolved the long-standing confusion with M. spiralis. Johnson was “a contemporary botanist and notable student of Macrozamia in the 1950s” (Haynes 2022). Naming this species for him was a fitting tribute.
Synonyms: Macrozamia moorei F.Muell. pro parte (partially) — the name previously applied to NSW populations.
Phylogenetic position: molecular phylotranscriptomic analysis (Cai et al. 2022) places Macrozamia johnsonii as the first diverging species within clade III (sub-clade A, corresponding to section Macrozamia), sister to all other remaining taxa in the clade. However, quartet support analysis reveals considerable gene tree conflict around this branch (q1 = 0.36, q2 = 0.29, q3 = 0.35) — indicating either incomplete lineage sorting, ancient hybridisation, or rapid early diversification. This conflicting phylogenetic position makes M. johnsonii one of the most evolutionarily intriguing species in the genus.
Common names: Johnson’s Cycad.
Morphological Description
Macrozamia johnsonii is a large, dioecious, evergreen, arborescent cycad — the largest Macrozamia species in New South Wales.
Trunk: massive, columnar, mostly 1.5–3 m tall (some sources cite up to 2.7 m of clear trunk; the NSW Scientific Committee gives 1.5 m as the typical height at maturity), 30–70 cm in diameter. Clothed in persistent leaf bases. The trunk develops through stages: subterranean caudex → aerial extension of the caudex → stout columnar trunk. Branching is extremely rare — PACSOA notes that in 30+ years of observation, branched wild trunks of this species have never been recorded (though one cultivated specimen in Brisbane has produced offsets).
Leaves: up to 150 per crown — an impressive number that creates a dense, palm-like appearance. Fronds are bright green (sometimes described as nearly yellow-green), 1.5–2.5 m long, initially standing almost vertically, then with age spreading in a graceful arching manner. The rachis is flat in cross-section — the single most important diagnostic character. Older plants often retain dead fronds that form a “skirt” around the trunk — an attractive contrast with the living crown above.
Leaflets: 150–250 per leaf, inserted on the rachis at about 40°, with stomata on both surfaces. Sharply pointed at the apex. A prominent whitish callous at the base where the leaflets join the rachis. The lower leaflets are progressively reduced to spine-like processes, as in M. moorei. The leaflets are slightly more flexible near the tips than in M. moorei, making the upper portion of the leaf somewhat less aggressive.
Cones: the largest of any NSW Macrozamia species.
- Male cones: cylindrical, green, curved. Male plants can produce multiple cones, with numerous cones in the leaf axils.
- Female cones: up to 65 cm long and 20 cm in diameter, heavily spined (apical spine 6–7 cm). Female plants bear up to 6 cones, with 3–4 being common. A mature cone can weigh 12–14 kg and contain over 200 seeds.
Seeds: the largest of any NSW Macrozamia — up to 4 cm long and 2.5 cm in diameter. Sarcotesta red to scarlet when ripe. Highly toxic.
Similar Species and Common Confusions
| Character | Macrozamia johnsonii | Macrozamia moorei | Macrozamia communis |
|---|---|---|---|
| Leaf cross-section | Flat | Keeled (V-shaped) | Flat |
| Leaf colour | Bright green to yellow-green | Dark blue-green | Dark green, dull |
| Maximum trunk height | 1.5–3 m | 7–9 m | Usually subterranean (to 2 m) |
| Fronds per crown | Up to 150 | Up to 150 | 50–100 |
| Female cone length | Up to 65 cm | Up to 90 cm | 20–45 cm |
| Distribution | NE NSW (Dalmorton) | Central QLD + disjunct NE NSW | Coastal NSW (Taree–Bega) |
| Conservation status | Endangered (NSW) | Near Threatened | Least Concern |
The flat-vs-keeled diagnostic: the single most reliable field character separating M. johnsonii from M. moorei is the leaf cross-section. Hold a leaf and look at the underside of the rachis: flat = M. johnsonii; V-shaped keel = M. moorei. The colour difference (bright green vs. blue-green) is also useful. Seedlings of the two species differ markedly in several characters, as documented by Jones & Hill (1992). In the nursery trade, the two are frequently confused — provenance is the best insurance: NE NSW = M. johnsonii; central QLD (Carnarvon, Springsure) = M. moorei.
Distribution and Natural Habitat
Macrozamia johnsonii is endemic to a highly restricted area in far northeastern New South Wales, centred on the Dalmorton area southwest of Grafton, in the ranges of the northern tablelands and upper Clarence River catchment. Notable populations are known from Boyd River and surrounding ranges. Cultivated specimens can be seen in gardens in Grafton and Nimbin (north of Grafton), where two enormous plants virtually overshadow the owner’s home.
The species has a total extent of occurrence of approximately 22,200 hectares and an area of occupancy of approximately 10,100 hectares (Binns & Meek 2008). Of the total population, approximately 59% occurs in State Forest, 30% in National Park, and 11% on private land.
The habitat is tall wet sclerophyll forest and margins of rainforest, generally on steep slopes. The species grows on both sides of watercourses (e.g. Boyd River), in more mesic conditions than the semi-arid gorge habitat of M. moorei.
Climate in the native range:
| Parameter | NE NSW (Dalmorton–Grafton ranges) |
|---|---|
| Mean annual temperature | 16–20 °C |
| Mean winter minimum | 4–8 °C |
| Historical minimum | −3 to −5 °C (frost regular on the ranges) |
| Mean summer maximum | 26–32 °C |
| Annual rainfall | 800–1,200 mm |
| Köppen classification | Cfa (humid subtropical) |
The habitat is wetter and more sheltered than that of M. moorei (which receives only ~500 mm), but still experiences regular frost on the ranges — making M. johnsonii reasonably cold-hardy.
Conservation
Macrozamia johnsonii presents a paradoxical conservation situation: it is listed as Least Concern (LC) on the IUCN Red List (global assessment), but as Endangered under New South Wales state legislation (NSW Threatened Species Conservation Act). In 2012, the NSW Scientific Committee explicitly rejected a proposal to delist it, concluding that the species “remains eligible to be listed as an Endangered species” because it faces “a very high risk of extinction in New South Wales due to its highly restricted geographic distribution and a projected continuing decline in the near future.”
Threats:
- Forestry operations: the most significant threat. 59% of the population occurs in State Forests, and modelling predicts that 21–32% of M. johnsonii habitat in State Forests will be logged in the next 100 years.
- Phytophthora cinnamomi: the root-rot pathogen is a potential threat, as M. johnsonii grows in wet forest conditions suitable for the pathogen’s spread.
- Fire regime changes: mature plants resprout after fire (the crown is fire-tolerant), but seedlings and juvenile plants are vulnerable. Altered fire regimes — either increased frequency or fire suppression — can affect population structure.
- Restricted range: the total extent of occurrence (22,200 ha) falls within the IUCN geographic range threshold for Endangered status.
Cultivation
| Hardiness | −4 to −5 °C (25 to 23 °F) / USDA zones 9a–11 |
| Light | Full sun to partial shade; full sun preferred for best crown form |
| Soil | Well-drained; tolerates a range of soils |
| Watering | Regular; appreciates more moisture than M. moorei |
| Adult size | Trunk 1.5–3 m; crown spread 3–4 m |
| Growth rate | Slow to moderate (near-continuous leaf production once trunk forms) |
| Difficulty | 2/5 |
Macrozamia johnsonii is a majestic cycad in cultivation — one of the most impressive landscape plants in the Australian cycad flora. Its bright green foliage and symmetrical crown give it a warmer, more tropical aesthetic than the blue-green, semi-arid M. moorei.
Light: full sun is preferred for the best crown development. Like M. moorei, this is a species of open to semi-open habitats. It tolerates partial shade but may become less compact.
Soil: well-drained, but more flexible than M. moorei. The native habitat includes wet sclerophyll forest on a range of soil types. In cultivation, any freely draining substrate is suitable.
Watering: regular. The native range receives 800–1,200 mm of fairly evenly distributed rainfall — significantly more than the 500 mm of semi-arid M. moorei. In cultivation, M. johnsonii appreciates more moisture and responds well to supplemental watering during dry periods.
Cold hardiness: the native range includes ranges where frost is regular, with historical minima of −3 to −5 °C. USDA zone 9b minimum for permanent outdoor planting, with the standard half-zone safety margin applied. In European Mediterranean climates (Côte d’Azur, Liguria, coastal Var), the species is suitable for open positions in zone 9b and above. In zone 9a, a sheltered position is advisable — the aerial trunk exposes the meristem to radiative frost, and an abnormally cold winter (1956, 1985, 2012-type events) could cause irreversible damage to a specimen that has taken decades to develop. Winter protection measures (fleece wrapping of the crown, root-zone mulch, dry autumn regime) are recommended in marginal climates.
Mealybugs: a noted problem. The dense crown of up to 150 closely spaced leaves creates poor air circulation — ideal conditions for mealybug infestations. Regular monitoring and treatment with horticultural oil or systemic insecticide are recommended.
Container culture: well suited to large containers in the juvenile phase. Mature trunking specimens will eventually outgrow containers but can remain in large pots for many years.
Buying Advice
Availability: Macrozamia johnsonii is more commonly offered than its Endangered status might suggest — seed-grown plants from cultivated parents are available from specialist cycad nurseries in Australia and internationally. It is more frequently seen in cultivation than the rarer wild populations would predict, because it is an outstanding landscape plant. Seeds and young plants are sometimes offered.
Identification: verify the flat leaf rachis and bright green colour to distinguish from M. moorei (keeled rachis, blue-green). Provenance: NE NSW origin = M. johnsonii; central QLD = M. moorei.
Propagation
Seed: the standard method. Clean the red sarcotesta (gloves — toxic) and sow at 25–30 °C in well-drained mix. Germination is cryptocotylar. No pretreatment required. Seedlings of M. johnsonii differ markedly from those of Macrozamia moorei in several characters (Jones & Hill 1992).
Offsets: extremely rare in the wild; one cultivated specimen in Brisbane has produced offsets from a raised garden bed — probably due to root disturbance.
Pests and Diseases
Mealybugs: the most significant pest problem. The large number of closely spaced leaves in the crown provides poor light penetration and air circulation — conditions that mealybugs exploit. Treat promptly with horticultural oil or systemic insecticide.
Phytophthora cinnamomi: a potential threat in wet conditions, particularly in the wild. In cultivation, ensure adequate drainage.
Toxicity: all parts are highly toxic (cycasin, macrozamin). Seeds are the most dangerous part. Toxic to dogs, cats, livestock, and humans.
Landscape Use
Macrozamia johnsonii is one of the most majestic cycads for landscape use in warm-temperate and subtropical gardens. The bright green foliage — warmer and more vivid than the austere blue-green of M. moorei — gives it a lush, tropical presence that is irresistible. A trunked specimen with 100+ fronds forming a dense, symmetrical crown is a landscape statement that no palm or tree fern can match for sheer prehistoric grandeur. Use it as a specimen tree in a lawn, at an entrance, or as the centrepiece of a cycad garden. The retained dead-frond “skirt” on trunked specimens adds character and can be left in place for a naturalistic effect or removed for a cleaner look. Pair with M. moorei for a stunning contrast of green vs. blue-green. Plant with Livistona palms, Cyathea tree ferns, or Xanthorrhoea grass trees for an all-Australian planting of extraordinary depth.
Caution: the sharply pointed leaflets and the spine-like lower leaflet processes, combined with the heavily spined cones (6–7 cm spines), make seed collection a formidable exercise — PACSOA notes that collectors have been seen cutting fronds to access the cones without being repeatedly spiked. Do not plant adjacent to walkways.
Frequently Asked Questions
How do I tell Macrozamia johnsonii from Macrozamia moorei?
Hold a leaf and look at the underside of the rachis. Flat = M. johnsonii. Keeled (V-shaped) = M. moorei. The leaf colour also differs: bright green to yellow-green in M. johnsonii; dark blue-green in M. moorei. Provenance is diagnostic: NE NSW (Dalmorton area) = M. johnsonii; central QLD (Carnarvon, Springsure) = M. moorei.
Why is it Endangered in NSW but Least Concern globally?
The IUCN global assessment (LC) considers the species’ overall survival prospects. The NSW state assessment focuses specifically on the Australian context, where the species has a highly restricted distribution (~22,200 ha extent of occurrence) and faces ongoing threats from forestry operations. The NSW Scientific Committee rejected a proposal to delist it in 2012, maintaining Endangered status.
Is Macrozamia johnsonii cold-hardy?
Reasonably — frost is regular in its native range, and it tolerates −4 to −5 °C. USDA zone 9b minimum for permanent outdoor planting, with winter protection recommended in marginal European climates. It is somewhat less cold-hardy than M. moorei (which comes from a more continental, frost-prone climate) but hardier than the subtropical M. miquelii.
Authority Websites and Databases
POWO — Plants of the World Online (Kew)
https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:968150-1
Accepted species. Native range: NE New South Wales. Subtropical biome. IUCN: Least Concern. EDGE score −8.16 (position 904).
World List of Cycads — cycadlist.org
https://cycadlist.org/scientific_name/396
First published in Telopea 5(1): 31 (1992). Etymology: honouring Dr L. A. S. Johnson (1925–1997), Australian botanist, former director of the Royal Botanic Gardens Sydney.
PACSOA — Palm and Cycad Societies of Australia
https://pacsoa.org.au/wiki/index.php/Macrozamia_johnsonii
The most detailed grower’s account. Previously the NSW “green form” of M. moorei, separated by Hill & Jones 1992. Trunk to 3 m, up to 150 fronds, flat leaves, female cones to 65 cm / 14 kg / 200+ seeds, largest seeds of any NSW Macrozamia. Grafton and Nimbin cultivated specimens. White callous at leaflet base. Dead-frond “skirt.” Branching extremely rare.
NSW Scientific Committee (2012) — Determination to reject delisting
https://www.environment.nsw.gov.au/topics/…
Official determination: Endangered in NSW. Extent of occurrence 22,200 ha, area of occupancy 10,100 ha. 59% in State Forest, 30% in National Park. Forestry operations the primary threat. Projected continuing decline.
NSW PlantNET — Macrozamia johnsonii
https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/…
Official NSW Flora: massive aerial trunk 2–5 m, 30–70 cm diameter. Synonym: M. moorei pro parte.
Cai, B., et al. (2022) — Phylotranscriptomics of Macrozamia
Annals of Botany 130(5): 783–797 (PMC9670756)
First diverging species in clade III (sub-clade A). Considerable gene tree conflict (q1=0.36, q2=0.29, q3=0.35). Flat leaves illustrated (Fig. 1E). Conflicting phylogenetic position between sub-clade A and sub-clade B.
Bibliography
Binns, D. L., & Meek, P. (2008). Population size, habitat and conservation status of an Endangered species, Macrozamia johnsonii (Zamiaceae). Cunninghamia, 10, 373–380.
Cai, B., Liddle, P., Lindstrom, A., et al. (2022). Phylotranscriptomics reveal the spatio-temporal distribution and morphological evolution of Macrozamia, an Australian endemic genus of Cycadales. Annals of Botany, 130(5), 783–797.
Hill, K. D. (1998). Cycadophyta. Flora of Australia, 48, 597–661.
Jones, D. L., & Hill, K. D. (1992). Macrozamia johnsonii, a new species of Macrozamia section Macrozamia (Zamiaceae) from Northern New South Wales. Telopea, 5(1), 31–34.
Jones, D. L. (2002). Cycads of the World (2nd ed.). New Holland Publishers, Sydney.
Whitelock, L. M. (2002). The Cycads. Timber Press, Portland.