In the jarrah forests of southwestern Australia, beneath the towering canopy of Eucalyptus marginata, a cycad forms the understorey as far as the eye can see. Macrozamia riedlei — the Zamia Palm — is so ubiquitous in this landscape that the early colonists simply called it “the zamia,” as though no other cycad existed. For the Noongar people, it was far more than a plant: it was jeeriji (also written djiriji, baian, koondagoor, quinning — different names for different parts and products), a staple food source processed by a sophisticated fermentation and leaching technique called mordak that archaeological evidence dates to at least 13,000 years ago. This is a plant that fed Australia’s First Nations for millennia before European contact — and then promptly poisoned the settlers who ate its seeds raw.
The species belongs to the genus Macrozamia — the largest exclusively Australian cycad genus, with around 40 species — but within that genus it is distinctive: smaller, glossier, and flatter-leaved than the other two Western Australian species (Macrozamia fraseri and Macrozamia dyeri), usually trunkless, and confined to the jarrah forest belt from Dwellingup to Albany. With an estimated 100,000–120,000 mature individuals, it is one of the most abundant cycads in Australia — and one of the most culturally significant plants on the continent.
Quick Facts
| Scientific name | Macrozamia riedlei (Fisch.) C.A.Gardner |
| Family | Zamiaceae |
| Origin | Southwestern Western Australia |
| Adult size | Usually trunkless (rosette 0.5–2 m); trunk to 2 m in old specimens; fronds 1–2.2 m |
| Hardiness | −2 to −4 °C (28 to 25 °F) / USDA zones 9b–11 |
| IUCN | Least Concern (LC) |
| CITES | Appendix II (all cycads) |
| Cultivation difficulty | 2/5 |
Taxonomy and Nomenclature
The species was first described as Cycas riedlei by Friedrich Ernst Ludwig von Fischer, based on a specimen collected at King George Sound (Albany, Western Australia) and held at the Paris Museum. Charles Gardner transferred it to Macrozamia in his Enumeratio Plantarum Australiae Occidentalis (1930), using the orthographic variant M. reidlei and citing specimens from Collie, Manjimup, Bow Bridge, and other sites south of Perth.
The specific epithet honours Anselme Riedlé (1775–1801), a French gardener and botanical collector who participated in Nicolas Baudin’s expedition to Australia and died of dysentery on Timor at the age of 26 — one of the many forgotten botanical martyrs whose names survive only in the plants they collected.
Taxonomic confusion with Macrozamia fraseri: for much of the 20th century (from the 1950s onwards), Gardner and Bennett lumped all three southwestern Australian Macrozamia species under the single name M. riedlei. It was not until Ken Hill’s revision at the end of the 20th century that Macrozamia fraseri was restored as a distinct species. The two do not co-occur: Macrozamia fraseri grows on the Swan Coastal Plain (Perth, Mandurah to Jurien Bay) while Macrozamia riedlei is a jarrah forest species of the Perth Hills and the southwest. The key diagnostic: Macrozamia riedlei has flat or only slightly keeled leaves, while Macrozamia fraseri has distinctly keeled (V-shaped) leaves and larger cones.
Common names: Zamia, Zamia Palm (the default name used by Western Australians for any Macrozamia); Noongar names: jeeriji, djiriji, baian, koondagoor, quinning (different names for the plant, its parts, and its products).
Morphological Description
Macrozamia riedlei is a small to medium, dioecious, evergreen cycad — usually trunkless, presenting as a ground-level rosette.
Trunk: short or subterranean, seldom arborescent; barrel-shaped, up to 0.5 m tall and 25–40 cm in diameter when emergent. Old specimens can develop a trunk to 2 m, but this is uncommon. The bole is protected underground and regenerates new leaves following fire.
Leaves: 12–30 per crown, rigid, upright to gracefully arching, 1–2.2 m long. The leaf is flat to slightly keeled in cross-section (opposing leaflets inserted at 130–180° on the rachis) — the key character distinguishing this species from the more strongly keeled Macrozamia fraseri. The rachis is not twisted, straight or slightly arched, stiff. Leaves are glossy dark green — noticeably glossier than the other WA species.
Leaflets: simple, linear, (23–)35–40(–48) cm long and (5–)7.5–11(–15) mm wide, weakly discolorous, with flat margins and a spiny apex. Narrowly spaced.
Cones:
- Male cones: spindle-shaped, 29–41 cm long, 11–15 cm diameter. Microsporophyll with apical spine 8–75 mm long. Longer and narrower than female cones.
- Female cones: ovoid, 25–35 cm long, 14–18 cm diameter. Barrel-shaped, pineapple-like. Female plants typically bear 1–3 cones. Cones mature in spring (September–October) and can contain up to 300 seeds.
Seeds: large, oblong to ovoid, with a bright red (or orange) fleshy sarcotesta. Highly toxic.
Coralloid roots: nitrogen-fixing cyanobacteria are harboured in coralloid roots that are well buried beneath the soil surface — deeper than in some other Macrozamia species. The toxins cycasin and macrozamin are produced by these symbiotic cyanobacteria and distributed throughout the plant.
Similar Species and Common Confusions
| Character | Macrozamia riedlei | Macrozamia fraseri | Macrozamia dyeri |
|---|---|---|---|
| Leaf cross-section | Flat to slightly keeled | Distinctly keeled (V-shaped) | Keeled |
| Leaf glossiness | Glossy | Less glossy | Variable |
| Cone size | Smaller | Larger | Larger |
| Trunk | Usually trunkless | Usually trunkless to short trunk | Short to medium trunk |
| Distribution | Jarrah forest belt (Dwellingup–Albany) | Swan Coastal Plain (Perth–Jurien Bay) | South coast / Esperance |
| Habitat | Jarrah forest understorey, lateritic soils | Coastal plain, sand over limestone | South coastal scrub |
The most important practical point: Macrozamia riedlei and Macrozamia fraseri do not co-occur. If you see a trunkless Macrozamia in the Perth Hills jarrah forest, it is almost certainly M. riedlei. If you see one on the Swan Coastal Plain (Kings Park, Bold Park, suburban Perth), it is almost certainly M. fraseri. The confusion arose because Gardner and Bennett treated them as a single species for decades.
Distribution and Natural Habitat
Macrozamia riedlei is endemic to southwestern Western Australia. Populations occur from Dwellingup (south of Perth) to Albany and further west to the coast — a range broadly coinciding with the jarrah forest belt. It also occurs in some locations on the coastal plain. The species is widespread and abundant, with an estimated 100,000–120,000 mature individuals and a generation length of approximately 60 years.
The primary habitat is dense stands as an understorey plant in jarrah (Eucalyptus marginata) forests and woodlands, on lateritic soils. It also occurs in low scrub, coastal dunes, heathlands, and woodlands — a broader ecological range than is sometimes appreciated. The distribution has been correlated with sites of long-term Aboriginal habitation, near lakes, springs, and freshwater points at granitic outcrops of the kwongan, suggesting that human management and seed dispersal may have influenced the species’ range over millennia.
Climate in the native range:
| Parameter | Southwestern WA (Dwellingup–Albany) |
|---|---|
| Mean annual temperature | 14–18 °C |
| Mean winter minimum | 5–10 °C |
| Historical absolute minimum | −2 to −4 °C (frost regular in inland jarrah forest) |
| Mean summer maximum | 25–33 °C |
| Annual rainfall | 600–1,200 mm (strongly winter-dominant, Mediterranean) |
| Köppen classification | Csb (warm-summer Mediterranean) to Csa (hot-summer Mediterranean) |
This is a Mediterranean climate with wet winters and dry summers — one of the world’s biodiversity hotspots. The species is adapted to summer drought, winter rainfall, and regular fire.
Conservation
Macrozamia riedlei is listed as Least Concern (LC) on the IUCN Red List (Bösenberg 2010), with a large and stable population estimated at 100,000–120,000 mature individuals. The species is not currently threatened at a population level.
However, habitat fragmentation through agricultural and residential land clearing is progressively isolating populations, which may restrict the long-distance seed dispersal (by emus) required for healthy gene flow. In the Perth metropolitan area and surrounding agricultural districts, the loss of jarrah forest habitat to urbanisation is an ongoing concern.
Aboriginal Ethnobotany
The cultural significance of Macrozamia riedlei to the Noongar people of southwestern Australia is immense — and archaeologically documented to a depth of time that is extraordinary.
Mordak — the processing method: the ripe but toxic seeds (known as pauyin) are harvested toward the end of March (after the austral summer). The Noongar detoxification process — called mordak — involves burying the seeds in pits, soaking, fermenting, and repeatedly leaching to remove the water-soluble toxins (cycasin, macrozamin). An excavation at a cave in Cape Le Grand National Park uncovered a nearly intact mordak pit dated to approximately 13,000 years ago — placing this food-processing technology deep in the Pleistocene.
The result is a starch-rich, calorie-dense food that sustained Noongar communities across the southwest for millennia. Different parts of the plant served different purposes: the fibrous leaves for weaving; the starchy pith of the trunk processed into a form of sago; the seeds as the primary product.
European encounters: the first recorded European poisonings from the zamia are among the earliest for any Western Australian plant — Vlaming (1697), La Pérouse (1788), Flinders (1801), and Sir George Grey (1839) all reported illness from eating the seeds unprepared. The settlers called the resulting cattle poisoning “wobbles” or “rickets” — paralysis of the hindquarters followed by death — and attempted to eradicate the plant wherever cattle grazed.
The Catholic Church in Western Australia has traditionally substituted Macrozamia riedlei fronds for palm fronds on Palm Sunday — a small but charming cultural footnote linking an ancient Australian cycad to Mediterranean Christian liturgy.
Seed Dispersal
The large, brightly coloured seeds of Macrozamia riedlei are dispersed primarily by the emu (Dromaius novaehollandiae), which is considered the primary long-distance dispersal agent. The large body size of the emu allows it to swallow the fleshy sarcotesta and pass or discard the hard inner seed at a distance from the parent plant. Other recorded seed consumers include the western rosella (Platycercus icterotis), common bronzewing pigeon (Phaps chalcoptera), white-tailed black cockatoo, silvereye, grey butcherbird, raven, western grey kangaroo, western brush wallaby, quokka (Setonix brachyurus), common brushtail possum, and western quoll (Dasyurus geoffroii).
The reliance on emus for long-distance dispersal raises conservation concerns: in fragmented landscapes where emus have been excluded (urban areas, fenced agricultural land), the capacity for gene flow between populations is severely reduced.
Fire Ecology
Like Macrozamia communis in eastern Australia, Macrozamia riedlei is strongly fire-adapted. The bole is buried underground, protecting the meristem from even intense fires. The coralloid roots are also deeply buried. After fire, the plant rapidly regenerates new leaves from the protected growing point. Dense stands of Macrozamia were noted by early colonial observers as especially prominent after fire — the species’ reproductive cycle, like that of many Australian plants, is stimulated by burning.
Pollination
Macrozamia riedlei is thought to be pollinated by a combination of wind and weevils — though the exact insect species and the relative importance of wind vs. insect vectors are less well characterised than for the eastern Australian Macrozamia species (where the roles of Tranes weevils and Cycadothrips thrips have been experimentally quantified). The plant uses pheromones and food rewards to attract and repel insect visitors between male and female cones — the same “push-pull” mechanism documented across the genus.
Cultivation
| Hardiness | −2 to −4 °C (28 to 25 °F) / USDA zones 9b–11 |
| Light | Full sun to partial shade |
| Soil | Well-drained; lateritic, sandy, sandy loam; acidic to neutral |
| Watering | Drought-tolerant; adapted to dry summers |
| Adult size | Rosette 0.5–2 m; trunk to 2 m in old specimens |
| Growth rate | Slow |
| Difficulty | 2/5 |
Macrozamia riedlei is an easy, hardy, and versatile cycad for cultivation. It is well suited to Mediterranean, warm-temperate, and subtropical climates. The species responds well to general fertilizer applications, favours full sun or partial shade, and tolerates a wide range of soil conditions provided drainage is adequate.
Light: full sun to partial shade. In habitat it grows as an understorey plant in jarrah forest, but cultivated specimens adapt well to full exposure.
Soil: well-drained is the only requirement. The native habitat is lateritic soils — acidic, iron-rich, and nutrient-poor. In cultivation, sandy or sandy loam soils work well. The nitrogen-fixing coralloid root symbiosis allows the species to thrive on very poor soils.
Watering: strongly drought-tolerant — adapted to the dry-summer Mediterranean climate of southwestern Australia. In cultivation, water during the growing season but allow the soil to dry between waterings. Overwatering and poor drainage are the main risks.
Cold hardiness: moderately frost-tolerant. The native range includes inland jarrah forest areas where frost is regular, with winter minima of −2 to −4 °C. USDA zone 9b minimum for permanent outdoor planting, with a half-zone safety margin applied as standard. In European Mediterranean climates (Côte d’Azur, coastal Var, Liguria), the species is suitable for sheltered positions. In areas prone to occasional severe winters (such as the events of 1956, 1985, or 2012 in France), winter protection — mulching the root zone, wrapping the crown with horticultural fleece — is advisable for established specimens.
Container culture: excellent — the species is one of the best cycads for containers, well suited to patios, courtyards, indoor culture, and even bonsai. Its slow growth, compact habit, and tolerance of low light and temperature make it a superb indoor plant that survives occasional neglect.
Buying Advice
Availability: Macrozamia riedlei is widely available from specialist cycad nurseries and general native plant nurseries in Australia, and from international dealers. Seeds are commonly offered. Prices are moderate. Be aware of the historical confusion with Macrozamia fraseri: plants labelled “M. riedlei” from the Swan Coastal Plain (Perth area) may actually be M. fraseri.
Propagation
Seed: the standard method. Clean the red sarcotesta (wear gloves — toxic) and sow in well-drained mix at 25–30 °C. Germination is cryptocotylar, typically within 6–12 months. No pretreatment required. Seedling growth is slow.
Offsets: occasionally produced; can be detached and potted.
Pests and Diseases
Scale insects and mealybugs: the most common pests. Manageable with horticultural oil.
Root rot: in waterlogged soils — particularly problematic given the species’ adaptation to well-drained lateritic substrates.
Toxicity: all parts are highly toxic, containing cycasin and macrozamin produced by the symbiotic cyanobacteria in the coralloid roots. The seeds are the most dangerous part. Toxic to dogs, cats, and livestock — the species is the source of the historical “wobbles” (zamia staggers) in cattle. The toxic roots have been used as rat poison. Never consume any part without thorough, traditional detoxification knowledge.
Landscape Use
Macrozamia riedlei is a supremely versatile landscape plant for warm, dry climates. Its compact, trunkless rosette of glossy dark green fronds — resembling a cross between a palm and a fern — creates a prehistoric, architectural accent in any garden setting. Use it as a specimen plant in a rockery, as understorey planting beneath eucalypts or other native trees (mirroring its natural habitat), in mass plantings on slopes for a dramatic primeval effect, as a container plant on a patio or courtyard, or as a beachside planting in coastal gardens. It pairs beautifully with other southwestern Australian natives — banksias, grevilleas, kangaroo paws, grass trees (Xanthorrhoea) — creating a quintessentially Australian landscape of extraordinary age and character. For gardeners in Mediterranean climates, this is one of the most rewarding and culturally resonant cycads available.
Frequently Asked Questions
How do I tell Macrozamia riedlei from Macrozamia fraseri?
Check the leaf cross-section: M. riedlei has flat or slightly keeled leaves; M. fraseri has distinctly keeled (V-shaped) leaves and larger cones. Geography is also diagnostic: they do not co-occur. M. riedlei is a jarrah forest species (Perth Hills southward); M. fraseri grows on the Swan Coastal Plain (Perth and coastal lowlands).
Can I eat the seeds?
Not without the Noongar traditional processing method (mordak), which involves prolonged burial, soaking, and leaching over days or weeks to remove the toxic cycasin and macrozamin. Raw seeds are acutely poisonous — the first recorded European poisonings in Western Australia date to Vlaming’s expedition in 1697. Do not attempt to process the seeds without expert knowledge.
Is Macrozamia riedlei suitable for Mediterranean climates in Europe?
Yes — this species is naturally adapted to a Mediterranean climate (wet winters, dry summers, 600–1,200 mm rainfall). It is well suited to the Côte d’Azur, Liguria, and similar zones. USDA zone 9b minimum for permanent outdoor planting. In areas prone to occasional severe winters, provide winter protection (fleece, mulching) for established specimens — a plant that has taken decades to grow is not worth losing to a single cold event.
Why are the zamias associated with cattle poisoning?
The leaves and seeds contain cycasin and macrozamin, produced by nitrogen-fixing cyanobacteria in the roots. Cattle that graze on the plants develop “wobbles” (zamia staggers) — progressive hindquarter paralysis leading to death. This led early settlers to attempt eradication of the plant in grazing areas.
Authority Websites and Databases
POWO — Plants of the World Online (Kew)
https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:297147-1
The accepted nomenclatural record. Basionym: Cycas riedlei Fisch.
FloraBase — Western Australian Herbarium
https://florabase.dbca.wa.gov.au/browse/profile/85
Official WA Flora profile: tree or cycad, 0.5–3 m, usually trunkless, lateritic soils, jarrah forests, flowering September–October. Bioregions: Esperance Plains, Jarrah Forest, Swan Coastal Plain, Warren.
LLIFLE Encyclopedia
https://llifle.com/Encyclopedia/PALMS_AND_CYCADS/…
Comprehensive profile: distribution (Dwellingup to Albany, 100,000–120,000 mature individuals), morphology (12–30 leaves, 1–2.2 m, flat to slightly keeled, leaflets 23–48 cm), cones (male 29–41 cm, female 25–35 cm), fire ecology (bole and coralloid roots buried, regeneration after fire), ethnobotanical uses, cultivation.
Wikipedia — Macrozamia riedlei
https://en.wikipedia.org/wiki/Macrozamia_riedlei
Detailed account of Noongar ethnobotany (mordak processing, pauyin harvest, Cape Le Grand 13,000-year-old pit), seed dispersal ecology (emu as primary vector, cockatoos, possums, quoll), Palm Sunday frond substitution, “wobbles” cattle poisoning, colonial poisoning records (Vlaming 1697 to Grey 1839).
The Wetlands Centre — Flora in Focus: Zamia
https://www.thewetlandscentre.org.au/blog/zamia/
Noongar cultural significance (jeeriji), Anselme Riedlé etymology, confusion with M. fraseri, dioecious reproduction, pollination by combination of wind and weevils.
Anthropology from the Shed — Macrozamia: the fermented oil fruit
https://www.anthropologyfromtheshed.com/…
Detailed ethnobotanical reconstruction of Noongar sarcotesta processing methods. Distinction between M. riedlei (jarrah forest, flat leaves, smaller cones) and M. fraseri (coastal plain, keeled leaves, larger cones) following Ken Hill’s revision. Historical colonial accounts of cone weight (18–22 kg per Von Huegel 1833).
Bibliography
Barrett, R. L., & Tay, E. P. (2016). Perth Plants: A Field Guide to the Bushland and Coastal Flora of Kings Park and Bold Park (2nd ed.). CSIRO Publishing.
Bösenberg, J. D. (2010). Macrozamia riedlei. The IUCN Red List of Threatened Species 2010.
Gardner, C. A. (1930). Enumeratio Plantarum Australiae Occidentalis, 3.
Gerlach, M. (2012). The population structure and dynamics of Macrozamia riedlei within the Perth region. Honours thesis, Murdoch University.
Hill, K. D. (1998). Cycadophyta. Flora of Australia, 48, 597–661.
Jones, D. L. (2002). Cycads of the World (2nd ed.). New Holland Publishers, Sydney.
Whitelock, L. M. (2002). The Cycads. Timber Press, Portland.
Wrigley, J. W., & Fagg, M. (2003). Australian Native Plants (5th ed.). Reed New Holland.