Queensland farmers call it the “Twisted Ricketts Weed” — a name that captures both the most obvious physical feature of the plant (the violently spiralling fronds) and the paralysis it inflicts on cattle that eat the young leaves. Cycad collectors, seeing past the vernacular contempt, call it the Pineapple Zamia — for the small, pineapple-like cones that emerge from the centre of the twisted crown. Botanists call it Macrozamia pauli-guilielmi and list it as Endangered under both Queensland and Australian federal legislation. It is one of five Macrozamia species characterised by strongly spirally twisted leaves with narrow, deeply concave leaflets, and it is separated from the others by its very narrow (2–4 mm), pale green, dull leaflets that are yellowish beneath. A single metre-long frond can twist ten complete 360° rotations — a degree of rachis spiralling unmatched in the genus. Endemic to the Wide Bay district of southeastern Queensland, between the Isis River and Wolvi, it grows in lowland wallum — the banksia and eucalypt-dominated heath and open forest on stabilised sand dunes that was once widespread along the Queensland coast and is now fragmented by coastal development, pine plantations, and agriculture.
Described by Walter Hill and Ferdinand von Mueller in 1859, it belongs to the genus Macrozamia — the largest exclusively Australian cycad genus, with around 40 species — and within that genus it is part of the M. pauli-guilielmi complex, a group of closely related and potentially overlapping species (M. parcifolia, M. lomandroides) whose boundaries remain imperfectly resolved.
Quick Facts
| Scientific name | Macrozamia pauli-guilielmi W.Hill & F.Muell. |
| Family | Zamiaceae |
| Origin | Wide Bay district, SE Queensland, Australia |
| Adult size | Acaulescent; caudex subterranean (~25 × 20 cm); 1–6 leaves, 50–100 cm long |
| Hardiness | −1 to −2 °C (30 to 28 °F) / USDA zones 10a–11 |
| IUCN | Endangered (EN) — also Endangered under QLD and EPBC Acts |
| CITES | Appendix II (all cycads) |
| Cultivation difficulty | 3/5 |
Taxonomy and Nomenclature
Macrozamia pauli-guilielmi was described by Walter Hill (Director of the Brisbane Botanic Gardens) and Ferdinand von Mueller in 1859 in Mueller’s Fragmenta Phytographiae Australiae (1(4): 86). It is one of the earliest Macrozamia species described from Queensland.
Etymology: the specific epithet pauli-guilielmi is a Latinisation of the name Paul Wilhelm — honouring Duke Paul Wilhelm of Württemberg (1797–1860), a German naturalist and explorer who supported botanical exploration in Australia.
The M. pauli-guilielmi complex: the species is part of a complex including Macrozamia parcifolia and Macrozamia lomandroides. Systematic and genetic studies are required to determine accurate species boundaries (Queensland Herbarium 2007). Allozyme analysis has shown M. parcifolia and M. pauli-guilielmi to be genetically more similar to each other than either is to M. crassifolia — supporting the morphological groupings. The species was previously confused with M. lomandroides (which grows in similar terrain) until David Jones recognised the differences and described M. lomandroides as distinct.
Section: Parazamia — the small, subterranean-caudex, often twisted-leaf group.
Synonyms: Encephalartos pauli-guilielmi (W.Hill & F.Muell.) F.Muell.; Macrozamia spiralis var. cylindracea Benth.; Macrozamia tenuifolia Miq.; Zamia mackenii Miq.
Common names: Pineapple Zamia; Pineapple Cycad. Local farming name: “Twisted Ricketts Weed.”
Morphological Description
Macrozamia pauli-guilielmi is a small, dioecious, evergreen cycad of section Parazamia — compact, ground-hugging, and extraordinary in its leaf morphology.
Caudex: entirely subterranean, non-branching, approximately 25 cm long and 20 cm in diameter. Below ground, the plant has 13 parsnip-like roots — a distinctive underground architecture.
Leaves: 1–6 per crown (up to 12 in some descriptions), forming a sparse, erect crown. Mature leaves are 50–100 cm long, hairless except for the wool at the base. The petiole is broad at the base (~2 cm), flattened (5–15 cm long), keeled on one side and flat on the other.
The diagnostic character — extreme rachis twist: the rachis is very strongly spirally twisted — twisting approximately every 7.5 cm (3 inches), such that a one-metre frond can execute ten complete 360° rotations. This is the most intensely twisted rachis of any Macrozamia species and gives the plant its unmistakable appearance.
Leaflets: 140–200 per leaf (50–200 in broader descriptions), 15–40 cm long and 2–4 mm wide — very narrow, thick-textured, dark green and dull above, yellowish beneath, spreading to weeping in the upper half. Leaflet bases are white and conspicuously thickened. The narrowness of the leaflets, combined with the extreme twist, gives the frond an airy, ornamental quality. Some leaflets may have 2–3 apical teeth.
Cones: small, somewhat pineapple-like — the source of the common name.
- Male cones: cylindrical, 8–14 cm long, 3.5–5 cm diameter (up to 25 cm in broader descriptions).
- Female cones: ovoid, 9–12 cm long, 5–6.5 cm diameter (up to 25 cm). Longest sporophyll spines 1.5–4 cm.
Coning frequency: extremely irregular — every 4–6 years. Coning often follows fire (masting), with a small percentage of individuals coning in the first year post-fire and a high percentage in the second year. Cones may not be produced at all in unfavourable years. Female cones are receptive to pollinators in November; seed ripens in March–April. Due to the delayed fertilisation unique to cycads, seeds are not ready to germinate for a further 12 months.
Seeds: 1.7–2.5 cm long, 1.3–2 cm diameter, red (or orange to scarlet) when ripe. Highly toxic.
Pollinator: not confirmed, but likely a species of Tranes weevil (Queensland Herbarium 2007). Male cones release volatile fragrances to attract pollinators.
Similar Species and Common Confusions
| Character | Macrozamia pauli-guilielmi | Macrozamia flexuosa | Macrozamia parcifolia | Macrozamia lomandroides |
|---|---|---|---|---|
| Leaflet width | 2–4 mm (narrowest) | Broader | Variable | Variable (Lomandra-like) |
| Leaflet colour | Pale green, dull, yellowish beneath | Green | Variable | Variable |
| Petiole | Strongly flattened, short (5–15 cm) | Less flattened | Variable | Variable |
| Rachis twist intensity | ~10 × 360° per metre (extreme) | Multi-twisted | Twisted | Twisted |
| Distribution | Wide Bay district (QLD) | Central coast NSW | QLD | QLD |
| Conservation | Endangered | Vulnerable | Endangered | Endangered |
Macrozamia pauli-guilielmi is morphologically closest to M. flexuosa (from the NSW central coast) but is distinguished by its shorter, more flattened petioles and narrower, lighter green, dull leaflets that are yellowish beneath. Within the M. pauli-guilielmi complex, PACSOA notes that M. lomandroides was long confused with M. pauli-guilielmi due to similarities in caudex, rachis twist, and toning — but the rachis shape differs.
Distribution and Natural Habitat
Macrozamia pauli-guilielmi is endemic to the Wide Bay district of southeastern Queensland, between the Isis River and Wolvi. This places it in the coastal hinterland northwest of the Sunshine Coast and south of Bundaberg — the Burnett Mary NRM region.
The species grows in lowland wallum — open forest or woodland dominated by Banksia or eucalypts, or in shrubland or heath, generally on stabilised sand dunes at altitudes of 5–230 m. It has no preferred aspect. The wallum habitat is fire-prone and burns irregularly at intervals of two years or longer — fires can be intense, uncontrolled, and started by lightning or adjacent land management.
Climate in the native range:
| Parameter | Wide Bay district (SE QLD coast) |
|---|---|
| Mean annual temperature | 20–22 °C |
| Mean winter minimum | 8–12 °C |
| Frost | Rare to absent on the coast; occasional inland |
| Mean summer maximum | 28–32 °C |
| Annual rainfall | 900–1,200 mm (summer-dominant) |
| Köppen classification | Cfa (humid subtropical) |
This is a warm subtropical, frost-free coastal climate — the species has virtually no natural exposure to freezing temperatures.
Conservation
Macrozamia pauli-guilielmi is listed as Endangered under the Queensland Nature Conservation Act, the Australian EPBC Act, and the IUCN Red List. It is included in the National Multi-species Recovery Plan for the cycads (Queensland Herbarium 2007) alongside Cycas megacarpa, Cycas ophiolitica, Macrozamia cranei, Macrozamia lomandroides, and Macrozamia platyrhachis — a plan that reflects the disproportionate number of threatened cycads in Queensland.
Threats:
- Habitat loss: the wallum habitat on which M. pauli-guilielmi depends has been extensively cleared for pine plantations, agriculture, and coastal development. What remains is fragmented.
- Seed and plant poaching: PACSOA and the Australian Government identify heavy illegal collecting as a major threat. The species’ ornamental qualities (compact size, twisted fronds, pineapple-like cones) make it a target for cycad collectors. Proximity to roads increases poaching risk.
- Fire: the wallum habitat is extremely fire-prone. Fires kill seedlings and unburied seeds, and may destroy pollinator populations. While adult plants resprout from the subterranean caudex, the irregular coning cycle (4–6 years) means that a fire during a coning year can destroy an entire cohort of seeds.
- Cattle poisoning retaliation: the species causes “rickets” (hindquarter paralysis) in cattle, leading farmers to destroy plants on pastoral land.
The species is listed as a “Back on Track” critical priority plant species for the Burnett Mary NRM region and a locally significant species in the Fraser Coast Region Threatened Species Action Plan.
Cultivation
| Hardiness | −1 to −2 °C (30 to 28 °F) / USDA zones 10a–11 |
| Light | Full sun to partial shade |
| Soil | Well-drained; sandy (wallum-type substrate ideal) |
| Watering | Regular; moderate drought tolerance once established |
| Adult size | Compact: 50–100 cm fronds, sparse crown of 1–6 leaves |
| Growth rate | Slow (but faster in cultivation than reported field estimates suggest) |
| Difficulty | 3/5 |
Despite its Endangered status in the wild, Macrozamia pauli-guilielmi is a rewarding species in cultivation. PACSOA rates it highly: “as a collector’s plant M. pauli-guilielmi has better symmetry and eye appeal and, I think, rates at least as high as Bowenia serrulata and many of the exotic diminutive zamias as a potted plant for cultivation.” This endorsement from an experienced Australian grower places it among the best section Parazamia species for container culture.
Light: full sun to partial shade. In habitat it grows in open wallum — full sun is natural.
Soil: well-drained, sandy — mirroring the stabilised sand dune substrate of the native habitat. The species is likely intolerant of heavy or waterlogged soils.
Watering: regular during the growing season. The native range receives 900–1,200 mm of summer-dominant rainfall — not drought-adapted.
Cold hardiness: strictly tropical-subtropical — the species has essentially no natural frost exposure. USDA zone 10a minimum. In European Mediterranean climates, this is a container plant only — to be brought under cover in winter. Even in zone 10a, winter protection is advisable. This is not a species for outdoor planting in any frost-prone climate.
Container culture: the ideal use for this species outside the tropics. The compact size, the sparse but spectacularly twisted fronds, and the pineapple-like cones make it a superb conversation piece in a pot on a terrace, in a conservatory, or on a bright windowsill. The slow growth means it stays in proportion for years. Bring indoors or under cover at the first sign of cold weather.
Buying Advice
Availability: Macrozamia pauli-guilielmi is rare in cultivation and extremely difficult to obtain legally. The Endangered status means that wild collection is prohibited, and nursery-propagated plants are uncommon. Seeds occasionally appear from specialist Australian cycad nurseries. Never purchase plants or seeds of uncertain provenance — illegal collection is identified as a major threat to this species, and purchasing illegally collected material directly undermines conservation.
Propagation
Seed: the only method. Clean the red sarcotesta (gloves — toxic). Sow in well-drained sandy mix at 25–30 °C. Note: due to the delayed fertilisation unique to cycads, fresh seed is not ready to germinate for approximately 12 months after ripening. Patience is essential. Growth is slow but reportedly faster in cultivation than in the field.
Pests and Diseases
Scale insects: the most common pest. Manageable with horticultural oil.
Root rot: in heavy or waterlogged soils.
Toxicity: all parts are highly toxic. The species causes “rickets” (hindquarter paralysis) in cattle, particularly from the young leaves in spring. Indigenous Australians reportedly stored the seeds for use as food, but the toxicity and long-term health risks mean this practice has long been abandoned (Queensland Herbarium 2007). Toxic to dogs, cats, livestock, and humans.
Landscape Use
Macrozamia pauli-guilielmi is a collector’s cycad — small, rare, endangered, and visually extraordinary. The intensely twisted fronds (ten 360° rotations per metre), the very narrow pale green leaflets weeping from the spiralling rachis, and the pineapple-like cones create a plant of singular aesthetic quality. In a collection of section Parazamia species, it is the centrepiece — the species that stops visitors and demands explanation. Use it as a premium container specimen on a bright terrace, in a cycad conservatory, or as part of a curated collection of Queensland’s threatened cycad flora (alongside M. lomandroides, M. cranei, M. platyrhachis). The sparse crown (1–6 leaves) means it works best as a single-specimen display where the individual frond structure can be fully appreciated. For the grower who values rarity, conservation significance, and morphological uniqueness over landscape scale, there is no better Macrozamia than this one.
Frequently Asked Questions
Why is it called the “Pineapple Zamia”?
The female cones are small, ovoid, and somewhat pineapple-shaped — a visual resemblance that is more pronounced in this species than in most other Macrozamia.
Why is it Endangered?
Habitat loss (wallum clearing for development, pine plantations, agriculture), illegal collection of plants and seeds, fire destroying seedlings and seeds, and destruction by farmers (due to cattle poisoning). The species is endemic to a small area of the Wide Bay district and has no large, secure population.
Can I grow it outdoors in Europe?
No — this is a strictly subtropical species with no frost tolerance. USDA zone 10a minimum. In European climates, it is a container/conservatory plant only. Bring indoors in winter.
How does it relate to Macrozamia flexuosa?
Morphologically closest — both have strongly twisted leaves. M. pauli-guilielmi is distinguished by its shorter, more flattened petioles, and narrower, lighter, duller leaflets that are yellowish beneath. M. flexuosa is from the NSW central coast (different state, different climate).
Authority Websites and Databases
POWO — Plants of the World Online (Kew)
https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:297191-1
Accepted species. First published in Fragm. (Mueller) 1(4): 86 (1859).
Australian Government — SPRAT Database
https://www.environment.gov.au/cgi-bin/sprat/…
Endangered under EPBC Act. Species complex with M. parcifolia and M. lomandroides. Five species of strongly twisted-leaf Macrozamia; separated by very narrow, pale green, dull leaflets. Lowland wallum habitat on stabilised sand dunes, 5–230 m. Fire-stimulated masting. 13 parsnip-like roots. Threats: habitat loss, poaching, fire, cattle poisoning retaliation.
QLD Government — Species Profile
https://apps.des.qld.gov.au/species-search/details/?id=16708
Endangered (QLD). Underground stem to 20 cm diameter, 1–6 erect leaves, 50–100 cm, strongly spiral rachis, 140–200 leaflets 2–4 mm wide, dull dark green above, yellowish beneath. Male cones 8–14 cm, female 9–12 cm. Coning every 4–6 years. Seeds ripe March–April, 12-month germination delay.
PACSOA — Palm and Cycad Societies of Australia
https://pacsoa.org.au/wiki/index.php/Macrozamia_pauli-guilielmi
2–5 erect leaves, rachis twisted every 7.5 cm (~10 × 360° per metre). Petiole broad, keeled/flat. “Twisted Ricketts Weed.” Confused with M. lomandroides until Jones’ revision. “As a collector’s plant, rates at least as high as Bowenia serrulata and many exotic diminutive zamias.” Best in containers.
Queensland Herbarium (2007) — National Multi-species Recovery Plan
https://www.environment.gov.au/biodiversity/…
Recovery plan covering six threatened cycads including M. pauli-guilielmi. Threats, management actions, research needs. Species boundaries within the M. pauli-guilielmi complex require systematic and genetic studies.
Bibliography
Hill, K. D. (1998). Cycadophyta. Flora of Australia, 48, 597–661.
Hill, W., & Mueller, F. von (1859). Macrozamia pauli-guilielmi. Fragmenta Phytographiae Australiae, 1(4), 86.
Jones, D. L. (2002). Cycads of the World (2nd ed.). New Holland Publishers, Sydney.
Jones, D. L., & Forster, P. I. (1994). Seven new species of Macrozamia section Parazamia (Zamiaceae) from Queensland. Austrobaileya, 4, 269–288.
Queensland Herbarium (2007). National Multi-species Recovery Plan for the cycads, Cycas megacarpa, Cycas ophiolitica, Macrozamia cranei, Macrozamia lomandroides, Macrozamia pauli-guilielmi and Macrozamia platyrhachis. Environmental Protection Agency, Brisbane.
Whitelock, L. M. (2002). The Cycads. Timber Press, Portland.