Macrozamia machinii

Macrozamia machinii is a small cycad with no visible trunk from southern Queensland, in eastern Australia, confined to the Inglewood district on the Darling Downs, where it grows in clumps in open forest on deep sand. This species of the genus Macrozamia is known to biologists for its pollinator, a small weevil of the genus Tranes whose efficiency was measured in the field and the laboratory in 2005. Known for a time only under an informal name, and later treated as a form of Macrozamia plurinervia, it is now accepted as a species and listed as Vulnerable.

Key facts about Macrozamia machinii

  • Accepted name: Macrozamia machinii P.I.Forst. & D.L.Jones (1994), accepted by The World List of Cycads (version 2026.08.15) and the Australian Plant Census
  • Former names and synonyms: no synonym; before its description, the informal name Macrozamia sp. (Inglewood C.T.White AQ142073); treated by the Flora of Australia (1998) as a synonym of Macrozamia plurinervia
  • Family: Zamiaceae, order Cycadales; section Parazamia, Macrozamia plurinervia complex
  • Common names: no specific name attested in English or in any other language
  • Natural range: southern Queensland, Australia: at least eight populations near Inglewood, from the Wondul Range to Limevale; 320 to 460 m above sea level
  • IUCN status: Vulnerable (VU B1ab(iii,v)+2ab(iii,v)), assessment by J.D. Bösenberg dated 14 August 2020 and published in 2022
  • CITES and other protection: CITES Appendix II (annotation #4); Annex B in the European Union; Vulnerable under the federal EPBC Act and under Queensland law
  • Documented hardiness: no cultivation data; −2.7 °C (27.1 °F) was the lowest temperature at the Inglewood Forest station from 2000 to 2013 (see Cold hardiness)
  • Light and soil: in the wild, open forest on flat ground with deep sand, more rarely a lateritic ridge
  • Habit and adult size: underground stem 20 to 30 cm across, branching into clumps of up to 10 heads; 1 to 8 leaves 60 to 90 cm long
  • In the UK, US and Australia: Royal Botanic Garden Sydney (plants of wild origin received in 2022); Montgomery Botanical Center in Florida (accessions of 2023, see below); no British garden
  • Toxicity: not documented for the species; seeds and leaves toxic throughout the genus (see Toxicity and precautions)

How to recognise Macrozamia machinii

Macrozamia machinii is recognised by its clumps of spirally twisted leaves and its thick leaflets, dark green and dull on both faces, whose yellow, orange or reddish base often colours the leaf axis. The original description (Jones and Forster, 1994) gives the following characters.

  • Stem: underground, more or less ovoid, 20 to 30 cm across, branching, with up to 10 heads in a clump.
  • Leaves: 1 to 8 in the crown, 60 to 90 cm long, dark green, dull, erect; young leaves silky; expanded base densely covered with soft grey wool; petiole 13 to 21 cm long; axis green to yellow-green, twisted two to six times.
  • Leaflets: 80 to 140 per leaf, linear, 8 to 32 cm long and 2.5 to 10 mm wide, thick, dark green and dull on both faces, channelled above; callous base yellow to orange or reddish, the colour often extending along the margin of the axis between the leaflets; the lowest leaflets do not become spines.
  • Male cones: more or less cylindrical, 8 to 20 cm long and 4 to 6 cm across; the upper scales carry a stiff spine up to 1.4 cm long.
  • Female cones: ovoid to ovoid-cylindrical, 8 to 18 cm long and 5 to 7 cm across, erect, green to glaucous, on a stalk 15 to 25 cm long; the longest spines about 2 cm.
  • Seeds: oblong to ovoid, 2 to 2.5 cm long and 2 to 2.3 cm wide, with orange to red flesh.

Hybrids

No hybrid involving Macrozamia machinii has been documented, in the wild or in cultivation.

Possible confusion

The main confusion is with Macrozamia plurinervia, a species of New South Wales and the far south of Queensland, under whose name Macrozamia machinii has sometimes been placed. According to Jones and Forster (1994), it differs by its thicker leaflets, dark green and dull on both faces (grey-green to glaucous in Macrozamia plurinervia), by its smaller cones and by its smaller, oblong to ovoid seeds (broadly ovoid to oblong-ellipsoid in Macrozamia plurinervia). The two species also occupy different habitats: Macrozamia plurinervia grows in hilly country with large granite outcrops and gravelly loam soils, Macrozamia machinii on flat plains and breakaways in deep sand.

The other small species of the Darling Downs, such as Macrozamia occidua, near Sundown, or Macrozamia viridis, live in other districts; on the Darling Downs, the origin of a plant is a strong clue to its identity.

Taxonomy

Macrozamia machinii P.I.Forst. & D.L.Jones is accepted by The World List of Cycads and the Australian Plant Census. Paul I. Forster and David L. Jones described it in 1994 in the journal Austrobaileya (vol. 4, no. 2, pp. 276–277), in a paper describing seven new species of section Parazamia from Queensland. The type, a male plant, was collected near Inglewood on 11 April 1992 by P.I. Forster and P. Machin (no. 9767B); the holotype is held in Brisbane (BRI), with an isotype in Canberra (CBG).

Section Parazamia brings together small species with an underground stem, usually twisted leaves, no spiny leaflets and no mucilage canals. Jones and Forster placed Macrozamia machinii in the complex of Macrozamia plurinervia. The Flora of Australia (Hill, 1998) then treated it as a mere synonym of Macrozamia plurinervia, a position no longer followed: The World List of Cycads and the online Flora of Australia, whose profile of the species was published on 14 April 2026, accept it as a distinct species.

Etymology and history

The species honours Peter J. Machin, a technical assistant at the Queensland Herbarium in Brisbane, “whose unstinting enthusiasm and interest in the cycads has been catalytic in this work progressing so rapidly” (Jones and Forster, 1994). The genus name Macrozamia combines the Greek makros, “large”, with the genus name Zamia.

Its story is one of rediscovery: according to the authors, the plant appears to have been first collected in November 1922 by the botanist C.T. White, but it was not found again until 1991, by Peter Machin himself.

Common names

No specific common name is attested in English, and no Aboriginal name is recorded; WildNet, the Queensland Government’s wildlife database, gives none. Gardeners and nurseries use the scientific name.

In the wild

Macrozamia machinii is known from at least eight populations near Inglewood, on the Darling Downs, in south-eastern Queensland (Jones and Forster, 1994); WildNet places its range between the Wondul Range and Limevale. Most populations grow on sandy soils on flat ground, in open forest dominated by Angophora leiocarpa, Allocasuarina inophloia, Callitris glaucophylla, Lysicarpus angustifolius and Acacia conferta. One population occupies a red lateritic ridge, with Callitris endlicheri, Eucalyptus panda and Eucalyptus apothalassica. The populations lie at 320 to 460 m.

The cones mature from September to December and the seeds ripen from February to April. According to WildNet, after Halford (1997), the plants may not cone every year when conditions are unfavourable.

A weevil pollinator

Macrozamia machinii is pollinated by a specialised weevil of the genus Tranes, in an obligate mutualism. The relationship was measured by Irene Terry and her colleagues Walter, Donaldson, Snow, Forster and Machin in a paper published in 2005 in the American Journal of Botany, which compared this weevil with the thrips Cycadothrips chadwicki, pollinator of Macrozamia lucida.

Their field and laboratory tests show that no seeds formed when both wind and insects were excluded from the female cones, whereas excluding wind-borne pollen alone did not prevent seed set, because the insects still reached the cone. In enclosures, each weevil pollinated an average of 26.2 ovules per cone, against 2.4 for each thrips. Fluorescent powders traced their movements: the thrips left the powder concentrated around the micropyle, the precise point where pollen must arrive, whereas the weevil scattered it over different parts of each ovule, leaving a greater role to chance. Each weevil delivered on average 6.2 pollen grains to each ovule it visited; in sum, the pollination potential of about 25 thrips approximates that of one weevil.

Another study by the same team, on the heat produced by the cones, specifies the timing. In Macrozamia machinii, the weevil moves after sunset, while the cone is heating, and the difference in heat production between male and female cones is much larger than in Macrozamia lucida: male cones reach higher metabolic peaks and female cones much lower ones (Roemer et al., 2005).

Conservation status and regulation

Macrozamia machinii is listed as Vulnerable (VU) on the IUCN Red List under criteria B1ab(iii,v)+2ab(iii,v), which point to a restricted range and a continuing decline in the quality of its habitat and in the number of mature plants. The assessment, by J.D. Bösenberg, is dated 14 August 2020 and was published in 2022 (The World List of Cycads, GBIF and Crossref, checked on 26 October 2026).

In Australia, it is listed as Vulnerable under the federal Environment Protection and Biodiversity Conservation Act 1999 (EPBC) and under the Queensland Nature Conservation Act; WildNet also records it as a restricted plant and a sensitive species (checked on 26 October 2026). Jones and Forster (1994) noted that most populations lie in state forests, but that the plants may be subject to poaching.

Like other Macrozamia, it has been listed in CITES Appendix II since 4 February 1977, with annotation #4: seeds and pollen are exempt, but plants are not. In the European Union it falls under Annex B of Regulation (EC) No 338/97, as amended by Regulation (EU) 2026/1383, applicable since 29 June 2026 (Species+, checked on 26 October 2026). Check the regulations in force before any purchase or import, and buy only plants whose cultivated origin is proven.

Growing Macrozamia machinii

No cultivation experience with Macrozamia machinii has been published. Its habitat gives a few pointers: deep, free-draining sand, open forest of Australian cypress pines (Callitris) and Angophora, and an inland climate with hot summers, modest rainfall (about 600 mm a year at Inglewood Forest) and light winter frosts. These are assumptions drawn from the wild, not tested advice.

Outdoor and in-ground cultivation

  • Light: in the wild, open forest; a bright position is a deduction from the habitat.
  • Soil: in the wild, deep sand, sometimes laterite; a very free-draining sandy mix is the logical choice.
  • Water: no published data; the habitat is fairly dry, with most rain in summer.
  • Space: a clump of several heads, with leaves up to 90 cm long.

Container cultivation

No container culture has been described. Its size suits a deep pot of sandy compost. A plant in a pot loses the protection that the soil gives to its underground stem in winter (see Cold hardiness).

In cultivation in the UK, US and Australia

  • Australia: the Royal Botanic Garden Sydney holds an accession of wild origin received in 2022 (S2022-0087), according to its Garden Explorer; it is the only Australian garden that declares the species to BGCI.
  • United States: the online catalogue of Montgomery Botanical Center, in Coral Gables (Florida), lists five accessions numbered in 2023 (20230276 to 20230280) under the entry Macrozamia plurinervia, with Macrozamia machinii given as the accepted name. Montgomery does not declare the species to BGCI under this name, and no other American garden does.
  • United Kingdom: no British garden declares it to BGCI (checked on 26 October 2026).

No grower in the English-speaking world has published a cultivation result.

Propagation

Macrozamia machinii is propagated by seed. Outside Australia, without its Tranes weevil, a female plant must be hand-pollinated with pollen from a male plant. Wear gloves to clean the seeds, whose flesh is toxic.

Pests and diseases

No pest or disease specific to Macrozamia machinii is documented. The main danger reported in the wild is poaching. For Macrozamia grown in Europe, growers’ forums mainly mention scale insects and rot in cold, wet soil (see the genus page).

Cold hardiness

The cold hardiness of Macrozamia machinii has not been tested in cultivation: no result has been published.

Mediterranean and European experience

No result has been published in Europe, in the ground or in a pot. In March 2014, on the French Fous de palmiers forum, a grower reported the opinion of an Australian specialist who placed Macrozamia machinii among the “least hardy” species, those of inland Queensland, the third of four groups. No temperature was given.

United Kingdom, United States and Australia

At the Inglewood Forest weather station (379 m), in the heart of the species’ range, the lowest temperature recorded from 2000 to 2013 is −2.7 °C (27.1 °F), on 19 July 2007; frost occurred on fewer than four days a year on average, the mean July minimum was 5.6 °C (42.1 °F), and the thermometer reached 42 °C (107.6 °F) in summer (Bureau of Meteorology). This short series, from a station now closed, does not necessarily cover the coldest winters. These figures describe the habitat, not the tolerance of the plant. In Britain and in the colder parts of the United States, a pot kept frost-free in winter is the prudent choice.

Toxicity and precautions

No toxicity data specific to Macrozamia machinii have been published, but the risk is well documented for the genus. Macrozamia contain toxic glycosides (cycasin, macrozamin), from which methylazoxymethanol is derived, a poison of the liver; cattle that eat the leaves can develop a locomotor disorder of the hind legs (Healy, 1967), which McKenzie (2006) describes as irreversible, ending in paralysis of the hindquarters, with no treatment.

Treat the plant as toxic: wear gloves to handle the seeds and keep them out of reach of children and animals. In case of ingestion, contact a poison centre, a doctor or a vet without delay.

Traditional uses

No traditional use specific to Macrozamia machinii is recorded. Other Macrozamia provided Aboriginal peoples with seeds that could be eaten after long processing (see the genus page); never eat cycad seeds.

Frequently asked questions

What pollinates Macrozamia machinii?

A weevil of the genus Tranes. Terry et al. (2005) showed that insects are needed for seed set and that a single weevil pollinates on average 26 ovules per cone, as many as about 25 thrips.

Why do its cones heat up?

Heat goes with pollination. The cones produce heat, and the weevil moves after sunset, while the cone is warming (Roemer et al., 2005).

How does it differ from Macrozamia plurinervia?

By its leaflets. Those of Macrozamia machinii are thicker and dull dark green on both faces, whereas those of Macrozamia plurinervia are grey-green to glaucous; its cones and seeds are also smaller.

Where does its name come from?

From Peter Machin, a technical assistant at the Queensland Herbarium. He found the species again in 1991, nearly seventy years after the first known collection.

How hardy is it?

Nobody knows. No trial has been published; its region has light frosts (−2.7 °C, or 27.1 °F, at Inglewood Forest from 2000 to 2013), and an Australian specialist ranks it among the less hardy species.

Is it poisonous?

Probably, like all cycads. No study deals with this species, but the seeds and leaves of Macrozamia are toxic to people and livestock.

Further reading on Succulentes

Sources

Reference sites

Bibliography

  • Jones, D.L. & Forster, P.I. (1994). Seven new species of Macrozamia section Parazamia (Miq.) Miq. (Zamiaceae section Parazamia) from Queensland. Austrobaileya 4(2): 269–288. [Protologue of Macrozamia machinii, pp. 276–278: description, type, habitat, phenology, etymology; full text.]
  • Terry, I., Walter, G.H., Donaldson, J.S., Snow, E., Forster, P.I. & Machin, P.J. (2005). Pollination of Australian Macrozamia cycads (Zamiaceae): effectiveness and behavior of specialist vectors in a dependent mutualism. American Journal of Botany 92(6): 931–940. doi:10.3732/ajb.92.6.931 [Peer-reviewed paper; abstract read on PubMed.]
  • Roemer, R., Terry, I., Chockley, C. & Jacobsen, J. (2005). Experimental evaluation and thermo-physical analysis of thermogenesis in male and female cycad cones. Oecologia 144(1): 88–97. doi:10.1007/s00442-005-0045-0 [Peer-reviewed paper; abstract read on PubMed.]
  • Hill, K.D. (1998). Cycadophyta. In: McCarthy, P.M. (ed.), Flora of Australia 48: 597–661, 717–719. ABRS/CSIRO Publishing, Melbourne. [Treatment of the species as a synonym of Macrozamia plurinervia, as stated in the online Flora of Australia.]
  • Bösenberg, J.D. (2022). Macrozamia machinii. The IUCN Red List of Threatened Species 2022: e.T178867A48868487. doi:10.2305/IUCN.UK.2022-1.RLTS.T178867A48868487.en [Vulnerable, criteria B1ab(iii,v)+2ab(iii,v); assessment dated 14 August 2020, from Crossref.]
  • Haynes, J.L. (2022). Etymological compendium of cycad names. Phytotaxa 550(1): 1–31. doi:10.11646/phytotaxa.550.1.1 [Etymology, as given by The World List of Cycads.]
  • Healy, P.J. (1967). Macrozamia poisoning. Institute of Inspectors of Stock of New South Wales Year Book. [Reprinted by Flock & Herd.]
  • McKenzie, R.A. (2006). Toxicology for Australian Veterinarians: cycads (Cycas, Macrozamia, Lepidozamia, Bowenia), pp. 282–288. Animal Health Australia, Australian Animal Pathology Standards Program (PDF): https://aapspextranet.animalhealthaustralia.com.au/wp-content/uploads/2019/04/tav7_17_unknowntoxins_pt2.pdf [Australian veterinary reference text; describes the cattle syndrome as irreversible, ending in paralysis of the hindquarters, with no treatment.]
  • Calonje, M., Stevenson, D.W. & Osborne, R. (2026). The World List of Cycads, version 2026.08.15. Montgomery Botanical Center, Coral Gables. doi:10.5281/zenodo.21958524 [Reference list.]