Macrozamia Miq. is Australia’s dominant cycad genus — approximately 41 species, all endemic to the Australian continent, ranging from compact, stemless plants of fire-prone eucalyptus woodland to large, trunked species of rainforest margins and montane grasslands. The name means “large Zamia,” though several species are anything but large. For gardeners in Mediterranean and warm-temperate climates, Macrozamia offers some of the most garden-worthy and surprisingly cold-tolerant cycads available outside the African Encephalartos.
Taxonomy
Family Zamiaceae, order Cycadales. Approximately 41 accepted species (World List of Cycads). The most comprehensive treatment is that of Jones (2002) and Hill (various publications). The genus is divided into two informal groups: section Macrozamia (spirally arranged leaflets, larger species) and section Parazamia (leaflets in a single plane, often more compact).
Geographic range and diversity
Endemic to Australia: eastern Queensland, New South Wales, south-eastern South Australia, south-western Western Australia, and isolated populations in the Northern Territory. The greatest diversity is in Queensland and New South Wales. Habitats range from dry sclerophyll forest and heathland (Macrozamia communis, Macrozamia spiralis) to subtropical rainforest margins (Macrozamia moorei) and montane grasslands above 1,000 m (Macrozamia johnsonii).
Fire ecology
Many Macrozamia species are profoundly adapted to fire. Their thick, subterranean or semi-subterranean caudices survive bushfires that destroy above-ground vegetation, and cone production is often dramatically stimulated by fire. In fire-suppressed landscapes, Macrozamia populations can decline as competing vegetation closes the canopy.
Conservation and CITES
Several species are threatened by habitat clearing and urban expansion, particularly in the rapidly developing coastal regions of Queensland and New South Wales. Macrozamia pauli-guilielmi is Critically Endangered. All Macrozamia species are listed under CITES Appendix II. Australian state legislation provides additional protection, and collection from the wild is illegal without permits.
Cultivation
Light
Full sun to partial shade. Open-habitat species (Macrozamia communis, Macrozamia spiralis) tolerate full sun and even prefer it. Rainforest-margin species (Macrozamia moorei) appreciate filtered light in the hottest climates but handle full sun in milder areas.
Temperature and cold hardiness
- Hardy (−6 to −10 °C, USDA zone 8b–9a): Macrozamia communis (the hardiest and most widely cultivated species — tolerates brief frosts to −8/−10 °C in well-drained soil), Macrozamia spiralis, Macrozamia moorei (from montane grasslands — cold-tolerant once established).
- Semi-hardy (−2 to −5 °C, USDA zone 9b): most subtropical Queensland species.
- Tender: tropical species from far-north Queensland.
Substrate
Well-drained, sandy or gravelly soil with moderate organic content. Many species grow naturally in sandy, acidic soils — reflecting their Australian sclerophyll habitat. A mix of coarse sand, composted bark and pumice works well. Slightly acidic to neutral pH.
Watering
Moderate during the growing season. Reduce in winter. More drought-tolerant than most Zamia but less than Encephalartos from arid habitats.
Propagation
Dioecious. Hand pollination as for other cycad genera. Seeds are large, bright red or orange-red when mature (sarcotesta). Remove sarcotesta, soak, and sow half-buried at 25–30 °C. Germination typically occurs in 6–16 weeks. Seed dispersal in the wild is by emus, cassowaries and large rodents. Seedling growth is slow. Some species (Macrozamia communis) sucker and can be divided.
Pests and diseases
Root rot in waterlogged soil. Scale insects occasional. The cycad blue butterfly (Chilades pandava) is a growing threat in Australia. Aulacaspis yasumatsui has not yet reached most Australian Macrozamia populations but is a serious biosecurity concern.
Species of Macrozamia
Approximately 41 species, all endemic to Australia.
Section Macrozamia (spirally arranged leaflets)
- Macrozamia moorei — Queensland; the largest species; trunks to 7 m; montane grasslands
- Macrozamia johnsonii — Queensland highlands
- Macrozamia montana — New South Wales
- Macrozamia mountperriensis — Queensland
- Macrozamia diplomera — New South Wales
- Macrozamia parcifolia — Queensland
- Macrozamia platyrhachis — Queensland
Section Parazamia (leaflets in one plane)
- Macrozamia communis — New South Wales; one of the hardiest species (−8/−10 °C); the most widely cultivated
- Macrozamia concinna — New South Wales
- Macrozamia elegans — New South Wales
- Macrozamia spiralis — New South Wales; similar to Macrozamia communis; cold-hardy
- Macrozamia lucida — south-eastern Queensland; subject of Terry et al. (2007) thermogenesis study
- Macrozamia miquelii — Queensland; widespread
- Macrozamia riedlei — Western Australia; zamia palm; widespread
- Macrozamia fraseri — Western Australia
- Macrozamia dyeri — Western Australia
- Macrozamia fearnsidei — Queensland
- Macrozamia flexuosa — New South Wales
- Macrozamia heteromera — New South Wales
- Macrozamia pauli-guilielmi — Queensland; Critically Endangered
- Macrozamia reducta — New South Wales
- Macrozamia secunda — New South Wales
- Macrozamia stenomera — New South Wales
Authority websites
The Cycad Pages — Royal Botanic Gardens Sydney
https://plantnet.rbgsyd.nsw.gov.au/…
Palm and Cycad Societies of Australia (PACSOA)
https://www.pacsoa.org.au/wiki/Macrozamia
World List of Cycads — https://www.cycadlist.org/
IUCN Red List — https://www.iucnredlist.org/
Bibliography
Jones, D.L. — Cycads of the World. 2nd edition, 2002. The standard reference for Australian cycads.
Hill, K.D. — “The genus Macrozamia” (various publications in Telopea). Comprehensive taxonomic revisions.
Whitelock, L.M. — The Cycads. Timber Press, 2002.