Burrawang
Macrozamia communis
The Burrawang (Macrozamia communis) is a species of cycad in the family Zamiaceae, endemic to the east coast of Australia. It is one of the most widespread and commonly encountered cycads in New South Wales.
Cycads are among the most ancient lineages of seed plants, often referred to as "living fossils" because their basic body plan has remained largely unchanged for hundreds of millions of years. The Burrawang exemplifies this deep evolutionary heritage.
• Cycads predate the dinosaurs, with fossil records extending back to the Permian period (~280 million years ago)
• Unlike flowering plants, cycads are gymnosperms — they produce seeds but not enclosed fruits
• Macrozamia communis is the most southerly-distributed species of the genus Macrozamia
• The common name "Burrawang" is derived from the Dharuk (Darug) Aboriginal language of the Sydney Basin region
Taxonomie
• Range extends from the south coast of New South Wales northward into the central coast and Sydney Basin
• Found from near sea level to approximately 1,000 meters elevation
• Grows in open eucalypt forests, woodlands, and coastal heathlands
• Prefers well-drained sandy or rocky soils, often on ridges and slopes
The genus Macrozamia is entirely Australian, comprising approximately 40 species, with the highest diversity in eastern Australia. Cycads as a group were once globally distributed across all continents during the Mesozoic era, but today survive as relict populations in tropical and subtropical regions worldwide.
Trunk & Caudex:
• Trunk is typically subterranean or partially emergent, forming a stout woody caudex
• Above-ground portion, when present, can reach up to 1–2 meters tall in mature specimens
• Trunk diameter typically 20–50 cm
• Covered with persistent leaf bases that give a rough, textured appearance
Leaves (Fronds):
• Crown of stiff, dark green, pinnate fronds radiating outward
• Each frond is 1–2 meters long with 80–200 pairs of leaflets
• Leaflets are linear-lanceolate, 10–25 cm long, with entire margins and a slightly recurved shape
• Leaflets are arranged in a flat plane along the rachis, giving the crown a distinctive flat-topped silhouette
• New fronds emerge in flushes (called "leaf flushes"), covered in brown tomentum (fine hairs) that wears off as leaves mature
Reproductive Structures:
• Dioecious — individual plants are either male or female
• Male cones: cylindrical, 15–30 cm long, 5–8 cm diameter, borne singly or in small clusters
• Female cones: ovoid to cylindrical, 20–40 cm long, 10–20 cm diameter, among the largest cones of any cycad
• Seeds are ovoid, 3–4 cm long, with a fleshy outer sarcotesta that turns bright orange-red when ripe
• Seeds are among the largest of any Australian plant species
Habitat:
• Open eucalypt forest and woodland, particularly on nutrient-poor sandy soils
• Coastal headlands, ridges, and well-drained slopes
• Often found beneath a canopy of Angophora, Corymbia, and Eucalyptus species
• Frequently associated with heathland margins
Fire Ecology:
• Highly fire-tolerant; the subterranean caudex and thick leaf bases protect the growing point from low-intensity bushfires
• Fire stimulates new leaf flushes and can trigger cone production
• Plays an important role in post-fire ecosystem recovery by providing structural habitat
Pollination:
• Relies on insect pollination, particularly by host-specific weevils (family Curculionidae) and thrips
• Male cones produce volatile chemical compounds and heat (thermogenesis) to attract and disperse insect pollinators
• This insect-mediated pollination system is considered an ancient evolutionary strategy predating the rise of flowering plants
Seed Dispersal:
• Brightly colored fleshy sarcotesta attracts native mammals and large birds (e.g., emus, brush-turkeys)
• Seeds are heavy and generally fall close to the parent plant, resulting in limited dispersal range
• Some seeds are cached by rodents, which may aid in secondary dispersal
• Populations are generally stable in protected areas and national parks
• Localized threats include habitat clearing for urban development, particularly in the Sydney Basin
• Illegal collection of wild specimens for horticulture is a concern in some areas
• Climate change and altered fire regimes may pose long-term threats to population viability
• All Australian cycads are protected under state and federal legislation; collection from the wild without permits is illegal
Toxic Compounds:
• Cycasin — a glycoside (methylazoxymethanol glycoside) that is both neurotoxic and carcinogenic
• Macrozamin — an azoxyglycoside unique to Macrozamia species
• β-Methylamino-L-alanine (BMAA) — a non-protein amino acid neurotoxin linked to neurodegenerative diseases
Toxicity in Humans:
• Ingestion of raw seeds or foliage causes severe nausea, vomiting, abdominal pain, and diarrhea
• Can lead to liver failure, coma, and death in severe cases
• BMAA has been implicated in the neurodegenerative disease known as "lytico-bodig" (similar to ALS/parkinsonism-dementia complex) among the Chamorro people of Guam, who historically consumed cycad-derived food
• The seeds were processed into a starchy food by Aboriginal Australians using elaborate leaching and washing techniques to remove toxins before consumption
Toxicity in Animals:
• Livestock (cattle, sheep) that ingest leaves or seeds may develop "zamia staggers" — an irreversible hind-limb paralysis caused by damage to the spinal cord
• Dogs and cats are also susceptible; ingestion can be fatal
• The bright orange-red sarcotesta of ripe seeds is attractive to animals and humans alike, increasing the risk of accidental poisoning
Light:
• Prefers full sun to partial shade
• Tolerates a wide range of light conditions but produces the best growth in bright, open positions
Soil:
• Requires well-drained soil; intolerant of waterlogged conditions
• Adaptable to sandy, loamy, or rocky soils
• Tolerates nutrient-poor and slightly acidic to neutral soils (pH 5.5–7.0)
Watering:
• Extremely drought-tolerant once established
• Water regularly during the first growing season to establish roots
• Reduce watering significantly once mature; overwatering can cause root rot
Temperature:
• Hardy to approximately -4°C once established
• Tolerates light frost but may suffer leaf damage in severe cold
• Thrives in warm temperate to subtropical climates
Propagation:
• Primarily by seed, which is slow to germinate (can take 12–18 months)
• Seeds should be sown fresh, with the sarcotesta removed
• Can also be propagated by removing and rooting basal offsets ("pups")
• Very slow-growing; may take 10–20 years to reach reproductive maturity
Common Problems:
• Scale insects and mealybugs may infest the crown
• Overwatering leading to caudex rot
• Leaf burn from excessive fertilizer application
Anecdote
Cycads like the Burrawang have one of the most remarkable pollination strategies in the plant kingdom — a partnership with insects that evolved long before flowers existed. Thermogenic Cones: • Male cones of Macrozamia communis undergo thermogenesis — they actively generate heat • Cone temperatures can rise 5–15°C above ambient temperature during pollen release • This heat volatilizes chemical compounds that attract pollinating weevils and thrips • The cycle follows a daily rhythm: cones heat up in the late afternoon, releasing odors that draw insects in, then cool at night, trapping the insects inside the cone • The following morning, the cycle reverses — the cone heats again, the insects become active and pick up pollen, and are then released to visit another plant Ancient Symbiosis: • The insect-cycad pollination relationship is estimated to be over 200 million years old • This makes it one of the oldest known specialized pollination mutualisms on Earth • The weevils that pollinate Macrozamia are often host-specific, meaning the survival of the pollinator is directly tied to the survival of the cycad Aboriginal Food Processing: • Aboriginal Australians developed sophisticated methods to detoxify Burrawang seeds, including prolonged leaching in running water and fermentation • The resulting cycad flour was a significant food source in some regions • This represents one of the earliest known examples of complex food processing technology in human history
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