Common Name:

General Information

Macrozamia riedlei is a slow-growing, evergreen, palm-like plant usually with a subterranean stem but sometimes becoming emergent to a height of up to 25cm and and 24 - 40cm in diameter; this is topped by a crown of around 10 - 30, erect to spreading large leaves each around 120 - 220cm long[]
Although poisonous unless properly treated, this species has been an important source of food for the native people where it grows. The plant is also of potential importance as a source of starch for food and other purposes, and is grown as an ornamental.
Although Macrozamia riedlei has declined in parts of its range due to habitat loss, it is an extremely abundant and resilient species that is not regarded as threatened. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2010)[].

Known Hazards

None known

Botanical References

Range

Australia - Southwestern Western Australia

Habitat

An understorey plant in jarrah forests and woodlands and also occurs in low heathy scrub[].

Properties

Conservation Status	Least Concern
Edibility Rating
Other Uses Rating
Habit	Evergreen Shrub
Height	1.50 m
Growth Rate	Slow
Pollinators	Insects
Self-fertile	No
Cultivation Status	Ornamental, Wild

Cultivation Details

Macrozamia riedlei is native to a mediterranean type of climate with its hot, dry summers and cool to cold, moist winters where moderate frosts can occur. Mean annual rainfall is in the range 250 - 1,000mm annually, falling mostly in winter[1935
An almost universal requirement for cycads is a well-drained but moisture-retentive soil, and by far the best soils are sandy gravels and light loams which provide the required drainage and aeration necessary for good growth. Cycads will generally not grow well in clay soils unless those soils are heavily amended with sand and organic matter[]. A neutral soil (pH 7), is generally best for most species of cycads and allows the proper absorption of nutrients. A slightly acid soil is better for most cycads than a basic one[].
Cycad species can usually be transplanted easily even when quite large. The best time for moving them is just before the beginning of a new growing season, the roots being trimmed if they are damaged and perhaps some leaves being removed. New roots should develop quickly as the season progresses[].
Species in this genus form structures known as coralloid roots. These roots branch off from the taproot or secondary roots and are distinctive in that they grow laterally or upward, forming a nodular mass at the apex. These coralloid roots occur slightly below or slightly above the soil surface and generally contain cyanobacteria, also known as blue-green algae. These are able to fix atmospheric nitrogen and make it available as a nutrient to the plant. The ability to extract this important nutrient from the air explains how many cycad species are able to survive on almost sterile soils[].
A dioecious species, with individual plants producing either all male or all female cones. Therefore both male and female forms of the plant need to be grown if seed is required[]. On very rare occasions, usually when a plant has been under severe stress, it can change sex and produce either all female or all male cones[].

Edible Uses

Caution should be employed if using any part of this plant for food. All parts of the plant can contain toxins and can only be eaten if proper measures are taken to remove these toxins.

Seed - cooked[]. A chief source of food for some Aboriginal groups[]. Non native people have very differing opinions on this food, with some finding it disgusting, rancid, and like train oil), while others consider it quite as good as that of a chestnut[]. The irregularly ovoid, often somewhat flattened seed is 45 - 50mm long and 25 - 35mm in diameter[].
In the natural state the pulp surrounding the seed is poisonous. In order to remove the toxic principles, the seed is soaked n water for a few days, then it is buried in sand and left there until the pulp is nearly dry. It is then fit to eat, usually after roasting[[].
Seeds were processed by natives of south-western Australia by deeply burying and leaving to leach for 6 - 12 months. In this case, the fleshy sarcotesta was eaten rather than the starchy endosperm[].

The fleshy layer of the seeds contains around 28% of a bright orange oil whose physical and chemical constants were found to resemble those of palm oil[]

The plant is of potential commercial importance as a source of starch from its stems. The pith of the stem is dried either in the sun or by heating in an oven, it is then shredded up and soaked in water for six hours. It is then shaken
up and filtered, the milky fluid being allowed to settle. The sediment is washed several times, dried slowly, and finely powdered, and is ready for use[]..

Medicinal

None known

Other Uses

A gum is exuded from the cones, stems and bases of the leaves, often as a result of insect or other damage.
Gums of the various species of Macrozamia are nearly identical in character. It occurs in flattened pieces resembling 'button lac', in scaly pieces that have been likened to unbleached and unpurified gelatin, and in tears. Placed in water, the gum begins to swell almost immediately. The absorption of water goes on for several days, by the end of which the gum has swollen to from 50 - 100 times its original size. It then has the appearance of a colourless, quivering jelly. This behavior is much like that of cherry or acacia gums to which Macrozamia gums are apparently quite similar[].
The gum of Macrozamia was suspected once of being responsible for the poisonous effects of these plants but has been exonerated[]

Propagation

Seeds - best sown as soon as they are ripe, though the seeds of many species will take a few months to finish maturing the embryo before they are ready to germinate. Sow the seeds in a tray in a freely-draining medium and place in moderate shade. Bottom heat at about 27°c will hasten seed germination dramatically. Young roots are quite brittle and once germination takes place, the root grows rapidly. It is important to pot up the seedlings at this time in order to give them enough root-space. Grow on the plants in pots until large enough to plant out[].