The feature plants in March, Macrozamias and Pittosporum, are a slight departure from my usual garden plant posts, but I wanted to include a few native species and we are growing both a Macrozamia and a Pittosporum in our garden. We also consider Mimosa Rock National Park to be an extension of our garden! Plus, this is the time when both plant species are prominent in the forest with their eye-catching bright red seeds.
It’s March and it’s Harvest Time in the bush! The native animals in the forest are having a field day sourcing all their favourite berries. Mimosa Rocks National Park has some beautiful forests of Spotted Gum (Corymbia maculata), whose understorey is full of Macrozamias and Pittosporum. They are both very different in structure, reproduction, lineage, growth rates and toxicity. I shall be focusing on Macrozamia communis, Pittosporum undulatum and Pittosporum revolutum.
- Commonly known as Burrawangs, the name given to them by the Dharuk Aborigines of the Illawarra and Sydney regions. The Dhurga aborigines of the South Coast called it : ‘Bung-go ib-bur’, meaning ‘nut’.
- Its scientific name is derived from 2 Greek words : ‘macros’ meaning ‘large’ and zamia, referring to its genus, while its species name comes from the Latin word ‘communis’ meaning ‘common’, as these plants are abundant in dense stands.
- Endemic to the East coast of NSW, it is the most common cycad, with the most extensive distribution of any cycad in NSW , ranging from Taree on the Central Coast to the Bega area, 600 km to the south.
- They grow in coastal areas, as well as the coastal slopes of the Great Dividing Range (and occasionally the inland slopes) as far west as Mudgee.
- It is the most southerly occurring cycad in the world and is most abundant on the South Coast of NSW, where it has the greatest overall size, cone size and population density. Near Bateman’s Bay, the stands are so extensive and dense that the ground is often obscured, though many have been cleared for urban development.
- No other cycad in NSW, or indeed Australia, has such a great population density as Macrozamia communis.
- Macrozamia communis is an understorey plant in wet and dry schlerophyll forests.
- On the South Coast of NSW, it is the dominant understorey plant in Spotted Gum (Corymbia maculata) forests, while on the Central Coast, it grows under forests of Sydney Red Gum (Angophora costata), also known as Smooth-barked Apple. It also grows under Bangalay Gums (Eucalyptus botryoides) at Aragunnu.
- In coastal areas, it grows on sandy soils, with its population density being greatest on stabilized sand dunes, close to the ocean, while on the coastal ranges, it grows on gravelly loams.
History : Macrozamias are fascinating plants.They are cycads, a small group of plants with unique features and a very ancient lineage.
- First appearing in the fossil record in the Late Permian, 250 Million years ago before the Age of Dinosaurs, they quickly spread to every continent and latitude from Siberia to the Antarctic throughout the Mesozoic Era.
- The Jurassic period of the Mesozoic Era is in fact known as ‘the Age of Cycads’, when cycads and gingkos were the dominant plants and there are 19 extinct genera of cycads from that time.
- Now, there are only 3 families left with 11 genera and 250 species, compared to the 300,000 species of Angiosperms (or Flowering Plants).
- Once classified as Gymnosperm along with conifers and gingkos, cycads are now considered to be a sister group to all other living seed groups.
- They are found in tropical and subtropical regions of the world and each genus has a restricted geographical range, often being limited to specialized or localized sites like areas with nutritionally deficient soil, limestone or serpentine outcrops, beach dune deposits and very steep slopes.
- Macrozamias are endemic to Australia and have 25-32 species, depending on your source! They belong to the Family : Zamiaceae, which has 8 genera including : Dioon, Encephalartus, Macrozamia, Lepidozamia, Ceraiozamia, Microcycas, Zamia and Chigua.
Unique Features of Cycads:
- Pachycaul stem– its soft thick trunk is mainly storage tissue with very little true wood;
- Collaroid roots with symbiotic relationship with cyanobacteria, not seen in other seed plants;
- Large divided fern-like/ palm-like leaves with no axillary buds, like other seed plants;
- Reproduce by seeds produced on open carophylls (seed-bearing leaves or scales), arranged in cones;
- Cycads are dioecious– the male and female reproductive structures are on separate male and female plants;
- Cycads have also been exploited as a food source for a long time, but require extensive processing to remove toxins, the methods differing between areas and over time.
Description: Macrozamia communis : Medium to large cycad with a height and spread of 3m. They are very slow growing and long-lived – up to 120 years. They take 10-20 years to mature and produce cones.
Roots : Like all cycads, the roots are contractile: the sensitive growing apex of seedling is drawn below the soil surface, providing protection against drought and fires. The roots are also collaroid : the upper root rises above the ground and contains cyanobacteria, which fix atmospheric nitrogen for the cycads, in return for a stable source of fixed carbon in the form of carbohydrates produced by photosynthesis and protection from harsh environmental conditions and grazing. While cyanobacteria are capable of producing their own fixed carbon, cycad roots reach deeper into the soil and can spread over far larger areas. Nitrogen is essential for the production of genetic material and the structural and enzymatic molecules in all stages of the life cycle and is especially important in the nutritionally deficient soils of many cycads.
Stem : Only producing a single trunk with no suckers, the trunk is 30-80 cm diameter and 30-200cm tall and is typically underground, though plants on shallow soils or rocky quartzite or sandstone ridges often have a short columnar trunk.
Leaves : 50-100 glossy dark green, pinnately compound leaves up to 2m long, which form a gracefully arching crown extending from a central trunk. Each leaf has 70-130 pointed leaflets (pinnae) in 2 rows and they decrease in size to sharp spines at the end of the leaf.
Reproduction: Cycads are dioecious and do not produce flowers. Male and female reproductive organs are borne on separate plants, the seeds on scales arranged in large cones (strobili) like conifers. The cones are often formed after fire. The male plant bears 1-5 cylindrical erect cones, which droop after their pollen is shed. The female plant bears 1-3 wider barrel-shaped cones, which are pollinated by Macrozamia Weevils (Tranus internatus) and mature in March, when they break apart to release 100-150 bright red-orange seeds throughout Winter. The seeds have no dormancy, so are very short-lived and subject to damage by dessication (drying-out). They are dispersed by Brush-tailed Possums (Trichosurus vulpecula), who break the cones apart to eat the fleshy outer coat of the seeds without damaging the stony inner layer, so the embryo remains viable and germinates readily after dispersal. The major predator of the seeds is the Native Bush Rat (Rattus fuscipes), who gnaws through the stony layer to eat the seed contents, including the embryo.
- Food source : The seeds have a high starch content and containing macrozamin, which is toxic to humans and livestock. It requires extensive processing to remove the toxins. The Cadigal aborigines pounded and soaked the seeds in water for a week, changing the water daily, while others soaked the seed in running stream water for several days. The pulp was then made into cakes and roasted over hot embers.
- Tools were made from the strongly barbed leaf shafts.
Horticulture : Highly ornamental, cycads have been in cultivation for many years. There are planted in many different ways :
- Feature Plant
: Single specimen
: Paired either side of entrances : doors, gates, driveways, like in Asia.
: In a rockery or in a tropical or desert setting, where a large crown is desired without the tall trunk of a palm.
- Mass Plantings : ground cover
- Containers : small gardens; patios and verandahs; bonsai specimens
Easy to cultivate and hardy, M. communis is suited to temperate and subtropical regions and can survive temperatures as low as -8 degrees Celsius. Hardiness Zone : 8b-11
They tolerate a wide range of soils, but do best in deep sandy soils, and prefer partial shade, but will adapt to full sun, so long as they get adequate water. These tough plants are drought-tolerant and suitable for xeriscaping. They are also fire-retardant.
Good drainage is ESSENTIAL.
They grow best with a uniform and regular supply of water during the growing season and a good nutrient supply : fertilizer with an even NPK balance. eg: a regular dressing of slow release Osmocote.
They transplant readily, but as their growth is so slow, it is probably unnecessary. If transplanting, do it in late Spring and be careful of the sharp spines.
Potted Cycads require bright light and plenty of fresh air and normal room temperature (10-27 degrees Celsius). Use soil-based potting mix with broken pottery shards in the base of the pot for good drainage and stand pots on trays of moist pebbles to get the correct humidity. Keep the soil moist, but not wet, with extra watering when the temperature is above 27 degrees Celsius and mist spray foliage occasionally. A fortnightly dressing of complete fertilizer can be applied throughout the growing season.
: Seeds : Germinates easily without pre-treatment. Plant seed in well-drained potting soil in a shaded location and water regularly till germination in 6-24 months. Early seedling growth is very slow.
: Offsets : cut off parent plant with sharp knife, leaving as minimal a wound as possible. Treat wound with fungicide (eg sulphur), dry for 1 week, then plant into sterile medium.
Pests and Diseases
: Mealy bugs : apply an insecticide twice during growing season
: Scale insects : occasionally infest the crown. Same treatment as above or use white oil
: Macrozamia weevil : causes sporadic deaths in wild populations
: The fleshy starch-rich stems are susceptible to fungal attack and stem rot.
Pittosporum undulatumName: Known by a number of names including : Sweet or Orange Pittosporum; Native Daphne; Australian Mock Orange; and Cheesewood, its scientific name is derived from the Greek words : ‘pitta’ meaning ‘pitch‘ and ‘sporos’ meaning ‘seed’, referring to the resinous sticky coating of the seeds; and the Latin word : ‘unda’, meaning ‘wave/ surge‘, referring to the wavy edge of the leaves.
- Family : Pittosporaceae : includes Native Frangipani (Hymenosporum flavum); Bluebell Creeper (Billardiera heterophylla) and the genus Bursaria.
- Genus : Pittosporum : A very large genus in Australia and warmer areas like Africa, Asia, Pacific Islands and New Zealand. There are 14 species in all states of Australia.
Distribution and Habitat:
- Moist gullies in rainforests and wet schlerophyll forests, as well as sheltered situations in dry schlerophyll forests and woodlands.
- Coast and subcoastal districts of Eastern Australia from SE and Central Qld to Eastern NSW, ACT and Eastern Victoria.
- Naturalized in Tasmania and King Island; SE South Australia; SW Western Australia; Lord Howe and Norfolk Islands; as well as Southern Europe (France, Spain, Portugal); South Africa; St Helena; the Azores; India; China; Hawaii; Mexico; SW USA (California); Carribean and South America (Bolivia, Colombia and Chile).
- Significant environmental weed and is on the Global Invasive Species Database.
Description : Large evergreen tree, usually 4-14m high with a 7m spread, creating dense shade underneath.
Bark : Coarse grey, while younger shoots are green to reddish-brown.
Leaves: Smooth, glossy green (darker on top, paler underneath), elliptical or ovate leaves with pointed tips and entire distinctively wavy edges. They are arranged alternately on their stems or clustered at the tips of branches.
Flowers : Small, creamy-white, highly fragrant, bell-shaped (tubular) flowers, borne in small terminal clusters of 4-5 flowers in Spring and Early Summer (November-January). Each flower has 5 petals, which are fused together at the base of the corolla and reflex backwards at the tips. They are pollinated by Lepidoptera (moths and butterflies).
Berries : Hard globular or slightly flattened capsules, 1cm diameter, formed in Autumn and lasting several months. They produce their first seed at 5 years old. The capsules turn from green to yellow to orange, then tan when mature, when they split open to release 20-30 sticky, smooth, red-brown, angular seeds, which are very attractive to possums, frugivorous birds and even foxes, often sticking to fur, clothing and footwear. The seeds have short to medium longevity. They germinate in abundance after fire or soil disturbance.
- This plant contains Saponins 152 and 154, which cause dopiness and are fairly toxic to humans, but are poorly absorbed by the body, so tend to pass through without any problems. However, stock should be kept away from infested areas. Saponins are also very toxic to fish and the aborigines used to put large amounts in streams and lakes to stupefy and kill the fish.
- The opened seeds can be boiled up to produce a gum to smother Pitosporum seedlings in fragile areas.
- The wood has been used in the manufacture of golf clubs.
Horticulture : Well established as a garden ornamental plant in Australia and California and also clipped into hedges and used as windbreaks. They are hardy, adaptable and quick growing. They like most acidic soils and extra moisture and prefers granite-derived soils. They can withstand extended dry periods once established and resist maritime exposure.
It is very invasive in bushland and easily colonizes moist gullies and disturbed soil in areas of urban development. It is most invasive in areas of high rainfall. It has very rapid growth and adapts to soil with higher nutrient levels more readily than other native species. With changes in fire regimes, it out-competes fire-adapted native species. It dominates other species through dense shading, competition and its superior adaptability to changes in soil nutrients. The berries are also very attractive to birds, so it can be dispersed widely and its spread is very difficult to control. Therefore, do NOT grow near bushland! This website has information about its management especially after fire : http://www.herbiguide.com.au/Descriptions/hg_Pittosporum.htm.Having said all that, we did plant a specimen (see above photo) in our town garden, as the scent of the flowers is superb and despite its feral status, I am still very fond of Sweet Pittosporum! But if you live near bushland, I have included some short notes on an alternative Pittosporum species, which is also very attractive at the moment and is a much safer bet!
Pittosporum revolutumName : Commonly known as Rough-Fruited or Yellow Pittosporum, its species name : ‘revolutum’ means ‘rolled backwards‘, as some leaves are at the edges.
Distribution and Habitat : Endemic to Australia, this species mainly grows in coastal areas, west to the Blue Mountains and Muswellbrook and from sea level to 1100m. It
grows in rainforest and wet schlerophyll forests in Queensland, New South Wales and Victoria and in dry schlerophyll forests in the south.
Description : Understorey shrub 1-3 metres high.
Leaves : Glossy dark green, ovate or oblong to elliptic leaves with entire but rarely undulate margins and arranged alternately on the stem or clustered at the end of the branch. The young leaves and the lower surface of mature leaves have a dense to sparse covering of rusty hairs, especially around the main veins, giving a slightly furry feel to the undersides of the leaf.
Flowers : Bears fragrant yellow flowers in terminal clusters in Spring. The petals reflex backwards and the sepals, inflorescence and ovary are all covered in rusty hairs.
• Slightly compound, amber or orange, ellipsoid or oval capsules with hard thick walls,which often have hairy and warty valves. They ripen in Autumn and break open to reveal numerous red-brown to bright scarlet, very sticky seeds, which are popular with birds.
Use : Was eaten by the aborigines, but has a slightly bitter taste.
Horticulture : Its use as an ornamental plant is now gaining in popularity. Outstanding plant, even in a small garden. It prefers shady areas under large trees.
I hope you enjoy this lovely watercolour painting, painted by my daughter specifically for my Bush Harvest post. They are very cute Native Bush Rats!