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Short Cuts

Short items of interest about Australian plants selected from the many newsletters and journals published by member Societies of ASGAP.......

Short Cuts in this issue:

BulletGolden Guinea Tree
This tropical species deserves to be better known in cultivation
BulletGrowing Golden Penda
A spectacular rainforest tree for tropical and sub-tropical gardens
BulletGrowing Grevillea from Seed
Grevilleas can sometimes be difficult to germinate - these tips should help
BulletPropagation for the Casual Grower
An easy propagation method for those just wanting a few extra plants for the garden
BulletFifteen Ideas for Garden Design
A few rules to help create an appealing landscape
BulletGrafting Grevillea caleyi
Grafting may hold the key for protecting an endangered species

Golden Guinea Tree

Dillenia gives its name to the family containing the much better known Hibbertia (Dilleniaceae). With only a single species found in Australia, Greg Calvert thinks Dillenia alata deserves to be better known

  Dillenia  alata
  Dillenia  alata
  Dillenia alata
Top: Flowers. Bottom: Fruit
Photos: Garry Sankowski

Throughout the far north, along creeks, swamps and littoral rainforest, grows a most attractive tree. The golden guinea tree (Dillenia alata) has a lush, attractive appearance that softens the harshest of landscapes.

Like the beautifully flowering hibbertias, D.alata has an exquisite yellow flower with a red centre. The flowers last for only a day before the petals fall and litter the ground beneath the tree. This does make one somewhat less remorseful about plucking the petals off to eat, as did Aborigines throughout their range.

The yellow flowers give rise to a spectacular, bright red, star-shaped fruit. Within each arm of the star is contained several small black seeds, each enveloped with a soft white aril. This aril is edible with a taste reminiscent of coconut. Birds also enjoy these fruits and people who sleep in late rarely ever beat the birds to the delicacy.

Identification of the golden guinea tree is particularly simple when the tree is flowering or fruiting. However, there are other features that make this tree distinctive at any time of the year. The leaves have a large 'wing' growing out the side of the petiole (leaf stem) and are the only species of tree I have ever seen with such an arrangement.

Of all the features of Dillenia, it is the bark for which it is best known. The bark is a bright, coppery red and peels off in thin sheets, finer than tissue paper. Artists who specialise in making 'bark pictures' by cutting and pasting different bark types to create a scene often seek this bark for its bright vivid colours.

Golden guinea tree is readily propagated from seed and makes an attractive addition to a tropical garden. Although the red flaky bark takes some years to develop, the plants flower and fruit in as little as two years.

It should be noted that this species loves wet feet; so if there is a corner of your garden that is poorly drained and difficult to grow plants in, then this is your tree!

From "The Native Gardener", Newsletter of SGAP Townsville Branch, June 2000.

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Growing Golden Penda

Another spectacular tree from tropical Queensland, Xanthostemon chrysanthus is related to the much better known bottlebrushes and eucalypts. Norm McCarthy has the story....

Xanthostemon is a genus of about 45 species of tropical or sub-tropical trees. Ten species are endemic to coastal north Queensland, the Northern Territory and northern Western Australia while an odd one may occur as far south as the Qld/NSW border in rainforest habitats, often near creeks and streams.

Xanthostemon chrysanthus, or "Golden Penda", is probably the best-known and most widely grown species of all. it is found naturally in north-east coastal Queensland.

It can easily be propagated from fresh seed, though slow to germinate. The seed ripens from January to April as a general rule presenting as a hard nut approximately 1 cm diameter.

However, this plant is usually grown from cuttings of a mature specimen using semi hard material for speed of reproduction and earlier flowering. Seed could take much longer (even years) to produce flowers, whereas cuttings taken from superior forms are more suitable, reliable, quicker to bloom and true to type.

Golden Penda was a highlight at "Expo 88" in Brisbane, being produced enmass and planted in flower as small shrubs. It presents as a 'Sea of Gold' and has been popular ever since for gardens in south-east Queensland and beyond. These special plants were produced in large numbers from cuttings of a superior form in a Brisbane garden and revelled in the popular name of 'Expo Gold'.

Xanthostemon chrysanthus Xanthostemon chrysanthus  
Golden Penda - Xanthostemon chrysanthus
Photos: Richard Logan
Click thumbnail for larger image

This attractive tree may reach 12 metres x 10 metres in cultivation in large rainforest gardens with ample sunlight. Judicious pruning may contain this beautiful tree to a large shrub, if desired. In it's natural wild state it could be a tree of 15 metres of more in competition.

Leaves are pleasantly dark - shiny green with reddish brown new growth; the shape is elliptical with a marked central vein and may measure 18 cm x 5 cm. Foliage is stiff and crowded. Although it has dense foliage when young, some pruning may be required to maintain shape and compactness to increase flowering potential.

Flowers present in mostly terminal heads in striking multiple florescences of pure spidery gold flowers. A single floret could measure up to 5 cm in diameter with numerous long golden stamens radiating from a green central rachis, subtended by five golden sepals. Individual stamens terminate with prominent pollen presenters or anthers. The flowers are enormously attractive to nectiverous birds.

Being of the Myrtaceae family the blooms are reminiscent of the large flowers of a eucalypt, at first glance.

I would consider Golden Penda could be suitable for growing as a hardy rainforest specimen in sub-tropical, coastal situations with adequate protection under well watered conditions. Copious mulching and regular feeding of slow release additives is an obvious advantage.

This large shrub or tree develops a trunk, which is hard, durable and becomes rough, scaly and brown to grey in colour. This makes a pleasant adjunct to the attractive foliage.

The tree is a breathtaking sight in full bloom, which commences from late winter in north Queensland through to autumn according to its climatic situation, it is indeed a joy to behold.

Cooler climates may restrict height, speed of growth, flowering size and quantity of bloom to a later time cycle.

An excellent large indoor pot plant, Golden Penda needs light, warmth and moisture and is reasonably frost hardy in the garden.

What more can I say to impress you?

From "Native Plants for New South Wales", newsletter of the Australian Plants Society (NSW), October 2001.

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Growing Grevillea from Seed

Grevillea seeds have a reputation for unreliable germination but Neil Marriott has a few 'tricks of the trade' to improve your success rate.

For many years it has been known that Grevillea seeds are highly unreliable and erratic in their germination. Sometimes seed germinates well, but often it is very poor or comes up over several (often many) months.

I have been growing grevilleas by seed for many years now, and have finally developed a process that gives almost 100% success. I do not use any fungicides as they are too dangerous. However, you can use them if you wish, but by sticking to the following steps you should not need to.

  • Make sterile seed mix: 3 parts Perlite to 1 part sieved peat moss. Moisten with clean tap water and firm and level into trays till they are just over half to two thirds full.

  • Sow smoked* and soaked seed thinly over seed mix. Then cover seed with at least 1cm of the same mix. Water in well. I have discovered that Grevillea seed germinates far better when sown deeply in the mix.

  • Place the seed trays outside in a sunny site and well off the ground, e.g. on an old table.

  • Check moisture level of mix and water, normally this means daily watering. Never allow to dry out or all your seed will be lost.

  • I find mid to late spring to be the best time to sow seed in Victoria. This allows seedlings to be potted up and well established by next autumn. However, autumn sowing gives equally good results but many seedlings can be lost through first winter if they are not well developed by the time the cold weather arrives.

Most species of Grevillea have an inbuilt dormancy factor which prevents them from germinating when night minimum temperatures rise above 15oC.

* Smoked water is available commercially under the Regen 2000 label.

From the newsletter of ASGAP's Grevillea Study Group, July 2001.

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Propagation for the Casual Grower

Looking for a simple, low maintenance method to propagate a few extra plants for the garden...no mess....no fuss?? Ross Doig shows you how!

The title could have included the words "in miniature" as this method employs a capillary bed which confines seed raising to a self-contained, portable system. Widely used by Society members as an effective aid for raising a wide range of native plant seeds using pots, tubes and punnets, its advantages are:

  • Fine seed is watered from below without disturbance
  • Moisture content is controlled
  • A number of seed raising containers may be used simultaneously
  • a minimum of maintenance as watering is governed by the size of the inverted bottle, for example a 2 litre PET bottle might only require refilling fortnightly.

However, most of my propagation is from cuttings and not wishing to involve myself in systems requiring misting and bottom heat, the capillary system suggested itself as an adjunct to my present system. To this end I trialled small 50 x 70 mm tubes and 2 litre PET bottles (with the bottoms cut out) for about 60 sets of cuttings with good results, subject to certain limitations mentioned below.

Capillary bed diagram   
Cross section of a capillary bed containing both cuttings and seedlings   

The capillary bed took the form of a foam box (courtesy of my local fruit and veg merchant) cut down around the sides to 110 mm (measured from the outside) to facilitate easy removal and replacement of the PET bottles. Polythene sheet was used as a liner and a bed of sand or sand and coco-peat to a depth of 30 mm put on top of it.

Into this bed, the filled inverted water bottle was placed with the threaded section of the neck below the surface of the sand. It was held in position by an inverted "u" bridge made of stiff wire mesh, a section large enough in the centre being cut out into which the bottle neck was screwed. Other methods of holding the bottle in position could be devised. To start up the bed merely wet the sand and place the filled bottle in position.

A propagating mix of fine gravel/sand or fine gravel/coco-peat (with proportions of the latter varied to allow for susceptibility of certain plants to rot in the very humid situation) was put into the tubes and the cuttings, with or without hormone treatment, tamped in lightly. Three pots went under each PET bottle. Watering was done at this stage but subsequent watering of tubes was very occasional as the tubes were are buried up to 10 mm in the sand bed.

Conclusions to date

  1. The method is worth persisting with as cuttings may be left for at least two weeks without attention and both seeds and cuttings can be kept in the one container while at the same time be portable.

  2. The humid atmosphere created by the PET bottles causes cuttings to make roots faster than is the case with other cold systems. In winter fungal and mildew problems may be experienced with soft new growth, hairy plants and some herbaceous types so that with susceptible material part of the neck of the PET bottle should be cut away. After October and through to autumn this has been found to be unnecessary.

  3. Inspection of the cuttings in individual tubes can be made without disturbing other cuttings, although it is possible to place a single 100 mm pot of assorted species cuttings under one PET bottle.

  4. A large number of cuttings, 33 sets to be precise, under 11 PET bottles (and the water bottle) can be accommodated in an average size foam box.

  5. The controlled moist/humid environment, and warmth retention capability, allows small cuttings of 30 mm length to be used alongside larger than usual cuttings, up to about 170 mm and for more leaves to be retained (more sugar produced, faster more vigorous roots formed).

  6. The box should be kept in a well lit environment with morning sun desirable but not essential. A verandah, pergola, the southern wall of the house, under the shade of shrubs or trees, a shadehouse or glasshouse are all suitable. When in the open overhead shelter from rain is a must.

As I said in the beginning, if you fit the casual grower category, give it a go!

From "Calgaroo", newsletter of the Parramatta and Hills Group of the Australian Plants Society.

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Fifteen Ideas for Garden Design

A garden should be more than just a collection of plants. Diana Snape has a number of suggestions for you to think at the planning stage.

I was asked by Helen Moody for some suggestions for designing with Australian plants, to be included in an article she was writing for the Sydney Morning Herald (4/9/97). In her article Helen says "The most distinctive quality of Australian plants and native gardens is that they impart a spirit of place that is uniquely ours. They create a feel, a sense, a smell and a sound of their own."

Here are those idea as I wrote them....

  1. A garden is an artistic creation which evolves through time and is never 'finished'; gardeners are artists who follow their own vision and those of us who love Australian plants can gain inspiration directly from aspects of the Australian landscape.

  2. Plants which occur naturally in the same environment - desert, for example, or coastal - usually look happy together in the garden because of their complementary adaptations as well as their similar requirements.

  3. Sculptural Australian plants, like tree ferns, grasstrees, Gymea lilies and banksias, will distinguish a garden and deserve to be treated with respect and placed carefully in a garden landscape.

  4. Three or four different species of the numerous Australian groundcover plants - daisies, hibbertias (Guinea flowers), scaevolas (fan flowers), etc.- can be chosen and repeated to create a lovely tapestry effect at ground level.

  5. Even in a small garden, a tree of the appropriate size such as one of the smaller eucalypts extends the space of the garden upwards, acting as a focal point as well as being a magnet for birds.

  6. Don't just look at the shapes of the plants in a garden, look also at the shapes of the spaces between plants; the balance of 'mass' and 'void' should be satisfying.

  7. Australian daisies and grasses combine nicely with rocks - a pleasing contrast of soft and hard textures, with clumped or sprawling daisies and tufted grasses complementing the definite curved or straight lines of rocks.

  8. A huge variety of fine foliaged tufted Australian plants look excellent beside water - rushes, sedges and lilies, either upright or weeping. There are shrubs and small trees too with weeping foliage which is very appealing when reflected in water.

  9. A sympathetic formal touch - a well made stone wall, paving of appropriate colour and outline, or sculpture - can bring solidity to the fine foliage of many Australian plants.

  10. Australian rainforest plants continue to gain popularity because of their colourful new foliage, flowers and fruit; with glossy green leaves of medium size they blend well with exotic plants.

  11. There are many small-leaved Australian plants (eg. lilly pillies, melaleucas, leptospermums, westringias) which can be pruned and treated formally for hedges or even topiary, to be used for example as a focal point among less formal shrubs.

  12. From the variety of Australian shrubs now available, such as the range of beautiful grevilleas, it is possible to create wonderful massed or layered garden beds with colour schemes which can be vivid or subtle. Remember to tip prune.

  13. The rapid growth of some large shrubs or small trees, in particular some acacias, is of benefit in planting for succession - it enables them lo be used as 'nurse' plants lot a screen and tor shelter while slower growing plants are being established.

  14. A garden of low shrubs (a metre or less, pruned if necessary to maintain this height) gives an open and spacious feel to the garden while several small eucalypts with fine trunks could provide a vertical element.

  15. The variety of foliage of Australian plants is amazing, in form texture, colour - from large and dramatic to tiny, delicate leaves - and many attractive effects can be achieved with foliage alone.

From the newsletter of ASGAP's Garden Design Study Group, November 1997

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Grafting Grevillea caleyi

Many people think Western Australian plants are the only plants which are better off grafted in eastern Australian gardens - as Mark Ross shows, eastern species can benefit from the practice as well.

Grevillea caleyi is a rare shrub local to the Sydney area which, on its own roots, tends to be short lived and can die suddenly unless on very good drainage.

  Grevillea caleyi
  Grevillea caleyi
Photo: Peter Olde (from The Grevillea Book Vol.2)

Grafting it onto Grevillea robusta (silky oak) allows it to be grown on a wide range of soils and live for a lot longer. It grows more vigorously - there is a grafted specimen at Mt Annan Botanic Gardens, which must be 6 metres across and 3 or so metres high.

G.caleyi is an attractive shrub with great horticultural potential. Its main feature is its ferny foliage with purplish new growth and sprawling lateral habit.

It is actually an easy plant to graft. I have used the top wedge and approach method and have found that either is normally 99% successful.

Grafting times on average are between mid spring to late summer but G.caleyi can be done between late winter to late autumn. When the rootstock is actively growing, the graft strikes in approximately 10 to 14 days and active growth start about 2 weeks later. I have found that even though the scion is quite hairy, misting improves success rate.

This plant may be a little leggy at first when grafted on to G.robusta, but if pruned heavily while young, it will become rather dense and very wide up to 4 metres. It can withstand min temp to minus 5oC (4 days in a row, June - July 2002) with very little damage (slight tip damage on a 2 yr old plant). The plant can also handle extreme temperatures and hot dry winds.

From Native Plants for New South Wales, newsletter of the Australian Plants Society (NSW), October 2002.

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Australian Plants online - June 2003
Association of Societies for Growing Australian Plants