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The following have been selected from the questions received on the ASGAP World Wide web site over the past few months. You're welcome to comment on any issue concerning Australian native plants....growing, propagating or appreciating (even loathing!) ... anything.

If necessary, bung a message in a bottle if your net connection goes down!!


Grevilleas in high phosphorus areas

I planted grevilleas in my garden and the leaves are slowly turning yellow. I was told it is the area where I live because the soils are high in phosphorus. Is the something I can put in the soil or spray the plants to overcome this problem.


Grevilleas and related plants such as banksias can be adversely affected by excessive phosphorus but there could be a couple of reasons for your problem. One is phosphorus toxicity and another could be nitrogen deficiency.

Firstly - how certain are you that your soils are high in phosphorus? Although there are exceptions, Australian soils tend to be low in phosphorus unless they have been previously heavily fertilised. If phosphorus toxicity is the problem in your case, it's more likely to have been a result of applying a fertiliser to the plants rather than a problem with the soil itself. The safest fertilisers to apply to grevilleas (to most native plants, in fact) are slow release types specially formulated to have a low phosphorus concentration. These will often be found in nurseries with a name like "native plant food". Normal general fertilisers can cause problems because they release nutrients too quickly and can be high in phosphorus.

The bad news is that, if phosphorus toxicity is the problem, there's not a lot you can do. If the plants are small you could try to recover them by transplanting them into pots, using a potting mix designed for native plants. If they recover you could plant them out elsewhere. Other than that, all you can do is water frequently and don't fertilise. They may recover.

If nitrogen deficiency is the problem, you can water the foliage with iron chelates. This is available in nurseries and is usually effective. This is probably worth doing as it won't do any harm even if nitrogen deficiency isn't the cause of the yellowing.

Good luck with them.


Where do I start?

I have recently started upon the stressful task of building a new home. So within the next 6 months I will have a beautiful home, so the only thing left is to create the beautiful garden to go with it.

I am looking to create a wonderful Australian Native garden that my children can hopefully play in, but also one that their parents can retreat to or entertain in. Which brings me to the question, "Where do I start?"

I was hoping someone could point me in the right direction to a point of resource that may answer some of the questions that beginners have. I am a novice gardener, but have a keen interest in creating the perfect Australian Native garden for my new 1/4 acre home in the suburbs. Can anybody help..?


There's a series of articles on "Getting Started" in back issues of "Australian Plants online" You'll find them between June 1998 and March 2000.

The ASGAP website also contains a wealth of information (admittedly, not all directed at beginners). Spending a bit of time browsing the site would probably answer a lot of your questions. The Frequently Asked Questions section could be useful.

You can also get a lot of good ideas by visiting places where Australian plants are grown. Some of these are large parks and gardens but they can still produce great ideas for planting smaller areas. There are quite a few in Victoria - see the list on our website.

Finally, another good resource is a District Group of the Society. I'm not sure if there is a District group located near you but you could find out more from the Victorian Region's website.


Australian plants in the USA

I'm a retail store manager and I have a customer who relocated from Australia and are looking for plants native to Australia, that grow in our climate. Unfortunately our climate is zoned to winter cold down to -23 to -29 degrees Celsius. The plants they mentioned are:

  • Grevillea
  • Banksia
  • Boronia
  • Myrteaceae
  • Anigozanthos
  • Eucalyptus

I have been able to find Callistemon and Grevillea for them but they will be annuals in our zone. Can you recommend any extremely cold hardy varieties of the aforementioned plants, or any other cold hardy plants and ways I might be able to locate them? Any information you could provide would be greatly appreciated. Thank you for your time.

Michigan, USA,

-23 degrees Celsius! Holy mackerel!!

   Banksia canei
   Eucalyptus pauciflora
   Banksia canei (top); Eucalyptus pauciflora (bottom)
Click for a larger image

This is going to be extremely difficult. There are unlikely to be any Grevillea, Anigozanthos or Boronia that will tolerate those extreme conditions. They just don't grow naturally in that sort of climate. It's possible that some may adapt but there is no major city in Australia where those conditions occur so we just don't have any experience to draw on.

There are a few eucalypts and banksia that may adapt. The only ones that come immediately to mind are Banksia canei and Eucalyptus pauciflora. You could obtain seed of these fairly easily - see Seed suppliers on our web site.

The only Australian nursery that I know of that specialises in cold climate species is Dealbata Australian Plant Nursery, off Bloomfield St, Dalgety, NSW, 2630. They don't seem to have an email address but the phone is 02 6456 5043.

There are a few nurseries in the USA that sell Australian species. I don't know if they will be able to help but it would be worth contacting them.


Potting up a Hakea

We are going to move to a smaller house but want to take a Hakea with us - this is one of my husband's favourites.

It is about 300 mm high at the moment and as we aren't moving until next year thought we had better get it into a pot now.

What would be the best potting mix to use and should we use a native long lasting fertiliser which is what I use in the garden?


Any potting mix designed for "Australian Natives" should be fine. These are low in phosphorus, which should suit the hakea as well as a wide range of native plants. The actual brand names will vary from place to place.

These specialised mixes usually contain slow release fertiliser so I wouldn't add any additional fertiliser at this stage. A small amount of slow release fertiliser in late spring would probably be enough until you plant it out.


Pruning melaleucas

   Melaleuca quinquenervia
   Melaleuca quinquenervia
Click for a larger image

I live in San Diego, California. We have melaleucas on our street and though they are beautiful they are blocking our beautiful views. They are Melaleuca quinquenervia and are about 14 years old. They have been successfully trimmed in the past but for the last two years the gardeners have only thined them believing that topping them 4 feet would be bad for them.

May I have your opinion?

California, USA

M.quinquenervia is pretty tough - I wouldn't expect it to be weaked by removal of 4-5 feet. Pruning may encourage branching and a bushy crown but it will probably send up vertical growth in time. I'm not sure that the appearance of the tree would be improved by pruning, however.

Of course, the behavior of the plants in your climate may be different to their behavior here, but most of the larger melaleucas respond well to pruning.


What Kennedia is that?

   Kennedia rubicunda

Click for a larger image

I wonder if you can help me with question as to whether there has been a name change in the Kennedia genus.

Kennedia rubicunda grows on Angels Beach East Ballina. We wanted to purchase some extra plants recently and nursery offered "Kennedia nigrum". This plant is not listed in the Flora of New South Wales, so wondered whether a name change had occurred?

Ballina, New South Wales

I'm not aware of changes in Kennedia. It's most likely that your nursery person was referring to K.nigricans, a species from Western Australia....definitely not native to northern NSW!


What does 'subcrenulata" mean?

I have a question that I hope you can answer for me. I have read the article Understanding the System of Botanical Plant Names by Bruce Wallace (Australian Plants online Issue 27 ). I was wondering what "subcrenulata" means (as in Eucalyptus subcrenulata)?


According to "The Encyclopaedia of Australian Plants" by Elliot and Jones, 'subcrenulata' means 'somewhat crenulate'. Which, I suppose is somewhat cryptic if you don't know what "crenulate" means......

I guess the derivation is as follows:
* crenulata = "with small rounded teeth"
* sub = "under, below, approaching"

So the foliage of this species would have teeth along the margins but the teeth would be small in comparison with species having truely crenate leaves.

I hope that helps.


Boronia perfume

   Boronia megastigma    Boronia megastigma 'Harlequin'
   Two forms of Boronia megastigma:
The normal brown form (top) and
the cultivar 'Harlequin' (bottom)
Click for a larger image

Generally I have an excellent sense of smell, but I cannot smell Brown Boronia. I even enjoy the smell of white azaleas.

Would you know where I can find some more info on this?


Commiserations on not being able to appreciate Boronia. My sense of smell is not all that good but I can smell Boronia.

It's certainly known that the ability to appreciate different scents varies between people but I'm not aware of any research on this topic. I can only suggest that you try the Australian National Botanic Gardens. If any information is available, they should be able to point you in the right direction.


A sick cushion plant

I have a Cushion plant, Scleranthus biflorus, that is over 10 years old and until recently covered an area of around 1m square. Large parts of the plant have started to yellow, then turn burn and completely die. I can only think that it is being attacked by some kind of fungus.

Is anyone familiar with this dieback and have any solutions?


I don't grow this plant but I think this sort of problem is not all that uncommon. Wrigley and Fagg "Australian Native Plants" report that die back can be caused by the Rhizoctonia (a fungus). Apparently, this can be controlled by an appropriate fungicide.

I asked "Gumnuts" readers for their experiences and the following response from Alex McLachlan might help.

"I have that same problem in Canberra and it can look quite messy, especially when the blackbirds get into it and spread the dead stuff over the foliage still alive. Mine usually dies in late summer (after I get back from holidays) so I thought it might have been a lack of water but I have had some dieback this winter.

One good outcome is that if you don't remove the dead areas it should break down and the seeds (of which there should be thousands on a plant of that size) from last summer will germinate in the plant's own mulch. This happened to me in the last few years and you can then gently thin out some of the seedlings and pot them out. I had dozens and was giving them away to whoever wanted them.

Another bonus is the seedling in situ with the best genetics (or if they are all clones????? the strongest ones) for that particular area will survive out of all the seedlings and should last longer. I don't think I've got any of the 'original' plant left but a number of smaller plants. I haven't tried a fungicide.


Toxic Hardenbergia?

Could you please tell me if it is save to plant Hardenbergia on a fence were stock could eat it?

   Hardenbergia violacea

Click for a larger image

Will stock eat it?

Is Hardenbergia violacea poisonous to cattle, sheep, horses etc??


I can't find any information on the potential toxicity of Hardenbergia to stock. However, it is known that early European settlers used the leaves as a tea substitute so it is probably safe.

To be certain you would probably need to contact a scientific organisation such as the Australian National Botanic Gardens which has access to a substantial research library or the local office of the Agriculture Department in your state.


Toxic Cooktown Ironwood?

I have a question about Cooktown Iron Wood. I have got some of kitchenware made of them.

I confirmed that it is Erythrophleum chlorostachys, but I found that this tree is toxic for mammals especially for live stock.

I just wonder if it affects us as users of those kitchen wares such as plates and chopping board?


I can't provide advice on this. Presumably the reported toxic effects resulted from livestock eating the foliage of the plant but I have no information on the toxicity of the wood.

Perhaps other readers may have advice to offer.


Rust on gum leaves

I have a 3 metre tall Corymbia "Summer Red" grafted gum that is my pride and joy. It's growing in full sun, clay soil, is staked, and flowered profusely last summer. Now it has begun to get a red rusty rash-like appearance on its leaves. I think I should cut off the lower branches, as they touch the ground, but should I then spray the tree with a fungicide?

New south Wales

It's almost impossible to diagnose these sorts of things from a distance. The foliage discolouration could result from a range of causes, including fungal (rust) diseases, soil nutrients or lack of water. It could even just be a response to cold weather. You really need to take a sample to a reputable nursery in your area or, better still, a local NSW Agriculture office if there is one near you.

If it is a rust, then spraying with a fungicide may help. You can see some photos of a eucalyptus rust in this document - this may help you decide if it is a rust problem.

If it's not a fungus then probably there's not a lot you can do at this stage other than making sure it doesn't dry out. If it doesn't recover with new growth once the weather warms up, you should definitely get some local expert advice.


Grafted 'Silver Princess'

   Eucalyptus caesia

Click for a larger image

I recently found at a Sydney nursery a grafted Eucalyptus caesia 'Silver Princess' for sale. They couldn't tell me what species was used for the understock. Does anyone know anything about this plant? Given the difficulty with fungal diseases in Sydney with E.caesia, will this grafted plant be any more successful on the east coast?

Sydney, New South Wales

Unfortunately, growers tend to be a bit secretive about these things and it's very difficult to find out what root stocks are used.

Eucalyptus caesia is in the sub-genus Symphyomyrtus which includes lots of other species so there are lots of possibilities for the rootstock.

My guess is that the grafted plant will be more successful but grafting of this species is fairly new and I doubt there are many (none?) mature trees that we can use as a guide.


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Australian Plants online - September 2004
Association of Societies for Growing Australian Plants