The Tropical Fruit Forum

Take a look at my website page with photos of wild Citrus australis plants growing in D'Aguilar National Park, about 50miles from Brisbane.
http://www.homecitrusgrowers.co.uk/australiannativecitrus/citrusaustralis2.html
You will see the various different leaf forms as the plant matures. The juvenile leaves are just like yours.

Australian desert soils are not always alkaline - in fact many are acidic. Most information suggests that Citrus glauca prefers slightly acidic conditions.
Are your examples of Citrus glauca seedlings or grafted? If grafted, it is the rootstock that determines the pH requirement and not the top variety.

I used to incorporate coconut husk chips into my citrus growing medium. They work well and provide reasonable drainage but only for a couple of years. After that they break down and encourage root rot. I no longer use them.
The same applies to standard bark mulch. The bark chips sold as 'orchid bark' or 'reptile bark' are much harder and will last much longer.
You should investigate the availability of Danish Moler Clay in Belgium. It is a form of fired clay granules which can absorb moisture while providing excellent drainage, and is often used by bonsai enthhusiasts. It does not break down. Here in England it is expensive if bought directly for horticultural use but can be found much cheaper when sold for use as cat litter or oil-spill absorbant. I now use it as the major ingredient in my potted citrus mixes.

For several years I have been using a mix containing 50% 'danish Molar Clay'. This is sold in UK as some cat litters and also as a spill-absorber. The producer in Denmark is https://www.imerys.com/minerals/moler

In the UK and many countries outside USA it is not possible to patent plants because they are not considered to be inventions. Instead 'plant breeder rights' can be registered for new cultivars. The first person to be given plant breeder rights over a microcitrus variety was Erika Birmingham of Byron Bay Nurseries in Australia. She became quite paranoid about the possibility that native Australian citrus would be exploited overseas, as happened with Macademia nuts. The inevitable has now happened and her concerns have been proved correct.
It is interesting to note that the name SunLime is very similar to the Australian registered Sunrise Lime. This variety and the Red Centre Lime (previously Blood Lime) have had very limited commercial success in Australia. I suspect this is because they are basically an acidic fruit which can be used as an ingredient or garnish but are not very desirable to eat as they are.
I have been growing microcitrus for many years and have produced several interesting hybrids. Saga University in Japan also experimented with such hybrids some years ago. Details of some of these are available on my website at http://www.homecitrusgrowers.co.uk/australiannativecitrus/sagauniversityhybrids.html

I have seen something similar which disappeared completely after a couple of years. I put it down to the effect of some chemical.
As I asked on the other forum you posted on, have you fertilised recently? If so, with what and how much? Any chance of drift from nearby weedkiller or path clear chemical?

It looks to me like coconut husk chips.  Are you using that as growing medium or just a top mulch?
I used CHCs for several years for my potted citrus but found they break down fairly quickly into an unhealthy and often soggy mix. For a couple of years they are fine, although getting the watering right is difficult. But after that things go downhill and root rot often sets in.

Calamondin - Citrus mitis.

We know that Buddha's Hand is always propagated vegetatively because it does not produce seeds, but I've never heard of any hybrids before. I've always assumed that the pollen is not viable and that the fingered fruit would have died out without human intervention. If the pollen is viable then it may or may not carry the 'defective' gene which produces fingered fruit. Clearly, with this hybrid the trait has not been passed on. The resulting plant may be no different from a Kumquat hybrid with some other citron variety.

I was given budwood of US119 in 2001, grafted it onto Poncirus rootstock, and planted it outside here in UK in 2004.
It has survived down to -15C, most winters the minimum is around -6c, but it has grown so slowly and never yet flowered.
I believe the real problem with growing citrus here is the short summer growing period.
We only have 3 months guaranteed frost-free and most varieties just don't have enough time to put on summer growth before they become dormant again.
My 119 is about 1.5m (4 - 5 ft) tall. Perhaps this year it will produce fruit - but I've been saying that for the past 15 years!

If as you say this is a grafted tree then it seems the graft is very near ground level or below ground.
This means that it has been planted much too deep. The graft line should always be well clear of the ground so rain reaching the ground does not splash dirt on to the trunk and cause infection. That is one of the reasons for having a rootstock which is less susceptible to phytophthora than the top variety.
I think that the darker and slightly sunken area just below the main forking branches may be a sign of phytophthora infection.
If it is phytophthora and it has completely circled the trunk, there is little hope for the tree.
A really valuable tree could possibly be saved by grafting new rootstocks above the infection - a process called inarching.
This was carried out on the Parent Washington Navel tree in Riverside. See my photos at
http://www.homecitrusgrowers.co.uk/riverside/parentwashingtonnavel.html

Citrus glauca (previously called Eremocitrus glauca) does hybridise easily with other species.
Over 25 years ago I managed to germinate only one seed from several sent to me from Riverside.
It soon became clear this was a hybrid which I jokingly called 'Eremowhat?'.
This plant is still a vigourous potted tree about 8 feet tall and fruits each year.
You can read a rather old web-page about it at http://www.homecitrusgrowers.co.uk/australiannativecitrus/eremowhat.html