Thought I'd just share some of my recent experience with growing JBPs in Townsville.
When I first moved up here 2 years ago, I was adamantly told by the president of the local bonsai club that pines did poorly in Townsville


Being a stubborn fool, I figured given Hawaii successfully grows JBPs (see Lindsay Farr's Papa Kaneshiro video), perhaps the above advice could be grouped with the general myth of pine bonsai and taken with a degree of doubt.
So what's happened thus far:
Repotted two of my more mature JBPs in late July. I gave them a reasonable root prune and within 4 weeks they have solidly anchored themselves in their pots. They haven't missed a beat. Perhaps the use of Auxinome helped with root growth. I'm using Auxinome for the first time and find it seems to have some effect - more than Seasol anyway which some experts state is all hype and marketing anyway. (Interestingly, I've checked and found there's little scientific evidence backing the claims Seasol and associated seaweed products make - and that's coming from someone who grows organic vegies etc) Needle growth reflects the root growth and the shoots are all over. Notably like other posters have indicated in their experience, my candle lengths aren't very long at all. Maybe 5 cm or so. I thought this may reflect poor growing conditions, but the shoots are all over the place so maybe shorter candles are a feature of the tropics? Perhaps it's because the trees were only recently repotted. I did get long candles >10 cm on other training trees though that were not repotted.
The mix I've tried up here is Maidenwell 2-7 mm diatomite mixed with some local Quican rock (really just small basalt gravel - a bit like Coco Pops) and some organic Debco potting mix. The Quican rock acts a bit like rock dust and seems to give my trees a deep green colour. BTW I use the Debco organic mix because it's basically just composted pine bark without the water saving crystals you get in conventional mixes. I just find the crystals swell up during prolonged rain and disrupts the pot. Ideally if I had more time i'd use sieved composted pine bark but the Debco mix seems to do the job straight from the bag. Besides because I'm only using the pine bark to increase my potting mix's CEC ratio and are relying on the diatomite and Quican rock for the air porosity and drainage properties, I figured i could cut a small corner and save some hassle of sieving. Fertiliser comes in the forms of osmocote, chicken manure-based pellets and worm juice. I find the mix rewets really easily and allows me to give the trees a wet-dry cycle pines and other conifers appreciate. According to the Japanese, this cycling also encourages coniferous trees to fill their pots with roots. It's just hard to do with pine bark based mixes.
I have not noted any mycorrhizial growth. This is despite the use of predominantly organic fertilsers and allowing a wet-dry cycle with my watering. I suspect it's because of my growing conditions. Mycorrhizae on pines in nature are most important in enviroments where the soil is cold and infertile. It helps pines absorb the last bit of nutrient from their surrounding soil. (Also note temperate climate gardeners also find organic fertilsers don't work as well for them because the microbial activity needed to convert organic fertilsers to usable nutrients plants can absorb is much lower in cold soil. Thus I suspect mycorrhizae partnerships are more important in pines grown in much colder climates found in Europe and North America) How relevant is this to trees in a warm climate which are heavily fertilised? I suspect this is why the mycorrhizae I had previously has now disappeared.
As a side note, 4 of my trees have flowered and I've got 6 small pine cones underway on sacrifice branches. Amazingly, one of my one year old seedlings I'd sowed myself had some male flowers appear. The trees with cones are upwards of 5 years old. Apparently according to conifer texts I've found, JBPs are well known or becoming sexually mature at a young age i.e. several years. This compares quite differently to most other Pinus species which are upwards of 20 years.
I've hand pollinated the cones with male pollen from another tree. Note that JBPs can have male and female flowers (i.e. cones) on the same plant simultaneously like other pines. However, while pines can self pollinate, the successful fertilisation rate drops down to roughly 50%. This is a phenomenon seen in other pine species too. I presume it's a mechanism which encourages genetic diversification but allows propagation if the tree is by itself and is unable to be fertilised by another tree. The cones take about 2 years to mature, so i will see what happens. I do note others (e.g. Shibui) have stated their seeds from their first cone crops on their younger trees yielded no viable seeds. So it will be interesting to see. I guess the other thing to consider is that are my trees trying the replicate because they're happy or because they're stressed? After all, plants flower and fruit better when stressed.
I sowed JBP seeds last year and had a 70% germination rate by the tissue towelling method Brent Walston described. I tried again this year and got a 91% germination rate after sowing direct to a loose potting mixing. There was no need for stratification which is so commonly advised in all the forums. That advice has been wrongly anounced by some and unfortunately is repeated onwards. JBPs are not high mountain pines and do not rely on a chilling period to remove the natural seed retardents found in other Pinus species.
Anyway, lots of info there. I hope it helps. Now all I need to work out is a needle size reduction method that works in the tropics. need to do more research
