AusBonsai

Hello everyone,

I bought a Shimpaku juniper last week, but I am unsure what type of Shimpaku it is. I need some help identifying the tree. Additionally, I plan to repot it soon, but I'm unsure what soil mix would be best for it. I want to let it grow more before transferring it to a bonsai pot. Any advice would be greatly appreciated. Thank you.

Some of the differences between cultivars are very slight. Probably not possible to tell the difference from online photos.
FWIW it looks like regular shimpaku to me.

shibui wrote: ↑April 22nd, 2024, 6:24 pm Some of the differences between cultivars are very slight. Probably not possible to tell the difference from online photos.
FWIW it looks like regular shimpaku to me.

Thank you, Shibui. I think so too, but the foliage is very green compared to my other Shimpaku (which I believe is Sargentii), and it looks really compact. I was just wondering if you could help me out with something. I'm curious about the soil mix for my Shimpaku trees. Do you think a mix of 80% perlite and 20% coco coir would work well? Thank you so much for your help!

Need to be a bit wary of juniper variety names. There was much confusion around juniper species in the past, let alone cultivars. We saw the same plants sold under a range of different names - x media, Sargentii, and many more. I note that Yamina rare plants is covering all bases with one of their cultivars which is listed as "Juniperus chinensis (x media) sargentii Shimpaku.
Differences in colour can sometimes be attributed to cultivar but foliage colour also varies with conditions so this tree's colour may be related to previous sun/shade/water/fertiliser, etc. I'd give it a while to adjust and see whether the difference persists.

Potting mix for bonsai is more about what suits your conditions and care habits than the species. Most of the trees we grow are remarkably adaptable and will grow well in a wide range of soil types so growers in different areas use a wide range of potting mixes successfully. I use one standard mix for all the trees I grow here. That saves having lots of different components and mixing individual brews for each species or remembering what goes in which mix. I grow a wide range of species and all seem to do well in that one standard mix.

Perlite is a great product. It is inert, long lasting, holds water and comes in a range of particle sizes and is low density/ light weight. It's big drawback is that it is very light. Particles tend to 'float' out of the mix when you water and blow away in windy conditions. Light weight components are great when lifting larger pots but growers who have used perlite also find that trees are far more likely to tip over an/or fall off the benches in windy conditions.

Coir is also a useful growing component. It has neutral pH, holds water and breaks down relatively slowly. The usual concern for bonsai pots is that it can hold water a bit too well which may lead to root problems in some conditions, depending on your watering habits and local rainfall.

I have not used the combination you specified so can't comment on the 80/20 mix and even if I had tried it your conditions are unlikely to be exactly the same as anyone else and your care program will also be different so the best you're likely to get is that it works/doesn't work for someone else.

My feeling, and from what I've read from those who have tried these components, is that there are better mixes for bonsai in general.

Juniperus Chinensis ''var sargentii'' (shimpaku cv ''Kishu'')

I am using perlite and coir for a development mix. They are both very cost effective for larger quantities, which was my deciding factor. Between 60-80% perlite.
I have a wet summer/autumn, where it rains more days than it doesn't. So I am trying to have large particles to add aeration to the roots to thrive. My observation is that a high portion of perlite is good to allow the soil to have good airation.
I think better products out there but it suits me for now.
I would also consider pumice, pine bark, scoria. Really depends on what you can get in your area within your budget.
I have found I end up having to topdress the mix with to avoid it blowing away in the first few months after repotting. The mix appears to stay on drier side, but dig down .5cm and it holds moisture.
I have a few junipers in a range of mixes and the perlite one are doing very well. Actually better than my previous mix of pinebark + sand/gravel, scoria.
Agree difficult to identify different shimpaku foliage types.

Thank you all for your helpful responses. I will try that combination with some of my trees and see how it turns out. I agree that coco coir holds a lot of water. I may be overwatering my plants so that I will try a different substrate in the future.

dattran27 wrote: ↑April 22nd, 2024, 8:28 pm I'm curious about the soil mix for my Shimpaku trees. Do you think a mix of 80% perlite and 20% coco coir would work well? T

I agree with Shibui that this mix is probably not the ideal one. Coco is often high in sodium which needs to be leached out. It also needs iron and copper added to it. It is also low in sulphur. After soaking and leaching, adding Iron sulphate at about 1 gram/litre and Copper sulphate at about 0.2 grams/litre will fix that. You may then need slowly add a dolomite/lime mix to bring the pH to about 6.5 if the iron sulphate has decreased it too much. All this has already been done for you with potting mixes which conform to the Australian Standard and you will most likely get better results with those after adding at least 50% sharp quartz sand. That will also provide ballast and stop the pots blowing over all the time. Perlite is ok but very light and a bit of a pain at 80% of the mix - floating to the top with a lot of coir at the bottom of the pot or washed out.

Agree wholeheartedly with Mike on potting mixes.
Sounds easy - just add a few components and grow great plants.

Reality is there's a lot of science behind successful potting mix - Air filled porosity, Water holding capacity, pH, micronutrients, etc. Once you understand how the different components interact and what they supply it is OK to roll your own but for smallish quantities that will actually grow plants well it is far easier, and often cheaper in the long run, to purchase a good quality commercial potting mix.

Thank you, Mike and Shibui,

After reading all of your analyses, I have decided to change my soil mix immediately. I searched online for the quartz sand that Mike mentioned, but there are many types and I'm not sure which one is the right one. Do you have any recommended brands for potting mix and quartz sand?

Sand is generally inert so the type of sand is less important but the particle size is more critical. I look for 3-10mm particle size or 3-6mm if possible. Sometimes sold under different names like propagating sand.
Avoid beach sands (generally very fine grains and salty) and fine particle brickies sand or sandpit sand which will have lots of smaller particles in the mix.

shibui wrote: ↑April 25th, 2024, 5:09 pm Agree wholeheartedly with Mike on potting mixes.
Sounds easy - just add a few components and grow great plants.

Reality is there's a lot of science behind successful potting mix - Air filled porosity, Water holding capacity, pH, micronutrients, etc. Once you understand how the different components interact and what they supply it is OK to roll your own but for smallish quantities that will actually grow plants well it is far easier, and often cheaper in the long run, to purchase a good quality commercial potting mix.

With the potting mixes, even ones that conform to the AS (5 white ticks on a red or black background) there are (were) good ones and not so good ones. The main problem is that some are to fine for our purposes so you will need to invest in ay least one sieve or preferably as many different ones as you can find. Then can you may sift out the dust of the (dry) mix. Alternatively, you can add a courser mix like an orchid mix to open it up and then add the sand. For the sand, it's probably easier to visit you local garden supply joints and buy a bag or three from them. They usually stock something you can use. You can also add scoria to your mix along with the sand. Junipers do not seem to mind it.

I apologize for my delayed response.

I came across a soil mix online and was wondering if it would be suitable to mix it with 10% bark and 80% quartz sand (so most of the mix will be sand and 20% organic). I plan to use a fabric pot, as some online sources recommend, to prevent overwatering.

The bark and sand should be fairly inert so should be OK as a mix.
80% sand is a very well drained mix so you will need to water a lot to keep the trees happy. Should be almost no risk of root rot though dehydration is a possibility.
There's no nutrient in the mix and very little CEC to hold nutrients so you will also need to fertilise often. Make sure you are using a fert with trace elements. Iron deficiency can be a real risk with these very open potting mixes so best learn the signs and be ready to add chelated iron if needed.

"Thank you, Shibui. I will try it out first and learn more about chelated iron."