This is probably not helpful to a beginner asking a simple question for which there is a very simple answer. Everyone who’s been doing this for a while knows this can be as complicated as you want it to be.All decent substrate for bonsai has water retentive properties and junipers very much like water, just not like that of bald cypress. If you included only non-water retaining substrates in your mix, you'd be watering like a mad man. But junipers adaptable, to a degree.
The size of the substrate is arguably just as much an issue as the substate itself. The larger the particle size equals less water-retention capacity and more aeration capacity.
Based off this study:
Their findings:
Organic Substrates
Inorganic Substrates
- Coconut Coir: 129g @ 14.57% loss
- Compost: 26g @ 31.58% loss
- Pine Bark: 22g @ 33.33% loss
- Commercial Peat Moss: 6g @ 40% loss
24-hour Retention Rankings
- Diatomaceous Earth: 37g @ 30.19% loss
- Akadama: 22g @ 26.67% loss
- Kanuma Pumice: 22g @ 29.03% loss
- LECA (Turface): 30g @ 36.17% loss
- Vermiculite: 28g @ 41.67% loss
- Perlite: 14g @ 36.36% loss
- Sand: 12g @ 67.56% loss
- Lava Rock (Scoria): 4g @ 76.47% loss
- Expanded Shale: 2g @ 84.62% loss
- Granite Chips: 1g @ 94.44% loss
Organic Substrates:
Inorganic Substrates:
- Coconut Coir
- Compost
- Pine Bark
- Commercial Peat Moss
Akadama, lava rock, and pumice (2:1:1 ratio) is commonly suggested as the 'gold standard' for juniper and other bonsai.
- Diatomaceous Earth
- Akadama
- Kanuma Pumice
- LECA (Turface)
- Vermiculite
- Perlite
- Sand
- Lava Rock (Scoria)
- Expanded Shale
- Granite Chips
For the sake of this study, Akadama is one of the most water retentive of the substrates next to Napa 8822 (diatomaceous earth) -- and so is pumice. With a 2:1:1 of akadama, lava rock, and pumice, with water retention at ~ 61% water retention with ~17g weight.
Another, popular, cheap method is sifting Napa 8822 or Floor Dry, mixed with half perlite and 10 percent pine bark. 1:1:0.10 ratio, equaling ~ 67% water retention with ~ 25g weight.
The amount of water retained by both are acceptable. So long as it is a fast-draining substrate that retains water for the roots to stay moist and to allow air in for roots to breathe, it's really the same. The only thing that would change is frequency in watering and esthetics.
Though, the confounding variable in this study is the particle sizes not being measured, only its weight was. Common substrate mixes are not mixed together at different ratios and then measured. Also, the measurements are taken in only one environment and for only one day out of the year -- not to mention it didn't show any bonsai being grown successfully in the substrates.
But if the particle size is increased, the water retention and air capacity are then altered. Fine particles can clog the soil, drowning or suffocating roots, while too large particles might lead to insufficient water retention and roots drying out. A balance between water retention and aeration is essential and an even finer tweaking can help with watering frequency.
Roots need to breathe, they need moisture, and the soil needs to be fast draining for both those things. There are too many mixes to go over, but pine bark and Napa 8822 don't retain too much water for a juniper to grow in. Too many people have been successful with it and not by chance. Perhaps the ratio or particle sizes are to blame if someone has had a bad experience with this mix with their junipers -- among many other confounding variables, e.g. tree health/genetics, environmental stimuli, fertilizers frequency and quantities, watering habits, human error and neglect.
Akadama, lava, and pumice has been used for some time -- tried and true -- yet more expensive.
As requested, a cost-effective alternative, a mix of perlite, pine bark, and calcined clay (Napa 8822) can be used to great effect -- also tried and true, as many have resorted to this mix over recent years.
In the end, experiment for yourself and make adjustments as needed.
They have 'soil wars' here. It's usually a hot topic.
That response wasn't aimed at the OP, rather the statement: "Be careful with 8822 in juniper or pine mix. It is water retentive - not liked by the species." It's simply not accurate.This is probably not helpful to a beginner asking a simple question for which there is a very simple answer. Everyone who’s been doing this for a while knows this can be as complicated as you want it to be.
Growing juniper and pine in 8822 (which I have done) is not advised. When I started, I grew everything in 8822... most of my pine seedlings kicked the bucket only a handful survived. All died from root related issues.That response wasn't aimed at the OP, rather the statement: "Be careful with 8822 in juniper or pine mix. It is water retentive - not liked by the species." It's simply not accurate.
That's insightful. It's always interesting seeing different and refined approaches based on experience.Growing juniper and pine in 8822 (which I have done) is not advised. When I started, I grew everything in 8822... most of my pine seedlings kicked the bucket only a handful survived. All died from root related issues.
I now use only as one part of an ingredient.
My current conifer mix:
1:1 Sifted Perlite and Sifted Saf-t-sorb or 8822 = (component 1)
then
1: 1/2 : 1/2 Component 1 to Crushed pine bark to pea gravel.
This for NJ 7b watering 1 time a day in morning.
For deciduous:
1:1:1/2 Component 1, Greenwaste compost, crushed pine bark.
Adjustments made for things like pot/container size, developmental stage etc. I also do use akadama as well for more advanced trees in place of 8822 or turface or as an added ingredient.
You hit the nail on the head. Great point.The real key is that anything can work if you water to the tree's needs.
I'd say 1:2 akadama to lava or pumice so it's the same ratio of akadama to whatever else as 1:1:1.If you’re going to get serious with bonsai get used to mixing your own soils. I’d go with a 1:1:1 like @yashu said, or a 1:1 akadama/lava.
It all depends, it is a good mix for propagation and for small (shohin) and smaller pre-bonsai, anything bigger (that will shoot a leader a few feet long) and you will have an issue with the wind moving the tree in the soil until its root ball becomes intact. I am using inorganic soil for my pre-bonsai, Monto Clay, Bonsai Block from Bonsai Jack and pumice. The advantage is that once I take the tree out of it I can rinse it, let it dry in the sun and re-use.Seems like for pre bonsai to just grow out a perlite and coco coir mix seems fairly popular
This is location dependent, if I use the traditional 2:1:1 the trees dry out too quickly requiring frequent waterings here in central Texas. I am using 100% akadama, 80/20 akadama:kyriu, or 80/20 akadama1:1 akadama to lava or pumice fine for deciduous
Good points. I also find it harder to tell when perlite is dry compared to pumice. I wish Pumice was cheaper as did pumice with a small amount of peat for some collected trees. They all seem to like it. I was originally using straight pumice but was worried would dry to fast so added peat to it for some retention.It all depends, it is a good mix for propagation and for small (shohin) and smaller pre-bonsai, anything bigger (that will shoot a leader a few feet long) and you will have an issue with the wind moving the tree in the soil until its root ball becomes intact. I am using inorganic soil for my pre-bonsai, Monto Clay, Bonsai Block from Bonsai Jack and pumice. The advantage is that once I take the tree out of it I can rinse it, let it dry in the sun and re-use.
This is location dependent, if I use the traditional 2:1:1 the trees dry out too quickly requiring frequent waterings here in central Texas. I am using 100% akadama, 80/20 akadama:kyriu, or 80/20 akadamaumice depending on how much the tree likes water.
Yea for deciduous I have also seen people use 100% akadama.It all depends, it is a good mix for propagation and for small (shohin) and smaller pre-bonsai, anything bigger (that will shoot a leader a few feet long) and you will have an issue with the wind moving the tree in the soil until its root ball becomes intact. I am using inorganic soil for my pre-bonsai, Monto Clay, Bonsai Block from Bonsai Jack and pumice. The advantage is that once I take the tree out of it I can rinse it, let it dry in the sun and re-use.
This is location dependent, if I use the traditional 2:1:1 the trees dry out too quickly requiring frequent waterings here in central Texas. I am using 100% akadama, 80/20 akadama:kyriu, or 80/20 akadamaumice depending on how much the tree likes water.