A lot of problems occur that are linked to inadequate soil mix. Most of the time, overwatering and a soil mix staying damp that leads to root rot, and since the tree is weakened, various diseases. Just like when a person is weak, they get any virus or disease that is around. The issue is particularly significant for potted trees. Here are a few basic rules from my experience in my "environment": 1/ healthy trees have roots that must get water, and air. A healthy soil has about 40% of "void" (that's what a university teacher, a specialist of soils told us). 2/, 3/, 4/ etc. are irrelevant if 1/ is not respected. So, a good mix is a free-draining mix (air), but it must retain some water too. The smaller the soil particles, the worse it is. (To be continued)
2/ A good soil mix needs good fungi, good bacteriae, and good "animals" (in French "mésofaune"), some of these microscopic : the latter help the soil to keep aerated. Overwatering kills a lot of these. Just like a persons drowns. Fungi : most plants are associated with fungi that help them take the nutrients thay need. A soil that is too damp keeps them away. Look at the "mummies" found in marshes or peat that have been discovered, or the stone-age dwellins in the river Thames. The lack of oxygen (anaerobia) kept them if not pristine, at least in a very good condition after hundreds of years. (to be continued)
But a good soil mix of course depends where you live. Here, we have more and more hot and dry summers. Here's my basic mix for potted trees: Pozzolan 5-7 mm (50%) Composted pine bark (30%) (I must water from the hose and the water is very "hard" here) Pumice 5-10 mm (10%) Pine bark chips 5-15 mm (10%) For my bonsai, depending on the species, I use pozzolan, composted pine bark, and between 20 to 70% Akadama. What about you ? What is the soil mix that works the best where you are ?...
My mix is John Innes no 3, Peat, horticultural pine bark, and horticultural potting grit. This then has food for the roots, and slightly acidic, plus water retentive capabilities, loose and light with the pine bark and grit to allow extra air to circulate. Everything that a maple needs. The one bonus with this is also price. Here Akadama, Pumice and Lava rock is at exorbitantly silly prices. If you have a lot of pots to do each year, cost is important. So thats mine......
I always seem to over complicate things, my latest concoction is, 2 parts ericaceous, 2 parts composted fine bark, 2 parts coir, 2 parts potting bark, 1 part perlite. I only came up with this recently and haven't really used it yet, well where I have its too soon to tell, so any ammendment suggestions are more than welcome.
Do you know N, we all seem to have a concoction of soil mixes that work, but as can be seen by yours and others on the maple forum. They are all basically the same. Nutritious, 'slightly' acidic and very open, allowing air to circulate and drain freely. I used to have friends who had the most beautiful maples, and who were so secretive about what they put in their mix, it was ridiculous. Nowadays with great forums as the UBC, we can share all our methods with each other. 'No secrets'...... well I hope not.. lol.
I like to use a lot of bark and some perlite and grit/gravel to open up the "wet" ingredients. I don't have an exact recipe but usually use some hind of store bought "multi purpose compost" as the starting point which is usually a blend of peat and other ingredients. Then I add a little John Innes (a loam based mix for those not in the UK) and the aforementioned bark, perlite, grit etc to open out the mix. Sometimes I substitute ordinary garden soil for the John Innes. I will put an old pic below of what my mix looked like in 2011. Slightly off topic but I find the pricing of perlite in the UK to be very strange. All of the shops I have been to have a maximum bag size of ten litres and this costs about £9 - nearly a pound a litre! However if you go on Amazon (or other websites) you can order a hundred litre bag for about £21, which, when you work it out, is close to a fifth of the per litre price compared to the shops.
I ordered the amazon one then due to the courier damaging the package I ended up with two, so I now have a lifetime supply. Lol
I use nothing but Turface MVP (a U.S. brand of high fired Montmorillonite clay) for just about everything I grow. I'm a KISS* fan. I like my scotch neat. I'm don't care much for mixed drinks either. But to each his own. I do like Bourdeaux wines. I'll note that I now grow my potted pines in pumice instead. I do so because I could not teach myself to not water them as often as everything else in my bonsai garden. It is nearly impossible to have a large enough grain size Montmorillonite clay, but this larger grain size is very easy for me to get a as pumice. In my case, the primary point of larger grains is a lowered level of substrate saturated with water. After watering the substrate/mix/soil is saturated with water up to some level = the saturation level. Every species will tolerate their roots being underwater for a brief period of time. How long this saturation remains is largely determined by how rapidly the tree's roots can adsorb the water and have it moved out, through the tree, by transpiration. Maples are very good at this, so I keep my maple bonsai in pots that are only an inch or so deep. Pines, on the other hand do not do this at all well and roots tend to drown even in pots of Turface that are even 3 or 4 in inches deep, with my watering habits (that are attuned to maples). I want my life to be simple and not need to go through soil analysis of every one of the 100+ trees in my collection when I water. I need a lager grain size substrate for pines. Were it possible for me to have quarter inch-ish grains of Montmorillonite clay, that is what I would be using, but grains that big are only readily available as pumice. So I now grow my potted pines in pumice. They are now healthy and my daily life with my collection is simple. *Keep It Simple, Stupid.
Thanks for posting, very interesting OSY I used to tell my pupils "Keep It Super Simple". Two sides of the same coin I guess ;-)
I usually do 50% Pumice and 50% Pine bark for some of my pots. 50% Pumice and 50% Akadama on some of my other pots. Still trying to experiment to see what works best for me and my zone/area. I don't have composted Pine Bark(I'm composting some) but I'm supplementing those with fertilizer since I heard fresh Pine Bark saps Nitrogen. For the ones I planted on the ground I use acidic soil that's usually for Azaleas and mix half of it with my native soil which is a bit alkaline. For Fertilizer I use Osmocote Plus.
Sounds like a very good mix @Anj, I do agree that it is important to experiment for the area you live. Sometimes one size does not fit all, as the saying goes...
30% melcourt small pine chips 30% melcourt composted pine bark 20% Ericaceous Compost or other compost 20% sharp sand and horticultural grit mix - sometimes just the sand if I have no grit I seem to have used a whole one ton sharp sand builders bag over the past 4/5 years lol it was left over from a building project and was sat in the rain for 5years before I started using it ..I think this washed out any salt etc..whilst this has worked really well I won’t chance using building sand going forwards