Substrate for Pre-bonsai- Do I need to sift potting mix?

Kahless

Kahless

Mame
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I'm going to be digging up and potting 50 of my trees that have grown in the garden. I would like them to continue to put on growth. I would use my bonsai soil (lava rock/pumice/DE), but lava rock and pumice are expensive. Pine bark is also hard to find around here unless it's reptibark. I put together a large tub of a mixture that I hope will be fine for growing out trees. It has potting mix with coarse perlite and some DE mixed in. Then I realized that the potting mix part of the mix is less than 3 mm size. Do I need to sift the fines out of this mix. That will be a majority of the peat moss part of it. Or do I just want to make sure there is enough larger particles mixed in to improve drainage? Also, is this the best cheaper mix I could be making for growing out trees, or should I just use mostly DE which is also cheap? Thanks!
 
You are going to have to be very careful with any kind of fine particles in the mix because it will retain a lot of water and could cause root rot.
Its better to go with a more open mix so that it drains well and doesnt stay sopping wet.
 
Alright, then I guess I can't use any potting mix for my pre-bonsai. I sifted the bucket to 3mm and that left mostly perlite and DE. I guess I should have just used DE. I'm just looking for the cheapest substrate to fill up 50 pots that isn't going to be terrible for the roots. I wonder if there is a potting mix that is a little chunkier?
 
Im pretty new but I learned something over the past year that was very important for MY setup. I almost killed a few trees with DE/Pumice mix, they just weren't staying moist enough with daily watering so I added about 20% potting soil to my inorganic mix and it helped tremendously.
Im not saying that it will work in your scenario but it was just something that clicked for me when I all I had ever read was inorganic substrate only.
 
I've read of some people using succulent mix because it drains much more freely. Not seen much on the results, though.
You can use organics in your mix, and do just fine with it. You just have to be careful about how you water.
I have many of my tropicals in a mix that includes oil absorbent, peat, coco coir, and even old coffee grounds. The peat and coffee help decrease the pH for acid loving plants, and will hold more moisture, as does the coco coir which also helps prevent things from compacting too quickly. More moisture is important for me, especially in summer when it's hot, dry, and I'm gone camping for 2 or 3 nights.
Just make sure your mix includes enough inorganic components to keep it draining freely.
 
Kahless said:
Do I need to sift the fines out of this mix. That will be a majority of the peat moss part of it. Or do I just want to make sure there is enough larger particles mixed in to improve drainage? Also, is this the best cheaper mix I could be making for growing out trees, or should I just use mostly DE which is also cheap?
Click to expand...
I think we are missing some important details. What size and type of container? What kind of trees at what stage? You mentioned “growing out trees”. If they are going into a plastic nursery can, then go to the local nurseries and see what they are using. The high quality ones are likely a loam, sand, and perlite mix. The shallower the container, like an Anderson Flat, the more free draining of a mix you will need. But as mentioned, pure DE will be tough for growing out trees since it will take lots of water and fertilizer since it has a lower CEC than organic particles. I used pumice, bark, and a quality potting soil component for my nursery cans in California. I didn’t sift it, since the cans had giant holes in bottom that I would cover with screen, newspaper, packing peanuts, or nothing. I haven’t sourced a new potting mix, but it will likely be a loam, sand, perlite, haydite mix.

Also tailor the mix for the type of tree. Some conifers like it drier and you could use a larger particle size. You can also refer to the below resource to dial in your water-holding capacity and air-filled porosity.

Introductory soil physics

Questions about soil physics come up all the time and I find that I repeat myself a lot on this topic. I'm going to try and write a reference for folks to refer to on this topic. I'm expressly NOT going to offer you any advice on what soil you should use in your garden, whether you should use...
www.bonsainut.com www.bonsainut.com

Good Luck!
 
hemmy said:
The shallower the container, like an Anderson Flat, the more free draining of a mix you will need.
Click to expand...
That's the important thing to keep in mind. Deeper pots are OK with finer mix because the depth helps with drainage and air filled porosity. That's why so many commercial growers can grow quality plants in soil mix most bonsai growers are horrified at.
Growing trees out in deeper pots is no problem provided you are comfortable with root pruning. Most species used for bonsai can be root pruned quite hard so no problems converting deeper root systems to shallower when the trees are ready.
After selecting a potting mix it is only a matter of adjusting your watering to suit the trees in that mix and pots.
 
Personally have used commercial Bonsai mix with good result. Presently add more pumice to personal pre/developmental conifers😉.
 
Ive never sifted anything, I find that most debris just washes out with watering. I often mix potting mix in with cat litter, especially with trees in training in training pots, because its cheap and it works for me. as long as it drains freely and quickly. ill just adjust watering accordingly, since its a moisture retentive mix as in, where most will water 2-3 times a day in summer, I might only need to do it once or every second day for example. depends really.
most species I work with love a drink and hate being even a little dry.
 
Thanks for the replies. I will stick to deeper pots with a mix of potting mix, perlite, and DE, and root prune to promote a flatter base. I aim to water once a day and it's pretty dry here.
 
Kahless said:
Thanks for the replies. I will stick to deeper pots with a mix of potting mix, perlite, and DE, and root prune to promote a flatter base. I aim to water once a day and it's pretty dry here.
Click to expand...
One more thing to add, just drill lots of holes into the bottoms of your containers so the water always has many routes out, evenly around the pots.
 
Just had this thought. We'll see if it works for you.
@hemmy posted a link to the soil physics resource. Very informative, I highly recommend. Once I learned a bit about the concept of perched water table, I've actually used that to try creating a sort of simulated shallow pot without having to actually use a shallow pot. I filled the bottom with large lava rock, like landscaping size, and put my tree and regular substrate on top. Unfortunately those couple of trees I tried this on didn't make it through last winter, so I can't tell you for sure how it worked, but in theory this should be the compromise between the benefits of deep pots and shallow as far as root growth, and aid water retention in substrate that has problems in that area.
 
ShadyStump said:
Just had this thought. We'll see if it works for you.
@hemmy posted a link to the soil physics resource. Very informative, I highly recommend. Once I learned a bit about the concept of perched water table, I've actually used that to try creating a sort of simulated shallow pot without having to actually use a shallow pot. I filled the bottom with large lava rock, like landscaping size, and put my tree and regular substrate on top. Unfortunately those couple of trees I tried this on didn't make it through last winter, so I can't tell you for sure how it worked, but in theory this should be the compromise between the benefits of deep pots and shallow as far as root growth, and aid water retention in substrate that has problems in that area.
Click to expand...
it doesnt matter much if you start with a shallow or deep pot, whats important is that you do regular root pruning to achieve the results you want. Shibui has pointed this out many times.
the shallow training pot is even less important if you start with plants that already have good nebari.
 
BobbyLane said:
it doesnt matter much if you start with a shallow or deep pot, whats important is that you do regular root pruning to achieve the results you want. Shibui has pointed this out many times.
the shallow training pot is even less important if you start with plants that already have good nebari.
Click to expand...
Not wrong, but if you're growing out saplings, or trying to fix poor nebari, it can make the difference between the issues inherent in frequent repotting and decent healthy tree in short order.
Different people find different techniques beneficial in different circumstances, and I was just sharing one I've toyed with.
 
I bought a shifter and used it once , don't really bother with it as the soil mixture that I use is adequate
Think it maybe another item you will be collecting and putting eventually putting on the shelve
😁
 
I use my sifting screens every time I mix soil components. From the amount of dust I get out of some bags, I'm glad I have them.

As Hemmy reminded me in the next post, they are also useful to sort soil for size for shohin or smaller trees
 
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