Does Seedling Substrate Matter?

[QuantumSparky]

I've seen countless posts/articles/guides about how to root cuttings or transplant seedlings and what confuses me most is the wildly different types of substrates people recommend.

One person will say potting mix, another will say peat, another will say straight Perlite, and then there is...sand??

These are all so different and I can't figure out what makes one better than the other. I thought plants take nutrients from the medium that their roots are growing in, how the hell does sand or perlite work then?

 

[Tidal Bonsai]

I have never had good luck rooting conifers, and to be honest I am not that interested in figuring it out. However, I have rooted hundreds of deciduous cuttings. I used Jiffy seed starting mix because it was what I had on hand the first time I tried, and I never had a reason to change.

I have seen people use any number of different things, don’t overthink it.

 

[RKatzin]

Substrates do matter, but not as much as how and more importantly, when you take cuttings or sow seeds.

 

[leatherback]

some substrates are convenient for fungi to grow in and/or tent to stay very wet. Mostly organics come to mind. THis can cause damping off and/or rotting of cuttings.

Mineral substrates do not have nutrients. True. Which is why not much lives in there. There is nothing to be had. So that gives support to growing you and/or weak plants.
Once rooted one of course have to fertilize, just as you need to fertilize bonsai.

 

[sorce]

There are tradeoffs for every choice.

I prefer good root system creation over vigorous growth.

Until a good root system is developed, you stand a greater chance to have a "take off runner" that ruins the design on the bottom or the top.

Sorce

 

[QuantumSparky]

There are tradeoffs for every choice.

I prefer good root system creation over vigorous growth.

Until a good root system is developed, you stand a greater chance to have a "take off runner" that ruins the design on the bottom or the top.

Sorce

Can that really ruin a design so early in the tree's development? Surely the structure doesn't matter much at that stage

 

[Tums]

Can that really ruin a design so early in the tree's development? Surely the structure doesn't matter much at that stage

I was growing out a viburnum under a foot tall at the beginning of the year. I must have over-fertilized it and the internodes are several inches apart. I kind of consider that one ruined for bonsai because there's hardly anything to cut back to for low branching, so it'll go into the yard now.

 

[QuantumSparky]

I was growing out a viburnum under a foot tall at the beginning of the year. I must have over-fertilized it and the internodes are several inches apart. I kind of consider that one ruined for bonsai because there's hardly anything to cut back to for low branching, so it'll go into the yard now.

Does that happen because the growth is so fast on too much fertilizer that you get a ton of stalk before you get more buds?

 

[Tums]

Does that happen because the growth is so fast on too much fertilizer that you get a ton of stalk before you get more buds?

I got big leaves and big internodes to go with them. (edit: and yes, the plant is significantly taller now)

 

[leatherback]

I got big leaves and big internodes to go with them. (edit: and yes, the plant is significantly taller now)

cut back to where it started to take off and the summer growth will be more condensed. I find spring growth often is good for health and thickness, summer growth for design.

 

[sorce]

Can that really ruin a design so early in the tree's development? Surely the structure doesn't matter much at that stage

In studies of tops and bottoms, it is evident that tops and bottoms will, under perfect conditions, be exact mirror images of one another.

Enter the impossibility of perfect conditions, and we can see why it is not always evident.

The impossibility of perfect conditions is what we are allowed control over. So though there are a million possible ways things can go, consider this one scenario as an example.

If you dig a seedling and it has one stronger root, that, if placed in anything but a rootpruning container, will be allowed to grow uninterrupted as a mirror of one strong shoot above, it's this root that lopsides a nebari, which is your "ruin of design" at this stage.

It is taught to "let the top grow unimpeded" too, which is wrong and impatient, since cutting it back, will stop that one strong top shoot and bush it out, which, in theory, should be mirrored below. Again, conditions won't be perfect for the bottom to also bush (read, radial nebari), but it gives us a better chance for it to. Where leaving the top runner run will almost certainly lead to a lopsided nebari, especially in a "regular pot".

Once your bottom is in a state of like 80% good close feeders, it becomes nearly impossible for the tree to revert back to growing long thick roots that ruin nebari, because it knows it is receiving everything it needs from what is present.

So top structure should be ignored in favor of bottom structure first. When your bottom is so wonderfully ramified, your top will only want to follow suit. And you will have every bit of vigour to build anything you want on top.

So we must be aware of top growth, but short a straight 1ft section of internode that will never bud leaving the soil, it hardly matters what the top is doing. Even then, you could graft a low shoot and continue on.

The condition of how we control top growth is quite dependent on tree habits. Alternate, opposite, conifer, D, "won't backbud", only backbuds at nodes, backbuds anywhere, healing rates, etc, should determine the state we have the tops during the initial period of rootsystem formation.

Sorce

 

[leatherback]

in theory, should be mirrored below.

Personally, I have never seen any proof that this really is happening tbh..

 

[Wires_Guy_wires]

In general, I don't like inorganic substrates for seedlings.
Because seedlings want to make taproots, which are hard to remove and a pain in the butt to deal with. So prevention is wise.
I use organic soil for seedlings to make that happen. It comes with the risk of staying too wet for too long, dampening off, fungal issues, but it prevents me from manually killing my seedlings in their first transplant because that darn taproot needs to be removed.

For germination however, I prefer inorganic. Fewer fungal issues, way better water control.

What makes a good substrate is you. Cocopeat/choir for instance is awesome! It's the middle ground between inorganic and organic, but I just can't deal with that stuff. I'm from a potting soil household and I was raised a potting soil boy. I know how it works, how to water it, how to keep it healthy. And that just doesn't work for everyone.
There are so many possibilities because there are so many people with so many preferences. The key is understanding your goal, understanding your own style, and finding a middle ground. Experiment, go wild! Make blends, throw in some sand, use some sphagnum, try rocks.. Just stay away from garden dirt and compost.

Especially seedlings have those first leaves that are packed full of starch. So they don't need much nutrients at the start. Sand can hold some, potting soil excretes it, inorganics can hold some too, the key is finding out when to fertilize (or not at all!).
I have a personal philosophy of "Bad conditions first" because it forces plants to stay small, internodes short and their health always at a tipping point. Growth output doesn't matter to me in the first years, I want silly putty in the future.. Something to work with. So with that goal in mind, best keep them small so the buds will stay low to the ground, new shoots will stay close to the ground, and that stunted and contorted growth benefits my design later on. This is a terrible philosophy for beginners because you can lose your entire batch in a week. But the ones that make it are perfect for bonsai. They're strong, vigorous, resilient. Just what I was looking for.

There is no absolute rule, it's just fun and games. Experiment, learn, evolve! Whatever you try and however it turns out, it adds to your base of knowledge and your understanding of soil dynamics. Don't trust the people on the internet! They're not the ones holding your watering can or chilling in your garden. If you can pull off coco coir, I'll take my hat off for you. If you can do potting soil, welcome to the team. If you rock those inorganic rocks, sweet!

 

[Shibui]

So much depends on the strength of the species, location, care and how many of the seedlings you expect to survive.
What works for one species in one instance may not work for a different species or in another location or with slightly different care. Hence the differing experiences and views of what is 'right'

Many strong trees and 'weedy' species can survive almost anything. Someone with experience growing these will have much different advice than another grower who is trying to grow rarer and harder to grow plants.

Pines I have tried and many larger seeded species will usually grow despite the potting mix. Smaller seed trees don't have the same reserves of energy so they tend to need conditions just so to survive.
Also remember that different species occupy different ecological niches in nature and are adapted to survive in different soil types or conditions so no one set of circumstances will suit all different species. You may need to research what conditions suit each particular species.

General potting mix and garden soil is alive with microbes - good and hostile. Susceptible species can sometimes overcome the pathogens but will often be affected and sicken. In nature this is offset by the huge numbers of seed produced every year. Even if only one survives to maturity balance is maintained but we expect better than that.

Seed raising mix has been sanitized to reduce pathogens. Inorganic mixes are naturally more free of pathogens so these are more likely to give better results with less robust species. and, of course, stronger species rarely object to an easy start to life either so using purpose made mix should always give better results.
Generally seed has an inbuilt store of energy. Enough to get the new seedling started until it can find nutrients of its own so seed can germinate in nutrient poor sand or perlite and still grow for a few months on stored nutrient and energy. If you want them to survive for longer you'll need to transplant into nutrient richer soil or start feeding with fertilizer.

Always remember that posts and articles usually reflect the personal experiences of one grower in one place and often very limited experience so they rarely give a good overview of the subject. Always expect different points of view when dealing with living things as the same plant can react very differently in different areas or with different care so general rules are rare.
Have fun trying different things until you find something that suits the species you grow in your area. Some failures are just part of the process.

 

[Lumaca]

I've tried to grow JBP in various medium, but damping off always claims all in organic soils.

Other trees, tropical trees, I've grown in anything I can find and 9/10 survive just fine (coir, peat, rice hull, charcoal, manure). My conclusion is that there are resilient trees and delicate trees. In my humid weather (between 60-95%), fungal issues is a huge concern so my JBPs are now in fully inorganic.