Seed and seedling soil mixes

[Ryceman3]

Just doing a bit of research into what soil mix to use that will give me the best chance of germinating seed (mostly pines and a couple of other species) this coming Spring. Also thinking of the possibility of the same/similiar mix for pine root cuttings ... should I get that far and feel adventurous.
I have thought about incorporating vermiculite ... most likely with coir peat (see image for a relevant page from a supplier's brochure). I know others have said to steer clear of this for standard bonsai mix, but wondering if anybody has any experience using it on seeds/seedlings and whether it translates in real life as positively as the brochure suggests!
Any advice (good or bad) would be appreciated.

[Starfox]

I use a mix of perlite, vermiculite and coco fibre generally and it seems to work really well. This year I have not been able to find any vermiculite and my mix seems heavier. It still works ok but I would add it if I can find it. I roughly measure it out in to thirds.

Not really tried it on cuttings yet but can't see why it wouldn't be any good.

[shibui]

Vermiculite is Ok for short term mixes such as seedling mix but it does break down so I guess that's the reason for not using it in bonsai mixes where the tree will be in it for a number of years. When I worked at a production nursery we used vermiculite sprinkled over the seed trays after sowing to keep tiny native seeds moist while they germinated.
Don't think that vermiculite is magic, even though the adverts sound really good. It is just an inert material that can absorb moisture and has rough sides so allows air penetration as well. There are lots of other materials with similar properties.
I usually use my normal bonsai mix with the coarser particles sieved out for smaller seed and any seed as large as pine seed goes into the same mix I use for the bonsai.

An inert mix like the coir/vermiculire is generally reasonable free of pathogens for a start so can have some benefits when sowing really hard to germinate or very slow growing species but most common species are very hardy and should grow well in any good potting mix. Remember that these trees have ben germinating for millions of years in ordinary soil in the forest and managing to survive. Any mix will gradually become contaminated with fungi and other diseases but most healthy seedlings should be able to resist.
I think the biggest challenge when growing seed is not getting the seed to germinate, rather stopping the seedlings from getting infected and dying after germination. Damping off is one of the biggest killers of young seedlings. Try to keep them slightly on the dry side and allow plenty of fresh air and sunshine, both of which help deter fungal diseases.

I have never seen a pine root sprout but I have also not tried growing pine root cuttings either so best of luck with those and let us all know if it works.

[Ryceman3]

Thanks both Starfox and Shibui for your feedback. Always good to hear from those who have first hand experience. I feel like it may be worth a try and your response helps confirm it for me Starfox.
Shibui, I think my idea would be to use the vermiculite/peat mix in combination with a more conventional bonsai soil mix around it, so as the seed/cutting develops roots extend and “graduate” to my regular mix essentially. Does that make sense? When I say root cuttings on pines, I mean the technique where after a seedling establishes, the stem is cut from the roots so new roots develop further up the “trunk” of the potential tree... as opposed to the traditional root cutting. Not sure I made that clear at all so apologies for any confusion. I appreciate the info in relation to keeping seedlings viable after germination, very interesting and much appreciated info all around!

[shibui]

Seedling cuttings of pines are quite reliable and simple. I got almost 100% success while I was trying it over a few years.
Only a small proportion of seedling cuttings actually make a good radial root system. Quite a few just put out one or 2 roots and are no better than ordinary seedlings and the process takes a few months so development is slower.
In the end I found that I could get roots just as good by pruning the existing root system and no setback or delay while the cuttings made roots.

I usually prick out pine seedlings very young and root prune to get better roots so no need for roots to graduate from seed mix to potting mix. They go straight into potting mix after root pruning. Some pictures of this in this thread - viewtopic.php?f=9&t=24852&hilit=+pine+seedling in case you'd like to try another possibility.
I have also been taking cuttings from young seedlings. That gives me 2 trees from each seedling - the lower part grows low branches because it has been pruned and the top I have cut off grows roots as a new plant. The previous thread also shows how I prune the seedlings and make cuttings of the juvenile growth that is cut off.
This thread shows the cuttings with roots and potting them up into individual pots - viewtopic.php?f=9&t=14454&hilit=+pine+seedling

[Ryceman3]

Thanks once more for the links and an explanation of your experiences Shibui, very interesting reading ... particularly the cuttings from seedlings, an inspired idea!
I’m sure I’ll read over these threads a few more times in the coming months.

[dansai]

I've only ever used the potting mix I use for general growing on for seed sowing. I place some in a pot or seed flat, firm it down a little, sprinkle the seed on then cover. I will cover the seed to approx. 1 & 1/2 times the seed thickness with potting mix with larger pieces removed for small seed. I've germinated very fine native seed, pine seeds and up to large Cycad seeds the same way with good success. The pots seems to work the best for me as seed flats seem harder to keep evenly moist without more attention than I can give.

We used vermiculite at TAFE as a top dressing over the seed with the seed on a seed raising mix. The seed rising mix was just the same as the potting mix that had been sieved and had more sand added. We only ever used it as a top dressing as it crushes very easily and so in a mix causes compaction/aeration issues.

[treeman]

Currant best practice for seed raising mixes these days seems moving away from fungicides etc; and using mixes with highly pathogen suppressive properties.
I will elaborate more later as I'm being called to go for lunch

[treeman]

So the suppression of pathogens in potting mixes comes from the level of microbial activity in them and time the microbes have had to balance their environment. (this is probably why damping of almost never occurs in natural forest systems) Apparently some materials seem to give higher and longer lasting suppression. In the past I have lost seedlings from damping off in off the shelf seed raising mixes. I have since discovered that adding 10 or 20 % of suppressive media usually protects the new seedlings without further treatment. Unfortunately it's difficult to know if your mix is highly suppressive unless you make it yourself. Many bark based potting mixes for example are only mildly suppressive and for a fairly short time. One way to increase the lasting quality of this property is to add a composted material which has been allowed to mature for several months to one year or more. I happened to have some left over municipal mulch which was left to sit there for more than 3 years. It was made from typical garden refuse, leaves, stems, bark from a wide range of trees and shrubs. A lot of it was broken down so much that there was a large amount of fine humus as well as tiny bits of dark, completely consumed wood materials. After sifting out the dust and the courser material and adding water and bagging it (I got 12 bags!) I noticed a few grass seeds germinating through it. I then tried to germinate some very rare epiphytic cacti seeds from Holland in it. (after adding sand). (Normally this type of precious seed is sown in steam sterilized mix to be absolutely sure it is free of pathogens and also treating the seed itself) Anyway, all seeds germinated well and are growing well in this material even though it had been laying on the ground for 3 years. This shows that it is a well balanced and perfectly mature mix with highly suppressive microbial activity.
Long story short, If you can get hold of some of this type of material and keep it sitting in a heap for an extended period, chances are you will end up with the best seed raising mix possible. You can plan a year ahead and make a compost pile of sawdust, cow manure and grass or leaves and let it sit there moist and well aerated (by turning it over every once in a while) and using it after it has thoroughly decomposed. This is vital. Adding wood seems to be an advantage because the decomposition keeps going for a long time and may have something to do with the fungi species doing the decomposing? It has also been found that bark from hardwood trees gives very good suppression compared to softwood bark. In WA they use various Euc bark without any composting or pre-ageing and found it to be highly suppressive for several years. Adding just 10% of this kind of material will impart suppressiveness to the rest of the mix as well!
You can never really be sure how suppressive your mix is by buying it in bags. It may be very good or it may be very dodgy.
Too much information?

Maybe not enough! https://scholar.google.com.au/scholar?h ... +materials

Just as an aside, The latest examinations of out own gut microbial populations is also finding similar results. We can think of our gut and it's microbes as our version of the soil environment for roots. Apparently it's the microbes in our large intestine which govern the health of our immune system just as certain microbes can boost the immune systems of plants.

[shibui]

That's all very interesting Mike. I'll need to do some trails and see what occurs up here.
For anyone thinking of adding wood to a potting mix you need to remember that wood ties up nitrogen as it decomposes. Well composted wood/ sawdust, etc is a bit better as it has had some time to start breaking down but it will still be taking some N from the media around it and plants growing in such mix usually show N deficiency unless you feed regularly to counteract the loss of available N. Fresh wood products are usually even worse.

Epiphitic cacti are usually a bit more tropical. No wonder the Dutch ones are rare

[Ryceman3]

I've only ever used the potting mix I use for general growing on for seed sowing. I place some in a pot or seed flat, firm it down a little, sprinkle the seed on then cover. I will cover the seed to approx. 1 & 1/2 times the seed thickness with potting mix with larger pieces removed for small seed. I've germinated very fine native seed, pine seeds and up to large Cycad seeds the same way with good success. The pots seems to work the best for me as seed flats seem harder to keep evenly moist without more attention than I can give.

We used vermiculite at TAFE as a top dressing over the seed with the seed on a seed raising mix. The seed rising mix was just the same as the potting mix that had been sieved and had more sand added. We only ever used it as a top dressing as it crushes very easily and so in a mix causes compaction/aeration issues.

Thanks Dansai, some good practical knowledge in there, the pot vs seed flat bit was interesting. Thanks for your input.

Too much information?

Maybe not enough! https://scholar.google.com.au/scholar?h ... +materials

Thanks treeman ... detailed as always!
Unfortunately I don't have the garden/outdoor space to compost pretty much anything so I'll have to make do with what I can source, but I did do a bit of reading from the link you gave in addition to your post - it was interesting stuff. Essentially what I took from it was summed up in the term below ...

soil.jpg

which ties in with what you said here ...

So the suppression of pathogens in potting mixes comes from the level of microbial activity in them and time the microbes have had to balance their environment. (this is probably why damping of almost never occurs in natural forest systems)

and Shibui mentioned here ...

Remember that these trees have ben germinating for millions of years in ordinary soil in the forest and managing to survive.

I've still got a bit of time until I need to sow, so I'll keep mulling over my options. I most likely will trial a few different things and see if I can figure out what works best for me ... but essentially I should just remember what I'm trying to do is get a seed to germinate and grow a healthy seedling, which is the same goal that the seed itself has (assuming it's viable) so it's probably best not to overthink it!

[treeman]

"

shibui"
For anyone thinking of adding wood to a potting mix you need to remember that wood ties up nitrogen as it decomposes. Well composted wood/ sawdust, etc is a bit better as it has had some time to start breaking down but it will still be taking some N from the media around it and plants growing in such mix usually show N deficiency unless you feed regularly to counteract the loss of available N. Fresh wood products are usually even worse.

That's very true Neil. Given enough time however, the N becomes available again when most of the material is very well decomposed. Probably from the dead microbes which make up a good percentage of humus. The stuff I used was probably 50% humus and the rest made up of slightly larger more resistant bits of wood. Although the particles where still intact you could easily grumble them into dust between your fingers. I have not noticed any nitrogen draw-down in the seedlings growing in it. I guess that's where the maturity of the material comes into the picture. Less mature compost would certainly need added N - at least shortly after germination.

Epiphitic cacti are usually a bit more tropical. No wonder the Dutch ones are rare

Ha ha. Yes actually from Brazil originally.

[treeman]

Here's the material I was on about

P1120263.JPG

Here's one of the intact particles

P1120266.JPG

Here's the same particle crushed showing just how decomposed it is.
This stuff seems to be gold for seed raising!

P1120267.JPG

And here are a few of the cacti seedlings growing in it. As you can imagine they are pretty susceptible to rotting off but no such problems here.

P1120277.JPG

[shibui]

I notice that you have only half filled the seed pot. Is that your normal approach or just for these cacti?
I have been told to always fill the container because half full pots create dead air pockets where fungi thrive. Seedlings growing at the rim of the container get better air circulation and should be less prone to problems.

[treeman]

I notice that you have only half filled the seed pot. Is that your normal approach or just for these cacti?
I have been told to always fill the container because half full pots create dead air pockets where fungi thrive. Seedlings growing at the rim of the container get better air circulation and should be less prone to problems.

The dead air pocket sound like a bit of a myth to me, but either way it doesn't matter in this case because they are placed in sealed zip lock bags and left there until well after germination, sometimes for several months without the need to open. Normally I would fill the pot for tree seeds etc., not because of the dead air but more for access to light. In this case I don't want to much root room as the root systems are slow and weak compared to trees.