Not sure but I think there might be a bit of misunderstanding. I have never found containers - especially large containers - to be inhospitable to the soil food web. Never read that it is either and would have to disagree with that claim.

Rather the issue is that a soil food web is not there naturally as it is in the ground. You have to add it for most organic fertilizers to be effective in containers. They have given it a good start for you with the addition of the myco. So much so that one now finds other bagged mixes to be copying them. :).

ProMix BX is by far the more common of their mixes used. It is their all-purpose mix - excellent for both seed starting as growing on straight out of the bag. The ProMix HP is high-porousity due to more coarse textured perlite and is recommended for water-sensitive crops and for rooting cuttings. Also good for those who tend to consistently over-water as it drains much faster than BX. For example, I have found it good for peppers as they prefer to dry between waterings as opposed to tomatoes that prefer consistent soil moisture levels.

But they both have the same added myco and its presence allows for the use of organic fertilizers IF you are so inclined. But yes, the plants will still need to be fed in some fashion. How you feed is your choice - no harm/no foul.

It is blended for use straight-up - as is, no additions required and that is how most use it. It is pH balanced to 6.5. Already contains the needed lime, Can you add compost? Sure if you wish, understanding it will slow the drainage. Can you mix in some 5-1-1? Again if you wish but it isn't required and would tend to nullify the benefits of both mixes. Add more perlite? If you wish but it isn't required and will only increase the drainage.

it consists of like 75% sphagnum. Not the best word in the world when hearing some of you talk about container mixes, especially at that ratio.

I understand what you are saying. It is different from 5-1-1 - very different. But it doesn't necessarily follow that is is bad. BX is considered to be one of the nursery industry standards. Does that mean it is better or worse than 5-1-1? No, just that it is a different. They both work well IME and while the use of ProMix and similar mixes is far more common than 5-1-1, only you can determine which may work better or worse in your particular garden and situation.

Hope this helps.

Dave

Thanks Dave!

I agree about Large containers being able to support a microherd. I've just heard it on more then one occasion that trying t maintain one in containers can be challenging.

Regarding the compost. Wouldn't you want SOME organic matter for the micros to feast on?

Regarding the lime. So, the plants will get the Ca and Mg needed? Will adding bonemeal give them TOO much Ca?

What about this? You say the compost will affect drainage-- what if i add some compost and then some more perlite to offset that difference? Thoughts?

Mixing with 5-1-1. You say that would nullify the 2 media's features. Explain please. Is it a matter of one being an almost hydroponic medium(5-1-1) and you want the structure to hold up for years? And by adding the myco, the bark would be broken down quicker?

One last question -- you say the BX is excellent for seed starting. How about peppers? Most of us in the hot pepper forum are under the belief of using mixes low in peat. Have no idea why, but the "experts" say try to stay away from it. Is it a water retention thing, you think?

Once again, thanks for all the help. You're one of my trusted "go-to's."

Kevin

I should have qualified that I mean big containers - say 20 gallons and up for purposes of discussion - as i would agree it is impossible in "pots". And I'll add that I don't agree with the creative math that some use to argue that a 12" pot holds X gallons of potting mix.

Regarding the compost. Wouldn't you want SOME organic matter for the micros to feast on?

Yes, I would if I was using organic fertilizers for those containers. They would need more than just the fertilizers themselves to eat.

But I don't use organics in containers so feeding the myco more than just the peat isn't really relevant for me. But if i was I would mix it in lightly several times through the season, not all at once in the beginning. And I'd use compost teas to feed too like I do in the gardens.

Regarding the lime. So, the plants will get the Ca and Mg needed? Will adding bonemeal give them TOO much Ca?

Bone meal, no use. Takes far too long to have any effect. Might help the following year but not this year. Ca and Mg enough? Theoretically, yes. But as you know that also depends on the type of plant needs, weather, which fertilizer you are using - does it contain added CA and Mg? - how often you have to water and flush them, etc.

My fertigation supplements for containers contain both so the lime as is is sufficient. If I was only using organic supplements then I'd make sure to use one with added micros. Does that mean you can't add more lime? Not t all. I know Raybo adds it to his earthtainers and Earthbox recommends adding it too so clearly it is an available option. Problems would be how much?

What about this? You say the compost will affect drainage-- what if i add some compost and then some more perlite to offset that difference? Thoughts?

It will retard drainage if used in excess. So as I said, small amounts mixed in like side dressings several times through the season would seem to be a better approach. Clearly an option but again how much additional perlite is enough? How much is too much? It's like experimental cooking which has never appealed to me. I want to know up front it is going to be edible. :)

You say that would nullify the 2 media's features. Explain please. Is it a matter of one being an almost hydroponic medium(5-1-1) and you want the structure to hold up for years?

In part but it is the competing textures i see as a problem, not the presence of the myco. Mixing the two would cause the 5-1-1 to compact much more and the whole point of using it is preventing compaction and insuring drainage. The ProMix is not normally considered a multi-year mix like 5-1-1.

It is sort of a bananas to oranges comparison - both are tasty (work) but they taste (work)very differently. Mix the two and all you get is fruit salad. They have different structures, different porosity, require different watering regimens, different decomposition rates, etc. One can easily compare them in containers side by side but trying to mix them in the same container with the idea of improving both just doesn't fly IMO.

All of our pepper plants in the nursery are started and grown in ProMix. Another close friend and business competitor prefers using Metro Mix 360 (another industry standard) which is similar in terms of peat content. Can't comment on the guys on the Pepper forum.

Dave

Kevin - I haven't had any problem starting peppers in a peat-based mix, though I haven't used ProMix for that in 3 years. I did just buy a bale of ProMix this year, am starting my determinate tomatoes in it since I ran out of Fafard & Espoma mix I used for peppers and indeterminates (Espoma was heavy so I mixed in more perlite).

If your water's pH is that high, I would not add lime to the mix.

Funny Dave mentioned organics not working in smaller pots, but 20 gal or so could mix in compost esp. if using a mix with the myco in it. There was an article in out local online newspaper (I'm sure it's all across the country) about growing greens in containers and the author recommended Milorganite. I'm not going to get into what I think of them calling that "organic" and its suitability for vegetables, but I commented that unless you had a really big container (I said 15 gal) and had used such a mix and/or compost to get the microherd going, any organic fertilizer wasn't going to do much. My comment was deleted without notifying me.

MILORGANITE in containers?!? MILORGANITE to grow edibles?!? GROSSSSSSSSSSSSSSS!

Thanks All.

Dave: obviously seed starters are using it for components and not so much for the myco.. because we already determined that small containers are useless for microorganisms, right?

Also, so only 1 year with the stuff? Reasons?

Thanks again. lol

Kevin

Also, so only 1 year with the stuff? Reasons?

It's no different that any other peat based potting mix in that regard be it MG, Sta-Green, Fafard, Fox Farm, Metro, Sunshine, etc etc.

They all decompose, compact, porosity is lost, etc. over the season. That fact is the whole basis for Al's 5-1-1 as an alternative. Some will get 2 seasons out of them by recharging the mix - 1/2 used mixed with 1/2 fresh. They also make great in-ground garden amendments after use.

obviously seed starters are using it for components and not so much for the myco..

Basically yes although there is some myco root colonization on the seedlings that benefits then while still seedlings and then carries over to the garden when transplanted. But its primary or long term benefit IMO is it allows for the use of organics in containers.

Dave