That is a tough assignment, can you make an apple pie using only lemons? Calistoga Al

Promix often used, well used a lot it is a super popular mix. it has no pine. I would suggest making it just like 5-1-1 minus the 5. Look at the promix ingredients also.
You could also add some compost to help with drainage, and feed your plants. Compost also has the anti-fungal characteristics of pine, and considering you don't have any pine in the mix, I would add some. A small amount. A couple of handfuls per gallon. I like pine myself, and would use it.
It's anti-fungal properties alone are very helpful with peppers and tomatoes. It would be hard for me to believe you cannot find it. Many independent nurseries sell soil conditioner, which is pine. My guess is for some reason you don't want to use this top rate product.
I have used promix myself, but as a peat substitute in a 3-1-1 mix. That is the ratio I like to use myself.

FWIW - compost or other fine particles don't help with drainage unless all the other particles you're adding it to are smaller than the compost; and, compost is very low in actual nutrients - unless it's not finished, and then it ties up N and can produce a lot of heat as it finishes composting in the pot.

When we distill your request and reframe it as the challenge you face, I'd say you'll want to find some inorganic ingredients that are predominantly in the 1/8" size range and hold some water internally, then add a small volume of peat so you get enough water retention to satisfy you but not so much it fills up all the air spaces between the particles.

Like Al said, the more limited your options are, the more likely it is you'll encounter difficulty reaching your goals.

Al

Many composts are not fine, peat is fine, using peat yes will inhibit drainage, but the pine and perlite help. Peat is a compost. So I always found the message mixed, don't use compost, use compost...what? Composted pine works better than uncomposted. Composting is a great needed process in container culture.
Compost add bacteria which can help breakdown fertilizers like urea. Some plants can absorb urea directly, but some need Urease to break it down. Bacteria and fungi do that. Thus even soluble fertilizers can benefit from compost.
I disagree with the fine particle statement. Sand if fine but drains very well. Often used to increase drainage. Particle size does matter, but must be weighed with other considerations. Sand with clay is like concrete! So sand can stop drainage or increase it depending on other considerations. Compost can slow drainage or increase drainage depending on the situation. Not doubt in my example with peat, it will increase drainage. Why I suggested it to increase drainage in a mix without pine.
I guess we have to conclude that some of us here differ on how soil structure works.
I always add compost to my mixes and never had a drainage problem. The bad potting mixes are from too much peat. If you're worried about drainage worry about the peat content, not the other forms of compost. Compost also prevents root rot, that is very well documented. Many sell compost for pots touting the root rot prevention aspect. If it didn't drain well you would think that would not be possible.Giving advice that can lead to root rot should not be taken.
My career was spent as a scientist, so I like to use science as a basis for my gardening. Observation alone proves nothing. Here is one of thousands of studies showing the benefit of compost in containers.

Here is a link that might be useful: Rot rot in cucumbers

This post was edited by Drew51 on Fri, Jan 16, 15 at 8:01

Only finished composts are fine (small particle size) and present the issues I noted, which is why I added that qualifier - to let you know I'd considered the different stages of compost breakdown.

Flow through rates don't give a clear picture of how well soils drain (water retention). Sand might have a fairly rapid flow through rate, but it can also support tall perched water columns, which is the better measure of how well soils drain. Sand can increase drainage only if you're adding it to a mix of particles smaller than the sand particles; otherwise it does little more than clog macro pores and increase the ht of the PWT .

Composting isn't needed at ALL in container culture. You can grow perfectly healthy plants in a mixture of Turface and grit, pumice and grit, calcined DE and grit, or simply in a bucket of crushed glass if you really WANT to. I don't concern myself at all about a soil's ability to break down (compost) and "feed" the plant. I gladly shoulder that responsibility and concentrate on the soil's structure. The fertilizing part is monkey easy.

No one said you couldn't use compost and still make a good soil. Using compost and basing a soil on it are 2 different things, which brings us full circle to the thought that coarse compost isn't finished and as a result would have inherent issues. Finished compost will be fine, with little remaining but lignin, and as such would be fairly stable. Still, it's fine size at finish leaves us with a soil little different than a soil based entirely on peat.

Compost can't be said to prevent root rot. It might contain some bio-control agents that in some cases might help prevent some of the damping off issues, but the simple act of including compost in your container media doesn't ensure a growing experience free from fungal pathogens very often associated with soggy soil conditions, which we know are directly linked to particle size.

Thousands of growers come to GW annually with plant health issues directly related to water retention. The easiest and most efficient method of remedying the problem is by increasing the particle size of the growing media, and in doing so reduce or eliminate the limiting effects of perched water. Thousands and thousands of growers over the years can't all be wrong.

Al

Only finished composts are fine (small particle size) and present the issues I noted, which is why I added that qualifier - to let you know I'd considered the different stages of compost breakdown.

Flow through rates don't give a clear picture of how well soils drain (water retention). Sand might have a fairly rapid flow through rate, but it can also support tall perched water columns, which is the better measure of how well soils drain. Sand can increase drainage only if you're adding it to a mix of particles smaller than the sand particles; otherwise it does little more than clog macro pores and increase the ht of the PWT .

Composting isn't needed at ALL in container culture. You can grow perfectly healthy plants in a mixture of Turface and grit, pumice and grit, calcined DE and grit, or simply in a bucket of crushed glass if you really WANT to. I don't concern myself at all about a soil's ability to break down (compost) and "feed" the plant. I gladly shoulder that responsibility and concentrate on the soil's structure. The fertilizing part is monkey easy.

No one said you couldn't use compost and still make a good soil. Using compost and basing a soil on it are 2 different things, which brings us full circle to the thought that coarse compost isn't finished and as a result would have inherent issues. Finished compost will be fine, with little remaining but lignin, and as such would be fairly stable. Still, it's fine size at finish leaves us with a soil little different than a soil based entirely on peat.

Compost can't be said to prevent root rot. It might contain some bio-control agents that in some cases might help prevent some of the damping off issues, but the simple act of including compost in your container media doesn't ensure a growing experience free from fungal pathogens very often associated with soggy soil conditions, which we know are directly linked to particle size.

Thousands of growers come to GW annually with plant health issues directly related to water retention. The easiest and most efficient method of remedying the problem is by increasing the particle size of the growing media, and in doing so reduce or eliminate the limiting effects of perched water. Thousands and thousands of growers over the years can't all be wrong.

Al

Great answers but the OP might be OK with mixes that would hold way too much water for most.

It appears he is only growing annuals, or at least it seems so from the post. Maybe I"m assuming that from his user name. Is he only growing veggies?

Short growing season and extremely cold winters at 8000 feet in the Rocky Mountains will have their effects also.

He says the 10gal pots are fabric. If the 20 and 30 are also fabric then those tend to dry out quickly in low humidity and he is in a very low humidity area.

It's fine with me if someone is ok with a mix that holds a lot of water, but living in an arid clime offers no immunity from the effects of a soggy soil. The only saving grace would come from the fact that soggy soils won't remain soggy for quite as long in an arid climate.

Ideally, a grower would use a soil that isn't limiting because of excess water retention and water more frequently to compensate. Ideally for the plant, that is. We tend to mix our perspectives when we consider what someone's best course might be. For example, it might be in the plant's best interest if he used a soil that was fast (draining) and watered twice each day than if he used a soil that has a considerably tall PWT and holds enough water to last for a day or more. Each of us needs to decide what part convenience plays and what part maximizing the plant's ability to reach its potential plays in how much effort we're able or willing to expend.

I learned a long time ago not to judge someone who takes the convenience route. I consider supplying dependable info to be my job here - so the person deciding can base the decision on reliable info.

Al

Ideally, a grower would use a soil that isn't limiting because of excess water retention

What are the limitations of excess water?

I start my lettuce seedlings in 3 inch square pots in a tray full of water. The soil is saturated and the seeds seem to sprout better that way. I drain the water every other day. The roots come out the bottom of the pots right into the water and seem healthy to me. Then I transplant to large containers. I detect no odor so I don't think there is any anaerobic decay and the roots look healthy to me.

I design my container mix to hold a lot of water. Mostly peat, compost, bark and natural DE. I don't recommend calcined DE because it is hazardous to one's health. I water a lot and presume there is a PWT. In the summer I place some of the smaller containers (10 gal and less) in saucers. The more water the better the lettuce.

When I dig out the roots for the next batch they seem white and healthy to me. I detect no odor so it seems the excess water is doing no harm. Lots of water seems to be a benefit.

"What are the limitations of excess water?

The process of taking up water and the nutrients dissolved in water is energy driven. To burn the carbohydrates that drive root metabolism requires oxygen. When soil pore spaces are filled with water, they can't get the O2 they need, so water and nutrient uptake is limited.

Additionally, the very fine roots that do the lion's share of the plant's work die very quickly when deprived of O2. When air returns to the root zone, the plant must use energy reserves or a fraction of current energy production to regenerate the roots lost to the anaerobic soil conditions. This might not be immediately visible to the grower because the loss is often made manifest in lost potential, and lost potential in plants is something that can't ever be regained. Once lost, it's gone forever.

Al

I'm on the 'other side of the pass' from the San Luis Valley, to the west, and very familiar with your climate and ingredient issues. I grow all my peppers and eggplant in containers, with a fleet of 50-odd.

A few years ago, I stumbled on making my own mix using large quantities of bark off the beetle killed conifers - of which there is plenty to be had our part of the world.

I get mine by stripping the bark off firewood that was delivered, I have neighbors who drive up to stands of beetle-killed wood (pinion, ponderosa, spruce, whatever) with trash bags and a chisel, strip the bark off the dead trees - the best stuff is found on downed trees where the fungus and bugs have started to decompose the material.

Break it up with your hands and fill the trash bags. So its pieces anywhere from 1 inch cube to the size of your hand.

Then mixed that up with perlite - I buy 7 cubic foot bags at a nursery, - then I guess its your choice, peat, or bags of potting soil. Then a shovel or two of good old Colorado dirt, (our alkali soil buffers with the acidic pine bark) some Azomite for trace minerals, mix it all up, and voila.

With your cloth grow bags, they act like a wick, so moisture retention is an issue. Those larger pieces of bark will help considerably.

At the link is a thread about this on the rocky mt gardening forum, which might be of help.

Here is a link that might be useful: link to thread on using beetle kill pine bark in containers

MG Organic Garden Soil: (suggestion).

I checked a broken bag (@HD) last year, it had a 5-1-1 like structure. I could see a lot of pine bark in it.
So I would try that and add perlite to it. I think it was less expensive that stuff like potting mix and Pro Mix.

Seysonn