For years I've used this combination: 1 part sphagnum peat, 1 part vermiculite, 1 part perlite. It's organic, you can get all the ingredients at Walmart, Lowe's or Home Depot, it's lightweight, and the sphagnum peat has anti bacterial qualities. It's great for starting seeds! To use to plant in containers, I add one part compost. As far as fertilizing goes, as seedlings develop I use light water-soluble fertilizer. For container plants, the compost does the trick for feeding. Hope this helps. There's more info on the link below (scroll down to mid-page).

Here is a link that might be useful: Potting mix to use when starting tomato seeds

Your requirements are apposing each other, yet you want ONE homemade mix? I would suggest a lot more study of container mixes, starting with information already posted on this forum. Al

For years and years I used a bagged potting soil, or thought I was doing my plants a favor by mixing the usual extras into bagged potting soils... and then I read the article linked below... and my entire outlook on container growing changed. I wish I had read the information included decades sooner! I wish I had known the basic science so much sooner!

I don't mind going a little bit out of my way to locate the ingredients for a medium mix that will allow my plants to grow optimally. It actually wasn't that difficult to locate what I need. I use it for everything, from seed starting to cacti, from bulbs to orchids, from trees to annuals and perennials. I grow everything in it.

I use a rendition of the basic recipe for Gritty Mix. I use fir bark, a coarse perlite, and crushed granite chips... all available rather locally. I'd prefer to use turface instead of the perlite, but I don't have any at the moment. It's on my list for spring shopping!

Organic items and methods are great for growing outdoors in garden beds, but do not necessarily make for healthy container plantings. It's actually better to go with a more inorganic medium and growing methods within the confines of containers.

Outdoors, Mother Nature uses an army of worms, nematodes, bacterias, fungi, and other microscopic critters to help decompose matter into usable food for plants, to aerate the soil, and to maintain a balance of good and bad, shall we say. This same army is not present within a container, and it's impossible to maintain the balances required. This is the simplified reason why inorganic is better for container growing.

What we want to do in a container is help maintain a good level of aeration, keep the medium from compacting quickly, and we want to maintain control of moisture and nutrition. With a more inorganic medium, we can do these things. Plants actually intake water in vapor form, and they require fresh oxygen at root level. With a grittier medium, these things are possible. The larger particles help to maintain those tiny air pockets, and because the items are mostly inorganic, they don't compact at a fast rate.

Actually, all the information necessary for growing great containerized plants is in the linked article.

Here is a link that might be useful: Container Soils - Water Movement & Retention 12

Small bark, perlite (all can be bought at HD)can be mixed in to bagged mixes. You can then add anything else you want to the mix, depending on how loose you want it.

For seeds, I've used plain seed-starting mixes without any problems. For damping off and other fungal problems, you have to make sure the seedlings get good air circulation. I use a small fan to blow on the trays. Once the seeds germinate, I take the covers off or raise them to allow air flow.

If you want organic, you would use fish emulsion or other organic fertilizers. I use regular Miracle Gro or whatever I have handy.

I treat my outdoor containers differently than indoor. Outdoor are mostly annuals and I only deal with the top 1/3rd of the containers. The rest of the containers are just fillers. Plain potting mix with perlite is fine for the annuals.

Jane

Adding larger chunks of anything to the finer, siltier potting soils doesn't really affect it in a positive way. The finer particles fill in around the larger ones, negating the air pockets you're trying to create. That's the whole idea behind the additions.

Imagine a bowl of pudding... adding raisins to the pudding doesn't create air pockets... the pudding settles around the raisins and any air pockets you try to create are gone. This is exactly what happens to the finer, smaller particled, siltier soils.

In order to maintain the needed air pockets, and to keep a soil from compacting, it helps to begin with grittier, larger particled soil ingredients.

Miracle Gro liquid is a decent fertilizer. Most of the growers I know use Foliage Pro, and the results are excellent. It contains all the nutrients and micro-nutrients plants require. I would avoid organic fertilizers in containers, however... they typically do not break down into usable food for your plants.

I water thoroughly using a weak solution of Miracle Gro about 3 out of 4 times watering. On the 4th watering, I flush the pots with clear water to remove any accumulated salts and minerals. Leaching container plants is an important process, and necessary to the continued health of the plants.

I'm with the other Al - I don't think there is a single mix that could possibly incorporate everything you list as requirements. It's kind of like saying "I want a car that will go from 0-60 mph in four seconds, and I want it to get 80 mpg, and I want to drive from NY to LA in 1 day w/o breaking any speed limits".

Al's suggestion to make yourself more familiar with how container soils actually work, and Jodi's suggestions, were all good ones.

Al

Jane wrote: "Small bark, perlite (all can be bought at HD)can be mixed in to bagged mixes. "

I recommend small bark and perlite. Works well for me.

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Jane

With the exception of the fertilization, you can easily build a perfectly acceptable potting mix any number of ways. And with a little bit of 'that' or a lesser amount of 'this', you can adapt a decent mix to specific needs.

I would also suggest that you keep notes of the ingredients and their amounts,
so that you can reproduce the mix for next year's growing.

Josh