oh, i forgot. my fall/winter garden will include a variety of heirloom carrots, beets, radishes, brassicas, salad greens, favas, and creole garlic, as well as common herbs, if that is in any way helpful to know in determining the best mix composition.

thank you all again...i am ALWAYS eager to learn from the BEST!

I have tomatoes in a 3-1-1 and 5-1-1 (bark-peat-perlite) mix in earthtainers and earth boxes. 2 Tomatoes per box and they are over 10 feet tall at this point. So far those mixes are still wicking fast enough to support the tomatoes.

I guess I'm saying I don't think you will have a problem no matter how you combine your ingredients. What you have will hold and wick more water than the mixes I use which are working with tomatoes in 100 degree heat. I might reduce the perlite proportion but that's me..

I find vermiculite to be very fragile in a mix. Even if it's sifted beforehand, the weight of the mix around it and the force of the mixing is enough to break it into much smaller pieces, which will make it act in a different way than expected, right off the bat. All my mixes with vermiculite ended up completely anaerobic, and I've stopped using it entirely.

I'd say if you wanted to use less vermiculite you could probably replace it with more bark fines. Also, both bark and peat repel water if they completely dry out, so I'd start with wet or damp materials, and keep an eye on it to make sure it doesn't get too dry.

Good luck, have fun, keep notes, report back! :) Also, take pictures once you get some seedlings!

ah. thank you for the advice. so, pixel pepper, when vermiculite is weighed down by the surrounding mix, it inhibits the penetration of oxygen through the media? i am wondering if i can get away with leaving it out of my recipe. it cost $30 for 4 cubic feet, and if it's not going to do much good anyway, then i'd be best returning it to the store before i tear the bag open. it is by far the priciest ingredient in the mix.

redshirtcat, if i can get away with scrapping the vermiculite, i may try something like the 3-1-1 formula you use. if 3-1-1 works for you in missouri, then might it work for me in south texas?

pixel pepper, you say i can use bark fines instead of vermiculite, but i heard that bark fines are more for drainage than retention? or is that incorrect? anyway, it's not much of a concern in winter here, but i do want the mix to last for a few seasons (amending as necessary as the bark breaks down), and summers here are brutally hot (100+ degrees F) and often quite dry. i am planning on tomatoes for next summer, and i can only imagine how thirsty they will get.

i will have to remember to take some pictures, and i will certainly report back with them. here's hoping for a bountiful harvest!

As much as mix is important ,the size of the materials has the greatest impact . Thew largest portion should be pine bark less than 3/8 inch. Pine bark 50 % peat 30 % then 20 % Perlite . No worm castings at all

ah. dickie, the pieces are about a 1/4" in size, so i should be set there. but why no worm castings? i thought they were a good all-purpose soil additive? especially since i can't add heavier composts (holds too much moisture in a sub-irrigated system).

ydfz,

Vermiculite by itself doesn't inhibit aeration, but broken, very small pieces of vermiculite will create the dreaded perched water table. That goes along with what dickieficke says. Since the worm castings are also small particles(and break into smaller pieces over time), that will influence how long the mix has good aeration.

Bark is multi-purpose in a mix. It's much better for drainage than peat, and also holds water (maybe not as much as vermiculite or peat, but definitely more than perlite).

I think as long as the mix has good aeration and is durable enough to last for a while, the exact ratio of components doesn't matter so much. And don't worry if it doesn't work exactly the way you think it should the first time. It may take a couple of tries to find a mix that's good year-round in your climate.

UPDATE! i wanted to report back with some preliminary results if anyone is interested.

per everyone's advice, i ditched the vermiculite and went with a strictly bark-peat-perlite mix. last weekend, i whipped up 16.4 cu ft of mix, which filled 5 big sterilite tubs. it worked out to:

36.5% (6 cu ft, 3 bags) bark fines
36.5% (6 cu ft, 1 bale) peat moss (expanded)
27% (4.4 cu ft, 1 bag) coarse perlite

(plus 1 gallon of dolomite lime (1 cup/cu ft) for ph balance and 2 gallons (2 cups/cu ft) of espoma garden-tone fertilizer).

THIS RECIPE HAS ISSUES. BEWARE: after making the mix, wetting it down, filling the containers, sowing my seeds, and observing for a week, it seems the proportion of perlite is much too high. the mix is supremely light and virtually impossible to compact (i tried, it just stays super loose), and there is plenty of oxygen-containing airspace. i realize that these all sound like good things. HOWEVER, the soil is so fluffy from being full of perlite that it's not wicking water up all that well. the base of the containers are soupy bogs, while the top inch is bone dry. this has made starting seeds difficult because the seedlings are too tiny to reach the vast water reserves (this would not be a problem with larger transplants).

in the meantime, i am top-watering the seedlings until they are large enough to reach the moister mix a couple of inches down. next season, i will cut the mix with additional peat and bark to reduce the proportion of perlite.

i have much more bulk ingredients and more containers to fill this season, and so i am revising the above recipe by using only half of the 4.4 cu ft bag of perlite per batch, which puts me at

42% bark
42% peat
16% perlite

if the little veggie babies survive, i will report back with pictures of the setup. happy gardening!