Pablo, post your request on the Containers forum or review their archives. Al (tapla) - a regular poster there - is considered an expert on container soils, drainage, etc., and there has been lots of discussion on homemade mixes. As you know, growing in containers is a good bit different than growing in the ground and different "rules" and techniques apply.

I have a compost pile out back. This is special stuff. I can plant a trowel on evening and the next morning, I'll have a shovel.

My grandfather was a lazy farmer. Every day, when it was time for him to clean the barn, it was also lunchtime. So he'd take the tractor out back, park it in the same area, and start the spreader. He'd do this every day, for enough years he created three piles, each about the size of a basketball court, and six feet deep.

That was thirty years ago. Since then, I feed bales to my cows near these piles through the winter. The traffic grinds the top few inches into a powder that's so fine it's only slightly more coarse than powdered graphite.

I'll scoop about two yards of this stuff into a trailer (takes about twenty minutes with a flat bottomed shovel) and mix it 50/50 with vermiculite, then mix that 1:3 with perlite.

That's my basic personal house plant/seed starter mix. To that I will add various other components according to what plants I'm dealing with (rice hulls for orchids, sand for succulents, more perlite if I'm rooting cuttings, etc.).

The only problem I have with this mix...is it's light. It drains water like you wouldn't believe. Conversely, for a seed mix, it's great. I have almost no problems with damping off or anything else because it drains so quickly.

I'll second gardengal's suggestion on Al's Recipe, and even provide links to 2 long Container Forum threads on it.

They can be found here and here.

It's fascinating reading, and is full of valuable information on a condition which exists in all plant containers, known as Perched Water Table (PWT).

I disagree....using anything but what is best for starting seedlings, and plants, is unnecessary and dangerous....for the plants.

Fresh potting soil is all that is needed.

Household compost is an unknown factor....how good is it...and it may be, like manure, too hot for starting such tender roots.
Whether yu have had good results is a quetionable testiment.
What else can one say when they've convinced themselves that their compost is a world beater.

Fresh potting soil is....and always will be...what should be used.

Good grief, Jeannie! ;-)

A great many people don't use potting medium, jeannie. I'll typically use pure perlite! Or a mixture of my potting mix (which is bark based) and perlite. Or Turface. Or all sand.

The materials that you're wondering about, Pablo, are wonderful when used in situ, but not in containers (typically). Containerized soil is held captive and needs to be constructed in an entirely different way. Please take the time to read the links that Donn attached for you.

For years before the current glut of "potting" mixes were readily available people regularly made their own, most often with the soil from their garden and compost. The one thing you want to be sure of is that what you use drains well so most people with clay soil would find some sand someplace and mix that with their compost, although a clay soil well endowed with organic matter will drain okay.
Many of the older books I have (pre 1960) talk about potting mixes consisting of a 50/50 mixture of compost and garden soil and no mention of soil borne diseases. Most of the books that are post 1960 talk about the necessity of "sterilizing" these potting soil mixes because of plant disease. Something we have done since the 1950's has caused an increase in the potential for soil borne plant diseases.

Jeannie does have a point. Without the proper testing equipment and high quality ingredients homemade potting mix is a risk. But it may be an acceptable one for many people, and I do find it satisfying. Usually works very well with just some extra weed seeds. The results do vary a little from batch to batch. What Jeannie does not point out is how difficult it is to purchase a really high quality organic potting mix. Or even non-organic. I know of only two in this area and you need to seek them out. They are Vermont Compost Company and McEnro (sp?) Organics out of NY State. The VCC mix is a little more expensive but the consensus seems to be that it is the very best. All of the widely available commercial ones, even Pro-Mix, pale by comparison. All of these are peat based. In the Northeast peat is an affordable option and the rate of harvest is considered by most to be sustainable. Not trying to restart the peat debate... Maybe pure leaf mold would be a good substitute for peat? Might tie up a little nitrogen so require a little extra blood meal or other nitrogen source in the mix or added later?

David B.

I think we have all experienced the situation of what was in gardening is no longer considered to be the best method. Knowledge, experience and scientific evidence have all progressed over the years as has the incredible popularity of gardening and methods, techniques and recommendations change. Container gardening in particular is on a huge upswing - the most rapidly growing aspect of home horticulture. That combined with the studies done with regards to commercial container growing operations have produced the "glut" of potting mediums. Lightweight, porous and very free draining media has been found to produce the best results. That can be reproduced at home but it is best done with some study beforehand to understand the limitations that certain, at hand home materials will create.

I usually use a store bought seed starting mix, but this year I decided to try a homemade mix for seed starting. We used some well-aged homemade compost. It was finely sifted and placed in a covered container in September. We then mixed 4 parts of this screened and sifted compost with 2 parts peat moss, 1 part perlite, and 1 part vermiculite. So far our plants look really healthy. Cabbage, basil, sage, and dill are all doing fine in this mix. No signs of mold, rot, damping off, or bugs yet. I guess this is the year for experimenting, because I have also purchased one of those fancy seed starter kits from Gurney's. It was a total impulse buy. I have started some more cabbage, broccoli, tomatoes, peppers, and spinach in that. I sowed these seeds 2 days ago and several have already sprouted. Germination seems like it will not be a problem with this kit. I am more worried about the roots and how well they will grow in the provided "grow plugs". Also, because the styrofoam tray that the plugs sit in is constantly floating on water, it seems like the plants might not like being constantly saturated as they are growing. I am going to keep an eye on them and if I see any signs that they are not doing well, I will take them out of this tray and put them in their own pots. So far though everything is looking good. I will keep you updated on the progress of my little friends!

A fella over on youtube uses straight vermiculite to start his seeds.

You'll need to get some nutrients to the seedlings before they got too big, though.

I also hear that a small fan blowing on the seedlings is supposed to cut down on some of the diseases (and make the plants a lil sturdier).

Might I ask why the desire to make you own starter mix rather than go with a high quality store bought mix?

heptacodium,

Then just dont use the vermiculite and only use the manure and peat. I did with great results.

This post was edited by TheMasterGardener1 on Sat, Jan 19, 13 at 16:41