The best source for info on container mix recipes is the Container Gardening forum here as that is their focus - as opposed to folks who do in-ground gardening. That said, there are literally hundreds of discussions all over the forums here on 'best container mix', 'best potting mix', 'make your own recipes' for container mixes, etc. that the search will pull up for you. Many of them address specific plant's needs as no one mix works for all. Many cover the pH issues, water retention/drainage issues, compaction issues, nutrient supply/retention issues, mix sustainability issues (use and reuse), etc. so lots of good information is already available. Common points reconfirmed by all the discussions is that (1) container gardening is unique, a different world that shares little in common with in-ground gardening, 2) that the use of "dirt"/garden soil in a container is not recommended for several reasons, that (3) there is a big difference between "potting mixes" and "potting soils", and that (4) there are many high quality bagged potting mixes available depending on local availability. Probably the one container mix that gets the most discussion on the various forums is the 5-1-1- mix recipe discussed in great detail over on the Container gardening forum. Dave Here is a link that might be useful: Container Gardening forum

I would start in a very fast soil in 1 or 2 flat bottom flats or several half-flats (easier to handle when full of moist soil) w/o holes & tilt the flat so that gravity directs the water to 1 drain hole in the corner (or 2, if you like). Better yet, buy extra flats (really inexpensive) and nest them so the bottom is the collection tray/saucer. Set the top one on top of supports you'll leave in the bottom to keep the soil out of the effluent. A dome would prolly be helpful, too. Copy paste to browser for flats: http://homeharvest.com/propagationflatsdomesinserts.htm They (the plants) are no problem at all to lift from the flat & repot as they gain some size after germinating. Again, a fast soil in a 3.5 - 4.5" pot is about right. ($.19 -.27 - for pots) Copy/paste to browser: http://homeharvest.com/containergardenpotsplastic.htm I bought a package of 10 seeds this past summer. I started them outdoors in full sun, in a very shallow terra cotta saucer with the gritty mix in it. I scattered the seeds on top of the soil, then covered them with Turface fines, and misted the saucer twice daily to keep things moist. I got 6 plants from the 10 seeds. I'm guessing that's a pretty good %. I fertilized with the FP 9-3-6. I kept 2 plants with short internodes & gave the rest away. One has a stem caliper of about 1.25 inch and the other about 1", so they have grown very well. Also, I've done some pruning on them to shape them to my purposes, so the trunk caliper could have been greater with the additional energy input from the foliage I pruned. Al

Surely in the vastness that is Los Angeles County there must be at least one houseplant nursery that sells soil expressly aimed at owners of these plants. Have you tried finding recipes for such soil in garden books and maybe making your own. If you have such large quantity of plants that you need to buy such in bulk, then it would pay you to find a recipe for what plants you have. Remember, some plants require special attention to what's in their soil. For the most part though, commercial potting mixes is the most efficient and I might add...safest way to go. It can provide a formulation that house plants prefer in that it provides all the nutrients they need for a specific time. Here is one recipe you might consider: blend equal amounts of coarse sand, loam or good garden topsoil and peat moss, leaf mold or fir bark. To each 2 quarts of this mix, add 1/2 cup each charcoal and perlite. Each of these ingredients has a purpose. The topsoil contains particles of clay that holds fertilizer and makes it availablefor plant roots. Sand, perlite and leaf mold hold air around the roots which is essential for good plant growth. Leaf mold also provides nutrients. Charcoal bits keep the soil 'sweet'. Peat moss gives good structure to the soil and holds moisture. Any soil you make yourself must be sterilized. The loam or topsoil may contain pests and/or disease and weed seeds. Sterilizing takes care of this. To sterilize soil: thoroughly dampen the mix with water. Spread it out no more than 4 inches deep in shallow ovenproof pans. Place in a 180ºF oven and bake for at least 2 hours. Prepare to have your kitchen stink. An alternate method is to cover the pan with kitchen foil or clear baking wrap and seal. Insert a cooking thermometer through the centre of of the covering into the soil....but not touching the pan. Place in oven and heat until the soil temperature reaches 180º. Keep the temperature at that reading--no higher--for 30 minutes. Remove from oven and let it air for a few days. Store in paper or plastic bags.

I spend a lot of time at the Container Forum, just happened to wander over here! I recommend you post on the Container forum and talk to Al (Tapla) and JAG (Justaguy). The first mix will definitely be frowned on, the second mix is preferable if those are your only choices...with 50% fines it may retain water longer than optimal but that depends on your particular microclimate. Ideally you should need to water every day, means the mix is well drained with good gas exchange and fresh oxygen to the roots daily, think of container gardening as a cross between hydroponics and aeroponics...if you find yourself only needing to water every 2-3 days due to moisture retention then you won't have an optimal root environment and best results possible. Good luck. Tom