Arlene - for just starting seeds for transplant out, honestly, any halfway decent commercial soilless potting mix will do. I tend to avoid the ones that contain coir just because I feel the jury is still out on the safety/efficacy of unknown sources of coir; but that said, I accidentally bought some Miracle Gro Moisture Control mix this past spring and it doesn't seem to have killed anything so far, LOL! The MG Moisture Control has coir in it; the "regular" MG does not. When I used to mix my own, it was 1:1 or 2:1 peat and coarse vermiculite but I haven't been able to lay hands on coarse vermiculite for ages. Apparently, it turns out, the major mining operation/producer of vermiculite shut down in the 90s (I gather there was some scandal involved, over safety or what, I don't know) and since then sources of vermiculite are much fewer and farther between. Then I was using 1:1 peat and a good garden soil (MG was my choice) - which is OK for seed starting but no great shakes for anything likely to be in a pot for more than a single growing season. Now I am experimenting with various peat and "other stuff" mixes, including some barks that have been deemed unsuitable for long term mixes (too many fines, etc). For longer term I will be trying peat/pumice and peat/pumice/bark blends but haven't got started on that yet. Today I will be planting some ginger in a 1:1:1 peat/pumice/soil conditioner blend. My seed starting mix for the coming season will be: 1:1 peat and fines sifted from pine bark OR 1:1 peat and Scotts Turf Builder - a very consistent but very small pine bark product, with a small component of compost and "forest products" plus a very very small amount of fertilizer (1:1:1) I will alternate rows in my paks with one or the other, with the same plants planted in one row of each. I will have lots of extra starts to share, I think, LOL! I have actually started seeds in 100% peat. While there are undoubtedly seeds that won't start well in that, nothing I grew that year turned a hair. Seeds are generally pretty darn forgiving. I don't think you have a lot to worry about, whatever you choose. I would suggest choosing the option that is most economical for you, whether that is watching for sales of MG or Hyponex or what have you, or going with a mix of your own.

Expendable, if you are require large amounts for nursery use, you may want to contact a Fafard representative. They can deal in bulk deliveries of most of their whole sale line of products. I've been using their Heavy Weight mixes (see attached link) for many years...both when I was growing as a professional and now that I just require tiny amounts, I have a local garden center special order it for me. It's the only potting mix that I recommend EVER. If you look at the attached link, you'll see that these nursery quality mixes can be purchased in 55 cu.yd. bags. They also sell tractor trailer loads of a mix (which I have never seen). That's my suggestion, not knowing what your use of the product will be. If you are growing in containers, you'll want something very coarse textured. Your crop determines if the m ix should be more peaty or more barky. Here is a link that might be useful: Check this out

The manager at my local retail nursery told me something interesting when I asked him if he could get Fertilome UPM. I told him some friends in New Mexico highly recommended it and that I was interested in giving it a try. He told me that the UPM I would get way over here in Mississippi wouldn't be the same. He said that Fertilome would be contracting out the production of UPM to a different company closer to where I am located and that it would likely not be the same mix as that my friends in New Mexico would buy out there. I found that interesting. I wonder if it is true.

I'm sorry jtcm but it wasn't my intent to offer that link as some sort of definitive authority, just a source of additional info on the question. There are multiple other sources available online that you can Google if interested. I just thought you were looking for general info. While we're at it...let's re-use our trays without cleaning them and keep the seedlings covered until the true leaves emerge. I don't see how that follows. There is a great deal of difference between adding small amounts of well-cooked compost to a mix and intentionally using dirty trays/containers or keeping seedlings covered. As I said above, I'm far from the only person who uses compost in their seed starting mix. A search here will pull up many discussions about it. And if you believe your seed starting mix is actually "sterile", in the usual sense of the word, then you are misled. Most all packaged seed starting mixes, including ProMix and Metro Mix not to mention all the Scotts products add composted ingredients in various forms to their mix. All the organic seed germination mixes on the market include compost in some form. ProMix even advertises the addition of mycorrhizal fungi to their mix as one of their selling points. And then those bags get transported all packed together inside a hot truck to the Home Depot or Lowe's or Walmart outside store yard to lay around in the sun and the rain until someone buys them. Meanwhile the composting process started in the factory by mixing those ingredients goes on in the bag. Feel free to do some additional research on the issue yourself if interested or, if you prefer, just don't use it. The seeds will germinate either way. ;) Dave