The potting mix I use is one I make myself. I start with black soil from a gardening outlet. I pick a cheap one, that hasn't been premixed, that is mainly soil such as a soil additive that has proably been made from leaf compost. The type that is used outdoors typically. With this I mix about 1/4 fine peat moss and 1/4 perlite.
Sometimes I use soil straight from the garden. with this I add about 1/3 of cattle compost as my soil is sandy and then peat moss and perlite.
The soil is placed in the planting trays. I use the flats with 10 individual trays in them. The trays are filled about 3/4 full and then soil is lightly tramped down. The end of a piece of 2x4 is great for this. Then I scatter seeds around, as evenly as possible. Add 1/2 " of soil and again lightly tramp down.
I have used pre mixes but have found that they are inconsistent and often will pack down too heavily. Peat moss and perlite provide for moisture retention and air space.
I don't place outside as rain can wash out seeds. If outside then top 1/2" proably should be course sand.
From: Bill Chaney <email@example.com>
To: firstname.lastname@example.org; email@example.com
Sent: Fri, Oct 9, 2009 1:25 am
Subject: [iris-photos] Potting medium for seedling pots
I would like some advice on the best potting medium for seedling pots. I have found most of the commercial potting soils hold too much water and have too little pore space. Any suggestions? Mix with sand? Or vermiculite? And what about the soil for the top? The same, or something more course?
Any suggestions would be welcome.