Thanks, Sue! Now I recall it being called something like "Innes Compost #9".
I'm glad to hear that it is one word used as a name for two different kinds of things. I've always heard that "seed-starting stuff" should be as nearly sterile as possible, but also read that Brits started seeds in "compost", which I always thought of as "compost-heap-compost", the least sterile thing imaginable.
But now that I've looked it up, I have a NEW concern to keep me awake nights. The Innes "compost" mixes for seed-starting, rooting cuttings, pricking out, potting up and container plants are all based on LOAM! Also very far from sterile!
...
OK, now I see: "sterilized loam". Now I can sleep again.
"Loam plus peat and sand". I wonder what they'll switch to as peat becomes more expensive, and then unavailable?
