Perhaps my pumice source ('Dry-stall' from the feed store) is the culprit
as that is new this year .... or .... the rain water collected from the
roof that I use for irrigation?
Your problem is that the top surface is not drying out because the
Dry-stall absorbs so much moisture. Topdress with something like granite
grit. Rainwater is probably the source of the moss.
Moss in seedling pots is not always detrimental... Trillium and Paris love
it.
Mark Mazer
Hertford, North Carolina USA
USDA 8a