I've been using a commercial starting medium (Promix) for starting seeds for years, with good results.
This year, ran out of fresh stock so started the seeds in some of last year's growing-on mix - half soil, half Promix, Mar 10 - 14.
Spotty germination resulted; I figured I wasn't paying enough attention, and so seeded another pot of my staple NB11 Mar 31, this time in Promix.
The result - a pot full of seedlings, like previous years. No difference in light, temp, seeding rate and procedure, or water management.
The cup on the left is the Mar 31 sowing.
This year, ran out of fresh stock so started the seeds in some of last year's growing-on mix - half soil, half Promix, Mar 10 - 14.
Spotty germination resulted; I figured I wasn't paying enough attention, and so seeded another pot of my staple NB11 Mar 31, this time in Promix.
The result - a pot full of seedlings, like previous years. No difference in light, temp, seeding rate and procedure, or water management.
The cup on the left is the Mar 31 sowing.