Before going to farm school, I didn’t know the difference between soil for germinating seeds, soil for filling raised beds, compost or the dirt in my backyard. The assorted soil products seemed to me an elaborate marketing scheme. How wrong I was! Turns out, if you start your seeds in optimal soil conditions they’re going to make happier, more productive plants down the road. We’ve learned that (and most farmy things) the hard way so you don’t have to.
Michigan State University Extension explains the difference between potting soil and seed-starting mix. “Soilless seed-starting mixes have a finer texture and are made from ingredients such as milled peat moss, perlite, coconut coir fiber and vermiculite. Although potting soils may be used to start seeds, they tend to have a more-coarse texture and may contain field soil, compost or composted manure along with vermiculite, peat moss or perlite. Some seed-starting or potting mixes may contain fertilizer as an additive. Some products contain enough fertilizer to provide seedlings with sufficient nutrients to last up to three months, while others may have no added nutrients.”
Ask your trusted local nursery for what they recommend for seed starting or try your hand at making your own germination blend using this recipe from OSU Extension: https://extension.oregonstate.