You can use potting soil to start seeds, but you will face more problems than with proper seed starting mix. Potting soil is chunky and holds too much water for your tiny seeds. These traits create trouble for seeds trying to sprout and grow their first roots in your trays at home.
I tested both mixes side by side last spring with tomato seeds to see the real difference. The seed starting mix vs potting soil results surprised me a lot. Seeds in the potting soil took three extra days to sprout in my setup. Many came up crooked because they had to push around large bark chunks in the mix.
In my experience, potting soil causes the most trouble with moisture levels in your trays. The mix stays wet for days instead of drying to your ideal moist level for seedlings. This soggy soil leads to damping off disease that kills your seedlings at the soil line within hours once it starts spreading through your tray.
My neighbor tried potting soil for her pepper starts last year because it cost less at her local store. Half her seeds never came up at all from those trays she planted. The ones that did grew weak and yellow within two weeks of sprouting. She switched to proper mix and her success rate jumped to 90% with the same seed packet.
The best soil for seed starting feels fine and uniform with no large chunks you can see or feel. UMD Extension says to use sterile mixes with a pH of 6.0 to 6.5 that hold moisture like a wrung-out sponge. Potting soils often contain bark, fertilizer pellets, and bits that block your tiny roots from growing straight down.
If potting soil is all you have on hand right now, you can make it work better with one simple fix though. Mix it 50/50 with perlite or vermiculite to improve your drainage and reduce moisture problems. This blend drains faster and gives your roots more air pockets to breathe while they grow down into your cells.
Spend a few extra dollars on proper seed starting mix if you can find it at your local garden center nearby. A small bag costs around $5 to $8 and starts hundreds of your seeds with much higher success rates overall. Your seedlings will grow stronger and healthier from day one with the right growing medium under them.
Read the full article: When to Start Seeds Indoors: Ultimate Guide
