There are as many different ideas about starting tomatoes as there are tomato gardeners. So what I have to say is opinion laced with some experience and wishful thinking; what I say and what I end up doing are often at odds.
Seed starting (or more accurately, refraining from it) is one of the more difficult areas for me. Winter never seems to end, and that itch to get seeding is powerful. I settled on a compromise; I allow myself two plants to gamble with, started in flats under lights a couple of weeks before the main crop seedlings are started. They go out into garden before they should, under a double layer of protection.
It seems like the seed packets might be right. Go figure. Trying to get a jump on things by planting extra early really won’t do you any favors. I believe the younger, smaller seedlings catch up to the larger earlier ones quickly, and then outperform them. So with much effort, I restrain myself from starting seeds more than 6 weeks before they’re to be moved outside, and 4 weeks is my new goal. It’ll probably end up being 5.
I always plant double the number of seeds that’ll be used. Insurance against clumsy hands and bad luck. They’re planted in flats with the 9-pack inserts. When the seedlings get their first true leaves, they’re transplanted deep, right up to the leaves, in 4 inch pots with a nice organic potting mix (a little worm castings go a long way).
To keep the little fellas happy, the grow lights stay really close; I hang them 1″-2″ above the leaves for 14-16 hours a day using a timer. They’re just plain old shop lights with plain old fluorescent bulbs.
If you want big thick stems (and you do) running a small fan in your growing area for a few hours a day really does seem to help, as does deep transplanting.
Then, when the seedlings start to look like their legs are outgrowing their bodies again, they get another up-potting, this time to cut-off 1/2 gallon milk cartons filled with homemade potting mix, which I can’t describe because it’s never the same twice. It does involve worm castings at some point, and that’s enough for me. They get buried deep again, since tomato plants form roots from buried stem.
And finally they see daylight for hardening off. A whole nutther adventure.
This is how I start tomatoes. If anyone believes any of it’s is pure rot, absolutely say so. Or if you have secret tips for a poor, winter-socked gardener, by all means let ’em rip. I’m here to learn.