I'd appreciate any tips! Despite gardening for most of my life, I've always done direct-sowing and never started indoors. New adventures!
Be sure to use soil free seed starting mix, especially for your tomatoes. It totally sucks to lose all your babies to a soil born fungus (speaking from experience).
When you pot up, if you choose to use a soil based medium, then top the soil with vermiculite or perlite to keep the soil from splashing up on the stems and leaves of your babies. By the time you hit your final pot up or plant-out, they should be rugged enough to repel soil-born fungus and pathogens, but as I'm sure you know, a good mulch is still a good idea.
Don't jump the gun and start things too early - you'll end up with leggy wimpy plants. (again, experience)
Don't worry if your tomatoes are leggy - they will send out adventitious roots, so just pinch off the lower leaves and pot them deeper every time you pot up. When you put them out in the garden, pinch off the bottom leaves and suckers and sink them down deep. This will give you robust plants that take right off.
I vaguely recall reading that onions don't transplant well. You might be better off planting the seeds in a planter and just moving the planter outside at the right time.
Marigolds are a great thing to seed start. I use them abundantly in my gardens, and they are so easy to grow. I hate it when I have to spend $20 for a flat of them when I could have grown 3x as many for half as much!
Oh! another thought - if you line the inside of your green house wiht aluminum foil, it will help bounce the light around. No sense letting that light escape out of the plastic and go to waste. Maybe just wrap the foil around the top bar and let the roll fall to the floor? I don't know what your set up looks like, but might be worth a try.
Good luck and fun wishes!
Tahai
*edited for spelling errors 1/11/24*