I will be starting my tomatoes this week Wednesday from seed. I am in S.E. WI. I normally start the seeds in a small container. Once they germinate, I put them under my 48" florescent lights in my basement. When the seedlings get their first true leaf then I transplant them to individual pots. I use the plastic cells sold in a sheet (18 cells per sheet). Yes I do fertilize with a liquid fertilizer. Normally I mix the fertilizer at 1/2 strength and water the tomatoes. Normally I fertilize 2-3 times during the 6-8 weeks that I have them in these pots before putting them outside and hardening them off for a week before planting in the garden.

Correct potting mix? That is a tough question. I have purchased numerous different brands over the years and find many that I do not like. Some are very fine and do not seem to dry out very quickly. Some have worked well. Since I am at the mercy of what I can find at the chain stores near me I have to purchase and hope for the best. I just picked up another bag of starter mix yesterday. I found Miracle Grow brand, Jiffy brand and one other brand.

I miss the good old days when I worked at a greenhouse and we used to sterilize our own soil and make our own mix with peat and vermiculite. The best I can find today would be a Fafard mix but it was sold in a very large volume. Since I only have been starting just tomatoes the past few years, I did not want to purchase and store such a large bag for future use.

@spartanapples,

Thanks for replying

When you say "When the seedlings get their first true leaf" do you mean when the true leaf is 1/2" long as I stated or sooner?

When you say plastic pot sheets, do you mean 3" ones like this?

http://www.greenhousemegastore.com/product/12791/thermoformed-plastic-seed-pots?gclid=Cj0KCQjwnqzWBRC_ARIsABSMVTN_nYHByFiHeSEA_5NBIdsUyOOgPiVG0fDcLb3XbeAewbFQ36GS01kaAnW-EALw_wcB

If so, do you keep them in those until transplanting out or do you repot again?

The 1801 cell sheets I use look similar to your attachment above. I transplant into them and leave them in those cells until I plant out in my garden late May.

I like to transplant as soon as possible once the tomatoes get their first true leaf. The faster they are taken out of the starter flat and transplanted the better they are as they are then spaced out. I like my tomato plants to be short, bushy and thick stems when I put them in my garden. As soon as the true leaf is big enough I transplant. I guess 1/2" long sounds right as I have never actually measured them before transplanting out of the seed flat.

Tomatoes are resilient. Unless you're rough and breaking roots, when exactly you pot up isn't going to make or break your season.

As for potting medium, etc. it doesn't make a huge difference. I've used seed starter, I've used Miracle Gro given to me by a relative who had no use for a big bag of it, etc. As long as it's not soil but a mix for indoor/container plants, it should work. The big issue with non-seed-starter mixes is that they might have fungus gnats in them, which can wreak havoc on your seedlings by eating their roots and carrying pathogens that cause damping off and become a real annoyance in the home. I always have water with mosquito bits or mosquito dunks soaking in them to use to water all my indoor plants, and I have no fungus gnat problems and haven't had anything at all damp off since. Not even notorious seedlings like basil.

Re: fertilizer--if they look like they need it, I fertilize. If not, I don't. I find that I don't really need to if I use something like Miracle Gro. If I use sterile seed starter, I usually end up fertilizing lightly when I pot up with a dilute water soluble fert.

I start off my seeds in 1.5" x 1.5 "x 2" cells, then when they're about at the point where the second set of true leaves is starting to come in, I pot them up into SOLO cups and, weather permitting, start to harden them off. They grow really quickly during the hardening off process so that they're a totally decent size when I finally plant them out. Sometimes, if things in the garden aren't on schedule, they live outdoors in the SOLO cups for a little longer.

But that's when things are going according to plan. When they're not, I've planted out 2" plants with one true leaf and I've planted out plants pushing a foot and a half, and they've all done fine. Tomatoes may be prima donnas when it comes to disease, but they're tough little plants otherwise and fairly forgiving.

Seed leaves are the first leaves on a plant. The next leaves that come out are true leaves. They say you should wait for the first true leaves before transplanting tomatoes but I have transplanted them with only the seed leaves and they've done well. When I transplant I use a deep pot--I use the large size of yogurt containers with holes that I've put in the bottom. I used to use SOLO cups but switched to the yogurt containers because they hold more soil and gives the roots more room to grow. I guess what you use depends on how soon you can set them out and how large your plants will be by then. I sink the seedling up to the leaves in the soil. Tomatoes unlike some other plants will grow roots all along that stem. It does cut down on top growth a bit at first but they soon catch up and they have an excellent root system for planting out.