What size for potting tomato seedlings?

[brooksms]

As a first time gardener, I went against all recommendations and started tomato seeds too early! It began as an experiment to see if I could grow tomato transplants from seed using what I already had at home. If they were successful, I would know better than to buy extra seed starting materials when the time comes. For me, that time was going to be Feb. 28th as our last frost is between March 30th & April 30th in zone 7. So, I'm about five weeks too early. Lo and behold, they are under a lamp and growing quickly! I want to see if they can make it until I'm able move them to raised beds outside, just to continue the experiment. They are in solo cups at the moment and I only want to pot up once before mid April. What size pot should I get? I'm just not sure how large they get in that amount of time. Or, are they doomed for failure and I should start over in four weeks?

[applestar]

It would help if you can move them to a cooler location -- 55-65°F and use very bright lights. What are you using right now? While growing inside, lower than optimum lights will make them stretch for the lights -- taller and weaker than you want.

Don't feed with too much fertilizer and let the top surface of the soil mix feel dry (nothing sticks to your dry finger) before watering.

What size solo cups are they in right now?

[brooksms]

The bulb I'm using is 1400 lumens (set 1-2 inches from the seedlings) for now and they're by a south facing window. I was thinking of buying a 4ft long shop light with t8 bulbs to use when I put them in pots. They are in 18oz cups right now.

[applestar]

Last year, my tomato plants that were the last to be planted out were growing 2 to a 1/2 gal long container -- that would be basically 1 quart each or 32 oz and twice what yours are in now.

You can see some photos here. You'll see I'm planting them 3 per container at first, and then later on, I separated them to 2 per.
Subject: Finally! Off to a haphazard start for the 2014 season

[brooksms]

Thank you! It is hard for me to imagine how much growth will happen in 12 weeks.