I would wait another week and any time you can get them outside in 50+F, dappled sun and a light breeze for an hr. or so I would.

wait for alittle while.

Here is a link that might be useful: GrowingHeirloomTomatoes

Is there something I should be looking for so I know when to re-pot again? Signs that they are getting root bound. Such as needing daily watering or even more often. Since you went up to 4" pots already getting root bound probably won't be a problem but you can always pop them out of the containers and check the root development.

You have what? - another month before you can plant out? If that is the case then I'd wait another 10 days before re-potting if they don't appear to be getting root bound before then.

Question: you say you have 3" tall ones that don't yet have true leaves? If so then they are already leggy and aren't getting enough light. Increase the amount (not length of time but amount) if possible.

Dave

I appreciate the responses! We're due for rain over the next few days, but as soon as it clears I figure I'll start setting them out for a while. I won't be able to plant until...well, frost date is May 15th, but I'll probably wait an extra few days depending on the outlook.

My tall plants do have their true leaves- the few that haven't gotten that far yet are still close to the dirt, so it sounds like all is well.

Guess I'll just keep doing what I'm doing. Every time I mention to someone that I'm starting my own tomato plants I get crazy looks and lots of comments about how it never worked out for them. I'm determined to be the envy of the neighborhood this year. :-)

Note: last year was my first year planting tomatoes, and I put them into large containers. I got nice big plants, but almost no tomatoes. I thought perhaps it was because they didn't get enough sun, so this year I'm putting them where they'll get sun all day.

But earlier this year I pulled one dead plant out of its pot, and I also pulled out the peat pot I'd planted it in. The peat pot was intact, and it looked like the tomato hadn't gotten a chance to get many roots out into the large pot. Effectively it was pot bound in that little peat pot.

This year, if I pot up to peat pots I'm going to make some cuts in it when I plant them in their large outside pots so the roots can get out. That might be why they didn't do very well last year.

My seedlings are about 4 inches tall and looking healthy. I think it's about time they got bigger pots. I couldn't get my Roma seeds to sprout this year, though, so I just went out and bought a Roma plant.

I usually only pot up once before they get planted in the ground. I start them in the Jiffy pellets or six cell starting trays, then about 3-4 weeks, repot them to small styrofoam cups with holes poked in the bottom. They have a few sets of true leaves when I do this. By this time, they are usually ready to spend a fair amount of time outdoors, and I ween them off artificial light. I set them out during the day and bring them inside the garage at night if it's supposed to get below 50. They live very happily in those styrofoam cups until I'm ready to plant. However, I do keep a close eye on the water situation once they get some size to them.
Actually, I just bought cups and potting soil yesterday. I plan on repotting about 50 or so today. I started them from seed on April 1st(and a few as late as April 5) and hope to get them in the ground by the first or second week in May. I usually try to get stuff planted around Mother's day. I was worried I was getting a late start on starting my seeds this year, but they are growing very rapidly and I shouldn't have any problems staying on schedule this year.

I've seen it posted that it is best to repot three times, and I have seen agricultural studies indicating that one pot up gives best results (as opposed to direct seeding). Repotting/potting up damages-disturbes the original taproot causing the plant to produce a more fiberous, wide spread root system, which is good, but every time you disturb the roots by potting up you set the plant back. You only need to disturb the roots once to stimulate the change, and with one pot-up you get two disturbance events, one for the pot-up and one when you put the plant in the ground-container.

Once you get the plant into a 4inch pot, with the stem buried so that adventitious roots can grow from the stem you are set until the plant can be put into its final home outside.

Hope this helps

p.s. One study indicated that potting up the little seedlings into 6" pots was even better than 4" pots, but who has room for that!

I do (and agree) pretty much with what Spiced Ham does. I use 2L plastic coke bottles though as my re-pot...cut off the top 2/3 and discard, drill 5 x 5/16" holes in the bottom outer edges. The benefit is that you can see when they need water and you can watch the root growth to get a better feel for when to finally put them in the ground.

Interesting discussion. I suppose I should re-pot more times than I do. Mine generally go from the seedstarting trays into WHATEVER I have saved up over the year, so they are in all sorts of containers from yogurt cups to Starbucks cups to the bottom halves of quart cream cartons. I also snagged a bunch of 2.5" transplant pots at a house sale recently, and those are all filled with seedlings currently. But 4" pots for everything would just kill me. Too much potting mix for one thing! So I am piling the mix into each container as high as it will go to help the plant out, and giving weak MG drinks here and there while I try to squeak by just a couple more weeks! If you have fewer plants I think the larger pots would probably give you an edge, and you should go for it if you can. I am betting most folks on here do not re-pot three times, though.

3 times isn't uncommon if you germinate in seedling trays. ;) From the tray to a cell pack, from the cell pack to individual containers. From them to the garden or sometimes to an even bigger container.

Multiple transplant has other advantages in addition to the root change mentioned above. It can compensate for plants started to soon by slowing them down. It can also fix the leggy seedlings problem from too little light.

It all depends on the methods you use to germinate and the circumstances under which they are grown.

Dave