Seed starting mix is intended to behave just as you're describing, fall easily away from the roots to minimize damage to the roots when transplanting. Why do you want the soil to behave any differently? The mix in what you would buy as a nursery plant is a potting soil, probably blended with some perlite or similar. Also, those plants are bigger and have more developed root systems, which holds the soil together. You can use regular potting soil for potting up your seedlings, if you don't want to continue to use seed starting mix. Sorry if I'm not addressing your question correctly, I guess I don't really understand why this is a problem.

Don't panic!!

Was your mix wet. Never mind. Your plants roots hadn't settled into the mix yet. When you transplant make sure the mix is wet right through but not sopping. I wet mine through in a tinfoil roaster before I put it in the pots.

You can sink tomatoes lower in the mix than it was in the pellet. Press down on the mix a bit around the plant, to set and compact the soil a bit around the plant. The roots have to grow into the mix. When they are planted out water before you try to take them out of the pots.

Personally I use promix as do most greenhouses

Ok, I guess I am confused then, because I thought they were saying that when they turned over the old, smaller container to dump out the seedling, all the seed starting mix just fell away from the seedling. Not that the soil was too 'loose' in the new pot.

It was in my attempt to transplant to a larger pot. Oilpainter is suggesting I wet the soil before trying to re-pot. I was thinking my transplant to a larger container would be like trying to plant a store bought plant, which now I think I understand is a "potting soil", not seed starting mix. This is my 1st attempt at seed starting more than just a few plants. I haven't killed anything yet, but trying to keep them going till a little warmer outside. Thanks

jim,

Don't worry about it. Tomato plants are actually very hardy. Plant them down as low as the seed leaves "cotyledons" (and remove them before replanting) and the plant will grow roots out the length of the stem that is under the soil. This process will actually lead to stronger, healthier plants in the long-run!