It is not late in the season. In Zone 5 it has just begun. If she carefully seperates the plants they should be just fine. They are over crowded now and will only get worse. Just make sure the soil in not too wet when you seperate the plants from eac other. That is what I would do.

Absolutely not too late. The main plant out date in your zone is Memorial Day week-end and this year the holiday was early. Perfect timing in my mind. If the plants are large and/or leggy they can be planted deep or trenched.

It's not too late to plant out, but how long has she had them in that pot? I'd be afraid the roots are all tangled together and she'd lose all of them trying to separate them. I'd say buy replacements for 3 of them and then cut those 3 off at the soil line (she might have to keep cutting them back) and just let the "MVP" (Most Valuable Plant, whether it's the biggest, rarest, favorite, whatever) grow.

Tomato plants can grow new roots at the slice of a knife (or a trowel). Cut them apart, transplant them where you want them.

You would hurt them more by trying to sort the roots than you will by just dividing the root mass evenly among the plants.

I have never lost a plant or seedling by cutting roots in moving them.

I just had a second thought about your question. My new realization is transplanting two of the four plants is not enough.

The pot does not look like a 15 gallon container to me, and even if it is, I do not believe it is large enough for two "heirloom" tomato plants, which would indicate they are large, indeterminate tomato plants. A 15 gallon pot is not large enough for more one plant of that description.

Also, the pot is not even full! I use 5 gallon pots completely full for determinate plants that only grow 3' high.

This post was edited by tdscpa on Sat, Jun 1, 13 at 5:13

Thanks everyone!

These have been growing for about 5 weeks.
tdscpa..........I didn't even notice that the pot only looks half full! I think I'll tell her to transplant 2, maybe three of them, and pull off the lower leaves of all of them, and use lots more soil.
Thanks!

Even 1 plant in that size pot will struggle.

Dave