Any part of the tomato stem that's covered with soil will develop roots, and a large root system is important for transplants. Try using a deeper container and set the plants lower than they were growing before - right up to the lowest set of leaves, if you can. Use the same soil mix that you used to start your seeds. Here are some hints for successful repotting:
Before the tomato plants can be transplanted successfully to the garden, they need to develop strong root and top growth. To be sure their seedlings have a good root system, many gardeners prefer to repot them a second time before setting them out in the garden. Wait until seedlings are six to 10 inches tall. A good rule is to transplant when the height of your seedling is three times the diameter of its pot. Pot them up individually in half-gallon milk cartons or four- to six-inch-diameter pots. Again, you can plant them right up to their first set of leaves.
If your seedlings are getting tall and spindly, the room temperature may bee too high, the light too weak, or you're using too much fertilizer (or a combination of all three). Review seedling needs in Starting Tomatoes from Seed and adjust growing conditions as needed. Transplanting leggy seedlings deeply helps them to root along their stems, thus reducing the problem, but the best solution is to give your young plants proper growing conditions in the first place.
|1. Choosing Tomato Varieties|
|2. Starting Tomato Seeds|
|3. Repotting and Transplanting Tomato Seedlings ← you're on this article right now|
|4. Hardening Off Tomato Transplants|
|5. Garden Prep for Tomatoes|
|6. Container Tomatoes|
|7. The Great Tomato Race|
|8. Tomato Essentials|