Tomato plants have the ability to generate roots along their stems, which is why it’s beneficial to plant them deeply. But most plants can’t produce roots from stem tissue. Burying a plant’s stem will usually cause rot or even the death of the plant. As a general rule, a plant should be replanted at the same depth it was growing initially. This holds true whether you’re transplanting zinnia seedling grown in a 6-pack, a shrub in a two gallon pot, or a tree that’s been ball and burlapped.
More Transplanting Techniques
Seedlings will develop best if there is only one plant per pot. Instead of trying to untangle two seedlings that have germinated in the same pot, use a scissors to trim off the unwanted plant. Cut it off right at the soil surface, and you won’t disturb the remaining seedling. Use a small utensil, such as a table knife, to lift the transplants out of their original pots. Hold seedlings by their leaves -- not their stems, as it is easy to crush the delicate stem tissues. Make sure you choose a pot that's wide enough and deep enough for the transplants. A 4-inch diameter pot that is 3-4-inches deep is usually adequate. Don't forget to fertilize your seedlings regularly with a water-soluble fertilizer such as PHC for Seedlings.