If you’ve not yet planted your tomato plants out into the garden, let me share a little tip with you. With most other plants, you want to set the plant in the earth so that the soil level of the potted plant is at the same level as your garden soil. Tomato plants, however, like to be planted deeper than that. Go ahead and dig a hole deep enough to allow the main stem to be buried up to the first set of leaves. My tomatoes have all been planted out, but through the miracle of technology and with the aid of my son, I have a little graphic example for you.
See that brown line? (Click through for a larger image.) That’s where the soil level should be when you plant the tomato. The tomato will send out little roots from that stem, making the plant much more stable in the ground and giving it more opportunities to pull up nutrients.
If you have a really leggy tomato plant, you can even lay the plant in a horizontal hole, covering most of the stem but allowing the top of the plant to emerge above the level of the soil. It will look crooked for a week or so, but will very quickly begin to grow straight.