Whether it is an heirloom, prolific producer, or just a favorite variety you want another plant of, propagating another tomato plant from one of the plant's stems is quite doable. Not only will you be growing a duplicate plant of the parent, you will be getting a head start on the production of tomatoes. Cuttings have a six to eight week head start on growing a tomato plant from seed. Propagating a cutting for a tomato is so easy, even a novice gardener will have success.
Sterilize your pruning shears with a solution of 50 percent water and 50 percent bleach, to kill any bacteria that might be on them. Wash the cutting blades off with the bleach solution and rinse them off with clean water.
Cut a six-inch tip from the tomato plant right above a leaf terminal. Trim off all the leaves except the top two. Trim off any flowers or buds from the cutting.
Fill a small jar with approximately three inches of water. Place the cutting inside of the jar and set the jar in a kitchen window, or outside in an area that receives indirect light and is warm. Fill the jar with fresh water once per week.
Remove the cutting from the water in approximately two weeks, after a root system has developed. Allow the roots to grow to at least two inches in length before transplanting into soil.
Fill a four-inch container with a well draining potting mix. Water the container to moisten the soil and allow it to settle. Stick your finger into the center of the container and make a two-inch deep hole.
Stick the tomato cutting into the hole, being careful not to damage its root system. Cover the hole with soil and lightly firm it up around the stem.
Water the cutting again. Keep the container's soil moist, but not soggy. Place the container in an area that gets indirect light and not full sunlight. Gradually harden the cutting to sunnier conditions over a period of two weeks. Transplant into the garden, once the cutting has established itself inside the container.