I recently stumbled upon a fairly simple method for growing tomato plants from cuttings. It happened by accident when I unintentionally knocked off a tomato branch. Because I felt bad about the plant trauma, I put the broken branch in water. Turns out that roots grew from the cutting.
The following are steps/details for this technique to help optimize your growing success. This is a great option if you want to grow lots of tomato plants… esp from branches that you may have trimmed off anyways in the process of training your plants.
Cut a growing branch from a healthy tomato plant. Making a clean cut is probably a good idea. However, I discovered on my first attempt that it didn’t matter how clean the branch cut/break was.
Trim back lower branches and flowers/fruit to redirect energy to root growth. Also cut off any sad looking-yellowing or browning branches. A good overall length/height for a cutting seems to be about 6-8 inches.
Put the cut end of the branch in a container of clean water. No need to add any growth hormones or other chemicals. Replace the water when needed to keep it clean. Put the cutting in bright shade. Having the tomato cutting located by the kitchen sink makes it easy to regularly monitor and address water issues when indicated.
Wait for a good root ball to form (it typically takes a few weeks). Don’t feel bad if it doesn’t work; its not 100%, but it works more often than not. Doing a bunch of cuttings at once increases the chances for success.
When the root ball is robust looking, remove the cutting from the water. Cut back lower leaves and branches to reduce evaporation stress related to root-maturity discordance.
Carefully untangle the roots. Gently place your rooted-cutting deep into a container and fill in with additional soil to cover all the roots as well as several inches of the stem above. This deep planting technique will encourage additional root growth above the existing root ball and also promote stability of the plant.
Stake the plant for stability. I like to use the green-Velcro adjustable plant ties to secure the plant in place because it is just easy and forgiving. However, natural fiber string etc, works great too. Then water the heck out of your new transplanted tomato plant.
Place newly planted cutting/plant in cool bright shade and keep the soil moist. After a few more weeks, you should see new growth. At this point move to partial shade/sun and then full sun. Congrats on a new cloned plant!
As a side; there are so many awesome/tasty heirloom tomatoes that are perfect for home growing. One of my favorites is the Purple Cherokee tomato. Its definitely worth trying out if you see the seeds in your local seed store.
Also; a similar process of cloning works great for propagating rosemary plants (with a few specific modifications). For more info about that technique, see link for specific details on easy rosemary propagation.