Creating new plants from stem cuttings produces new plants identical to the mother plant. Although stem cuttings are typically used to propagate houseplants or to create new plants from annuals that have grown outside during the summer, it is an effective way to clone a tomato plant. Once the cutting is rooted and potted in soil, it can be moved outside for the summer or grown inside under plant lights during the winter.
Select a 4- to 6-inch terminal end of healthy young growth. Look for any signs of insect damage or discolored leaves or stem. The stem should be firm, but supple. Dry hardened stems do not root well.
Cut just below a leaf node where the leaf grows from the stem, as this area is rich with growth agents that speed root formation. Remove leaves from the bottom 2 inches of the stem.
Place the stem cutting in a vase or glass jar filled with of water. Although it is not necessary, clear glass is preferred as it allows you to observe root formation.
Set in a bright window and watch for roots to appear. Rooting time depends on the cultivar, temperature and age of the cutting. Roots appear within a week or two.
Change water if it becomes stagnant and refill to maintain an even level as water evaporates.
Plant in a mixture of equal parts potting soil, peat moss and perlite, once roots are established and new growth appears.
Place in bright indirect light and keep soil evenly moist. Gradually move the plant to more sun until it tolerates full sun with no signs of wilt or faded leaves.
Water when soil dries and apply water soluble fertilizer on a 14-day schedule to promote lush new growth.
Plant outside after the danger of frost.