Tomato plants are remarkably flexible when it comes to propagation, offering gardeners two distinct and highly effective methods for creating new plants: asexual cloning from cuttings and sexual reproduction from seeds. This versatility allows for the quick duplication of a favorite variety or the preservation of specific genetic lines for future seasons. Both techniques are straightforward, allowing even the novice gardener to easily expand their tomato patch.
Cloning Tomatoes from Cuttings
Propagating tomatoes from cuttings is a method of cloning that produces a plant genetically identical to its parent, offering a significant advantage for duplicating high-performing or rare varieties. The material used for this process is typically a “sucker,” which is a side shoot that emerges in the crotch, or axil, where a leaf meets the main stem. These suckers are often pruned away by gardeners to direct the plant’s energy into fruit production, but they serve as ideal cloning material.
For the best success, select a healthy sucker that is approximately four to six inches long and has not yet started to flower. Before attempting to root the cutting, strip away the lower leaves, leaving only the top two or three small leaves remaining. This preparation prevents the submerged leaves from rotting, which could contaminate the rooting medium.
There are two primary methods for rooting the prepared cutting, both of which take advantage of the tomato plant’s natural ability to produce adventitious roots along its stem. The first method involves placing the stem directly into a glass of plain water, ensuring that no leaves are submerged. New roots will typically appear within one to two weeks, and you should change the water every few days to keep it oxygenated and clean.
Alternatively, you can insert the cutting directly into a small pot filled with a moist, well-draining potting mix, burying the stem up to the remaining leaves. This soil-based method encourages the development of a stronger, more established root system from the start. Whether rooted in water or soil, the new clone will be ready for its next stage of growth once a robust network of white roots has developed.
Starting New Plants from Saved Seeds
Starting new plants from saved seeds is a more traditional method that is necessary for preserving heirloom and open-pollinated tomato varieties. The first step involves selecting fully ripe, healthy fruit from a desirable plant, as the seeds inside must be mature to be viable. Once the fruit is opened, the seeds, along with the surrounding gelatinous pulp, are scooped out into a container.
The critical step in saving tomato seeds is a process called fermentation, which mimics the natural decay of the fruit and removes the germination-inhibiting coating around each seed. This gel-like sac contains chemical inhibitors. To ferment the seeds, add a small amount of water to the pulp mixture and cover the container loosely to allow air exchange, placing it in a warm location for three to five days.
During this time, a layer of mold will form on the surface, and the fermentation action will break down the inhibitory coating. Viable, healthy seeds will sink to the bottom of the container, while the pulp and non-viable seeds float to the top. After the fermentation period, the floating debris is poured off, and the sunken seeds are rinsed thoroughly in a fine-mesh strainer to remove any remaining pulp.
The clean seeds must then be completely dried on a non-stick surface, such as a ceramic plate or coffee filter, in a well-ventilated area away from direct sunlight for one to two weeks. Once completely dry, the seeds can be stored in a labeled, airtight container in a cool, dark location, where they can remain viable for several years. The seeds are then ready to be sown in a seed tray filled with a sterile starting mix, where they will germinate under warm, consistent conditions.
Caring for Newly Propagated Plants
Once a cutting has established roots or a seed has germinated into a seedling, the young plant requires careful management to ensure its successful transition into the garden environment. For both rooted cuttings and seedlings, the next step is often “potting up,” which involves moving the small plant from its initial rooting or germination container into a larger pot, typically four inches in diameter. When potting up tomato plants, you should bury the stem deep into the new container, right up to the level of the first true leaves, as the buried stem will develop even more roots.
The final stage of preparation before transplanting outside is a process called “hardening off,” which slowly acclimatizes the tender indoor-grown plant to the harsher outdoor elements. The hardening off process should take place over a period of seven to ten days. Begin by placing the plants outdoors in a shady, protected location for just one or two hours on the first day, gradually increasing their exposure time each subsequent day.
Over the course of the week, the plants should be introduced to filtered sunlight and then eventually to full sun for a few hours. This gradual exposure allows the plant’s cell walls to thicken and its waxy cuticle layer to develop, preparing it to thrive when it is finally transplanted into the garden.