The autumn frost marks the end of the outdoor growing season for the warmth-loving tomato plant, but it does not have to signal the end of your harvest or favorite variety. Winterizing tomato plants is the proactive process of protecting them from freezing temperatures, which can damage or kill the plant and its fruit in a single night. Success requires acting decisively before the first hard frost, which occurs when temperatures drop below 32°F (0°C). By implementing specific techniques, you can extend the life of a mature plant, preserve the genetics of a desirable variety for the next season, or ripen the final bounty of green fruit.
Overwintering the Whole Plant Indoors
Bringing a mature tomato plant inside allows you to keep a favorite variety alive indefinitely, though this process is typically reserved for plants grown in containers. Before the move, the plant requires severe pruning to manage its size and shift it into a semi-dormant state. Cut back the main stems significantly, leaving only a few healthy branches approximately 1 to 2 feet long, and remove all flowers and developing fruit. This heavy pruning redirects the plant’s energy away from production and focuses it on survival.
A thorough inspection for pests is necessary before relocating the plant indoors, as common garden pests like whiteflies and spider mites can rapidly infest your home. Examine the undersides of the remaining leaves and treat any signs of infestation with insecticidal soap or neem oil. Once inside, place the plant in a cool location where temperatures remain consistently between 50°F and 65°F (10°C and 18°C) to mimic a mild winter.
A mature tomato plant requires supplemental lighting to thrive indoors during the shorter days of winter. Natural light from a window is usually insufficient, so provide 12 to 16 hours daily of light from a dedicated grow light to prevent the plant from becoming leggy. During this period of reduced growth, the plant’s need for water decreases drastically. Allow the top inch of soil to dry out completely between waterings, perhaps only once every two weeks, to avoid root rot.
Starting New Plants from Cuttings
A simpler, more space-efficient method to save a treasured variety is by propagating small clones from cuttings, which are genetically identical to the parent plant. Select a healthy, non-flowering sucker or side shoot approximately 4 to 8 inches in length, taking the cutting with a sharp, clean tool. These small shoots are ideal because new roots readily form from the tiny hairs along the stem, making tomatoes exceptionally easy to clone.
The cuttings can be rooted using two primary methods for successful propagation. One option is to place the cut end into a glass of clean water, ensuring no leaves are submerged; roots often appear within a week. Alternatively, plant the cutting directly into a small pot filled with a sterile, moist potting mix, which eliminates the stress of later transplanting.
Once roots have developed to about an inch long, or the cutting shows stable new growth in the soil, transplant it into a small container. These young plants require bright light, similar to seedlings, and benefit from being placed under a grow light for 12 to 16 hours daily. Maintaining these small, manageable clones throughout the winter allows you to plant them out early the following spring, often resulting in an earlier harvest than plants started from seed.
Salvaging the Green Harvest
As the threat of frost approaches, any fruit remaining on the vine must be salvaged, since temperatures below 32°F will damage the tomatoes, causing them to turn soft and mushy. Inspecting the fruit for maturity is important, as only full-sized green tomatoes that have not yet begun to blush will ripen successfully indoors. Gently twist or cut the fruit from the vine, making sure to handle each tomato carefully to avoid bruising or puncture wounds.
Ripening the harvest indoors relies on the natural release of ethylene gas from the fruit. A highly effective method is to place the unblemished tomatoes in a single layer inside a cardboard box or a paper bag, which concentrates the gas around the fruit. Placing a ripe apple or banana alongside the tomatoes can further accelerate the ripening process due to their higher rate of ethylene production.
Slow Ripening Methods
For slow, steady ripening, individual tomatoes can be wrapped in newspaper and stored in a cool, dark location, such as a basement or garage. The ideal storage environment should be around 55°F to 70°F (13°C to 21°C) and slightly humid. Never refrigerate the tomatoes, as cold temperatures will degrade the texture and mute the final flavor. Check the stored tomatoes every few days and promptly remove any that show signs of mold or rot to prevent the spread of decay to neighboring fruit.