It is possible to grow tomatoes into the fall season, allowing gardeners to extend their harvest well past the typical summer peak. Successfully achieving a fall crop requires a deliberate and strategic approach that differs significantly from standard summer gardening practices. This effort focuses on managing declining temperatures and shorter daylight hours, necessitating careful planning from the initial planting date to the final methods of season extension.
Timing and Variety Selection
The foundation of a successful fall tomato harvest lies in precise timing, calculated backward from the region’s average first frost date. Gardeners must determine the “Days to Maturity” (DTM) of their chosen variety, then add approximately two weeks as a buffer for slower ripening caused by reduced fall sunlight.
Fall crops require varieties with a DTM of 50 to 70 days to ensure a substantial harvest window before a killing frost. Fast-maturing varieties like ‘Early Girl’ or ‘Stupice’ are popular choices, sometimes maturing fruit in as little as 50 to 55 days from transplanting. Determinate varieties are generally preferred for fall planting.
Determinate plants grow to a predetermined size and set the majority of their fruit simultaneously, providing a concentrated burst of ripening that aligns well with the limited time available. Indeterminate varieties continue to grow and produce until frost, which is less efficient for maximizing fruit set during a short, cool period. Selecting determinate varieties channels the plant’s energy into ripening existing fruit rather than continuous vegetative growth.
Adjusting Cultural Practices for Cooler Weather
As the season progresses toward autumn, routine care for tomato plants must be modified to encourage fruit ripening over plant growth. This involves managing the plant’s nutrient intake, specifically nitrogen. High nitrogen levels promote lush, leafy growth, which is counterproductive when the goal is to shift the plant’s energy toward maturing fruit.
Gardeners should reduce or cease high-nitrogen fertilizers and instead focus on nutrients that support fruit development, such as phosphorus and potassium. A lower-nitrogen feed encourages the plant to finish its life cycle by ripening the remaining green tomatoes.
Watering needs diminish as lower temperatures reduce evaporation. Overwatering in cool, damp conditions can invite fungal diseases, so soil should be allowed to dry slightly more than during summer. Consistent moisture is still necessary, as irregular watering can lead to disorders like blossom end rot. Monitoring for different pest populations that emerge as the weather cools is also important.
Protecting Plants from Early Cold
The primary challenge for extending the fall harvest is protecting plants from the initial, light frosts that signal the end of the warm season. Light frosts occur when temperatures dip to about 32°F (0°C), which is enough to damage foliage and stop fruit production. Simple season extension techniques can often buy several weeks of additional ripening time.
Physical barriers such as lightweight, spun-bond row covers are effective because they trap heat radiating from the soil overnight. These fabrics are permeable to light and water, providing continuous protection from temperatures down to approximately 28°F (-2°C). For isolated protection, individual plants can be covered with plastic cloches or inverted buckets.
Temporary plastic tunnels or cold frames offer a more robust solution, creating a microclimate several degrees warmer than the surrounding air. Any sealed structure must be actively vented during warm, sunny fall days to prevent excessive internal heat buildup that can damage the plants. Monitoring local weather forecasts allows for proactive deployment of these protective measures, maximizing outdoor ripening time.
End-of-Season Management
When a hard, killing frost (below 28°F or -2°C) is forecasted, the focus must shift to salvaging the remaining green fruit. Harvest all tomatoes that have reached a mature size, even if they show no sign of color change. The ability of a tomato to ripen indoors depends on it having reached the “mature green” stage before being picked.
Tomatoes are climacteric fruits, meaning they continue ripening off the vine through the production of the gaseous hormone ethylene. To encourage this process indoors, store harvested green tomatoes in an enclosed container, such as a paper bag or cardboard box. This confinement traps the naturally emitted ethylene gas, accelerating color change.
Adding another climacteric fruit, such as a ripe banana or apple, provides an additional source of ethylene. The ideal temperature range for indoor ripening is between 55°F and 70°F (13°C and 21°C); storage below 50°F compromises flavor and texture. Check tomatoes periodically, removing any that show signs of spoilage.