Tomato Growth & Temperature

Tomatoes are warm-weather vegetables that cannot tolerate even a light frost.

You can start tomatoes by seed at home, or purchase seedlings from a local garden supply center. In both cases, you can watch your tomato plants grow to maturity in your home garden. The rate of growth and development in tomato plants is closely tied to the overall temperature and general growing conditions for the plants. Tomatoes are warm-weather vegetables, preferring sunny, dry and warm growing conditions.

Frost Tolerance

Tomatoes are warm-weather vegetables, with no tolerance for even a light frost. Tomato plants will not survive in temperatures that are below 50 degrees Fahrenheit. The optimal temperature range for tomato plants is between 75 and 85 degrees Fahrenheit. Tomatoes in very cool or wet conditions will not do well, and will be more susceptible to infections and rot.

Germination

Germination is the first step of tomato plant development. Germination is the period during which a tomato seed becomes active rather than dormant, and produces the first roots and shoots of the plant. The tomato seed will not germinate in temperatures below 50 degrees Fahrenheit. The optimal temperature for germination is between 75 and 80 degrees Fahrenheit. The tomato seed requires light and moisture in order for it to germinate. During optimal germination temperatures, it will take around five to seven days for the seedling to emerge.

Seedling Growth

Seedling development occurs as soon as the cotyledon is visible. The cotyledon is part of the seed embryo, and provides nutrition for the early tomato seedling through photosynthesis. During this time, the tomato plant must receive a minimum of six hours of sunlight daily, and be kept moist and warm. The optimal development temperature is between 75 and 85 degrees Fahrenheit, although tomato seedlings will develop at cooler temperatures, albeit at a slower pace. The cotyledon will appear around three to five days after planting in optimum growing conditions. The seedling will develop its first true leaves within two to three weeks of germination. At this point, the seedling will be about 2 inches high, and will grow approximately 1 inch every week or two.

Harvest

Depending on the type of tomato plant -- if it is a determinate or indeterminate plant -- your tomato plant may set all of its fruit within three weeks. This means that all of the fruit ripens and needs to be harvested within a three-week period. Determinate plants are sometimes bred as early tomato plants, meaning harvest can occur within 60 days or less from the date of transplant. For an indeterminate plant, regular harvesting and pruning will encourage the tomato plant to keep producing fruit for the entire growing season. Indeterminate tomato plants usually need 70 to 80 days after transplanting before the fruit is ready for harvesting.

Warm temperatures are best for producing evenly ripe tomatoes. However, in the cooler weather at the end of the growing season, hang tomato plants upside down with the fruit still attached to encourage green tomatoes to ripen further. Temperatures below 50 degrees Fahrenheit or a light frost will be damaging to tomatoes, regardless of whether they have ripened or not.

References

• University of Missouri; Growing Home Garden Tomatoes; David H. Trinklein; 2010
• University of Illinois Extension: Watch Your Garden Grow: Tomato
• Purdue University; Tomatoes; B. Rosie Lerner; 2001
• University of Arizona: Growing Tomatoes Hydroponically

Resources

• University of Illinois Extension: Illinois Vegetable Garden Guide: Tomatoes