Tomato (Solanum lycopersicum) — Comprehensive Temperature Requirements by Growth Stage

Overview

This report organizes the temperature requirements for tomato (Solanum lycopersicum) cultivation by each growth stage: germination/seedling, vegetative growth, flowering/fruit set (reproductive growth), and fruit enlargement/ripening.
For each stage, the following temperature parameters (as defined below) are summarized.

optimal_min, optimal_max (optimum minimum/maximum temperature)
base_temperature (growth initiation/GDD base temperature)
low_stress_threshold (low-temperature stress threshold)
high_stress_threshold (high-temperature stress threshold)
max_temperature (maximum temperature)
frost_threshold (frost damage threshold)
sterility_risk_threshold (sterility risk threshold; null for non-flowering stages)

For each parameter, reliable Japanese primary literature and official agricultural guidance materials are referenced as the primary sources; English primary and public extension service materials supplement where necessary.
In cases where clear evidence is insufficient for specific parameter values or stages, supplementary knowledge from related solanaceous crops (e.g., eggplant) is also noted.

1. Parameter Definitions (Recap)

optimal_min, optimal_max: Optimum minimum and maximum temperatures for vigorous germination and growth
base_temperature: Growth initiation temperature (below which GDD is not accumulated)
low_stress_threshold: Low-temperature threshold at which growth inhibition begins
high_stress_threshold: High-temperature threshold at which growth inhibition begins
max_temperature: Maximum temperature at which growth/germination ceases
frost_threshold: Critical temperature at which frost damage occurs
sterility_risk_threshold: High-temperature sterility risk threshold (applicable only to flowering/fruit set stage; — for other stages)

Temperature Parameters by Growth Stage

Growth Stage	optimal_min	optimal_max	base_temperature	low_stress_threshold	high_stress_threshold	max_temperature	frost_threshold	sterility_risk_threshold (flowering only)	References
Germination–Seedling	18°C	29°C	10°C	12–13°C	32°C	34°C	0°C	—	[1][2][3][4][5]
Vegetative Growth	15–17°C (night)	25–28°C (day)	10°C	10–12°C	30–35°C	38°C	0°C	—	[13][14][15][16][17][18]
Flowering/Fruit Set (Reproductive)	15°C	26–30°C	10°C	13–15°C	30°C	35–40°C	0°C	32–35°C (day), 21°C (night)	[19][20][21][22][23][24]
Fruit Enlargement/Ripening	18°C	27°C	10°C	13°C	30–32°C	35°C	0°C	—	[25][26][27]

(*Note: For the fruit enlargement to ripening stage, optimal conditions and stress thresholds largely overlap with those of the flowering stage; details are supplemented below.)

3. Detailed Explanation by Growth Stage

3-1. Germination to Seedling Stage

optimal_min / optimal_max: 18°C–29°C. The highest germination rate and shortest germination time are around 25°C. This range is recommended for both day and night [1][2][3][4][5].
base_temperature: 10°C (below this, germination and growth barely progress; also used for GDD calculation) [6][7][8].
low_stress_threshold: Below 12–13°C, growth slows markedly and the risk of cold/chilling injury increases [2][3][9][10].
high_stress_threshold: Above 32°C, germination rate and seedling survival decline (physiological disorders in seeds and embryos increase) [2][5][10].
max_temperature: At 34°C or above, germination virtually ceases and growth becomes impossible [4][10].
frost_threshold: 0°C is lethal. Seedlings die in frost-prone environments [9][11][12].
sterility_risk_threshold: Not applicable at this stage (null) [3][10].

Note: The above parameters are well supported by multiple domestic and international primary sources and extension materials, and the values have high reliability.

3-2. Vegetative Growth Stage

optimal_min / optimal_max: Daytime 21–25°C, nighttime around 15–17°C is the recommended range (up to 28°C is tolerable under direct sunlight). Growth inhibition becomes pronounced outside the optimal range [13][14][15][16][17][18].
base_temperature: 10°C (same as for germination) [15][16].
low_stress_threshold: At 10–12°C, growth and root function decline significantly. When nighttime temperature drops below 15°C, root and stem metabolic activity also decreases [16][19].
high_stress_threshold: Stress becomes pronounced above 30–35°C (daytime). Above 35°C, water deficit and physiological disorders expand [20][21][22].
max_temperature: Growth ceases above 38°C [21][22].
frost_threshold: Direct damage at 0°C; chilling injury risk below 5°C [11][12][13][15].
sterility_risk_threshold: Not applicable at this stage (—) [15].

Note: Values are consistent across many official sources including the Japan Natural Farming International Research and Development Center, Japan Soil Association, and overseas university extension services.

3-3. Flowering and Fruit Set (Reproductive Stage)

optimal_min / optimal_max: Optimal flowering and fruit set occur at 15–26°C. Nighttime 15°C, daytime up to 30°C maximum. Beyond this, reproductive disorder risk increases sharply [23][24][25][26][27][28].
base_temperature: 10°C (consistent throughout all growth stages; same for flowering) [7][28].
low_stress_threshold: Below 13–15°C (night), pollen maturation and fruit set rate decline significantly. Cold stress increases parthenocarpic and malformed fruits [24][25].
high_stress_threshold: Above 30°C (daytime), pollen and stigma damage begins to increase. Above 35°C, pollination and fruit set become nearly impossible [23][24][25][29].
max_temperature: 35–40°C (clear fruit set failure at 36°C; cell necrosis of reproductive organs near 40°C) [24][25][29].
frost_threshold: 0°C causes lethal necrosis of flowers and young fruits. Strict frost avoidance is essential during open-field flowering [16][30].
sterility_risk_threshold: Above 32–35°C (daytime) and/or above 21°C at night, pollen germination capacity and fertilization ability decline sharply (high sterility risk) [24][28][31].

Note: The flowering and fruit set stage is physiologically the most temperature-sensitive, with sterility risk and malformed fruit frequency varying dramatically. This is well documented in Japanese MAFF and prefectural materials as well as international papers and patent literature.

3-4. Fruit Enlargement and Ripening Stage

optimal_min / optimal_max: Optimal is 18–27°C (day/night average). Day-night temperature balance is important for fruit enlargement and ripening [13][32].
base_temperature: 10°C (consistent across all stages) [6][7].
low_stress_threshold: Below 13°C, enlargement rate decreases, suggesting chilling injury [15][32].
high_stress_threshold: Above 30–32°C, fruit discoloration occurs (lycopene synthesis stops) and sunscald risk increases [32][33].
max_temperature: Above 35°C, fruit growth stops and malformed/physiologically disordered fruits become prominent [32][33].
frost_threshold: 0°C. If this temperature is reached before full ripening, fruit tissue is damaged and taste and appearance quality decline [16][30].
sterility_risk_threshold: Not applicable (null) [32].

Note: Detailed by the Japan Soil Association and overseas university extension services. Attention to day-night temperature range and high-temperature disorders is particularly important for fruit coloring and quality.

4. Basis and Supplementary Notes for Parameter Values

base_temperature (10°C), optimal_min (around 15–18°C), and optimal_max (25–29°C) are all consistent across multiple agricultural guidance materials and guidelines from germination through flowering to ripening [1][6][7][13][18].
low_stress_threshold and high_stress_threshold are set based on actual weather disaster and physiological disorder cases and agricultural experiment station reports. In particular, 35°C and nighttime above 21°C are the critical thresholds for sterility during flowering and fruit set [24][28][31].
Values are consistent across domestic guidance materials (Japan Soil Association, MAFF, prefectures) and overseas university extension services (UC Davis, Virginia Tech, Penn State, etc.).
Frost damage threshold is consistently 0°C. There are also many descriptions of chilling and frost damage risks [11][12][30].
As supplementary information, eggplant and bell pepper have broadly similar temperature systems, but tomato-specific experimental and trial data are given priority for key parameter values.

5. Reference Table (All Stages Summary)

Stage	optimal_min	optimal_max	base_temp	low_stress	high_stress	max_temp	frost	sterility_risk
Germination/Seedling	18°C	29°C	10°C	12–13°C	32°C	34°C	0°C	—
Vegetative Growth	15–17°C	25–28°C	10°C	10–12°C	30–35°C	38°C	0°C	—
Flowering/Fruit Set	15°C	26–30°C	10°C	13–15°C	30°C	35–40°C	0°C	32–35°C/21°C
Fruit Ripening	18°C	27°C	10°C	13°C	30–32°C	35°C	0°C	—

6. Summary

Clear recommended values and thresholds for temperature requirements at each growth stage of tomato are defined by official domestic and international sources.
Adaptation management for fluctuating weather conditions — especially the increasing risk of high temperatures in recent years — is critical, and countermeasures against high-temperature sterility during flowering and fruit quality disorders remain the most significant challenges in cultivation management.

Tomato (Solanum lycopersicum) — Comprehensive Temperature Requirements by Growth Stage ​

Overview ​

1. Parameter Definitions (Recap) ​

Temperature Parameters by Growth Stage ​

3. Detailed Explanation by Growth Stage ​

3-1. Germination to Seedling Stage ​

3-2. Vegetative Growth Stage ​

3-3. Flowering and Fruit Set (Reproductive Stage) ​

3-4. Fruit Enlargement and Ripening Stage ​

4. Basis and Supplementary Notes for Parameter Values ​

5. Reference Table (All Stages Summary) ​

6. Summary ​

Sources ​