Comprehensive Report on Growing Degree Day (GDD) Requirements by Growth Stage for Tomato

Overview

This report surveys the Growing Degree Days (GDD) required for each growth stage of tomato (germination to seedling, vegetative growth, flowering and fruit set, and fruit enlargement and maturation), based primarily on data from Japanese agricultural experiment stations, government agencies, and academic papers, organized as much as possible from primary sources. Where direct GDD values were unavailable, estimates were made using the number of days, measured temperatures, base temperature (lower threshold for effective accumulated temperature), and optimal temperature. Key uncertainties in the findings are also discussed.

GDD Fundamentals and Reference Values for Tomato

• GDD is a key indicator for evaluating crop growth progress, calculated by subtracting the base temperature from the daily mean temperature and summing these values over the number of days in each growth stage.
• In many Japanese and international publications, a base temperature of 10°C is commonly used for tomato; however, recent domestic research has calculated different base temperature thresholds for each cultivar and growth stage, and it is recommended to use these specific values for precise management in cultivation settings [1][2][4][5].

GDD Requirements Summary by Growth Stage for Tomato

1. Germination to Seedling Stage

• Optimal temperature range: approximately 20–25°C
• Base temperature: 10°C
• Duration: 6–8 days (typical Japanese tomato varieties)
• Direct GDD values: no clear documentation in Japanese or international literature
• Estimation method:
  • GDD = (mean temperature − base temp) × days
  • Example: 22°C (mean) − 10°C = 12°C × 7 days ≈ 84°C·days
• Uncertainty: highly dependent on actual temperature, humidity, and other environmental factors; variations of approximately 20–30% may occur depending on cultivar and cultivation system [6][9].

2. Vegetative Growth Stage

• Optimal temperature range: day 25–28°C, night 15–17°C
• Base temperature: 10°C
• Duration: 25–35 days (including the domestic seedling-raising to transplanting and stem growth period)
• Direct GDD values: no definitive figures available
• Estimation method:
  • Assuming mean temperature of 22°C: (22°C − 10°C) × 30 days = 360°C·days
  • Adjusted values (significant difference between open-field and greenhouse): approximately 400–500°C·days as a guideline
• Uncertainty: variation exists due to differences in growing environment (day length, nutritional conditions), cultivar, and management practices. Some Japanese studies have used a base temperature of 13.2°C for the stem growth period [1][5][9].

3. Flowering and Fruit Set (Reproductive Stage)

• Optimal temperature range: 15–26–30°C
• Base temperature: varies by Japanese cultivar, with reports ranging from 10°C to 13.2°C
• Key reported values:
  • Cultivar ‘Rinka 409’: 220°C·days for truss interval (time to next truss flowering) (base temp 13.2°C) [1]
  • International models: examples exist of predicting early flowering using GDD (base temp 10°C), treated as the midpoint of the total GDD period
• Estimate: cumulative GDD to flowering for the above cultivar corresponds to approximately 1/3 to 1/2 of the total (see fruit enlargement and maturation stage below)
• Uncertainty: it has been noted that even within Japan, the accumulated temperature for inflorescence formation and flowering detection varies by cultivar and management environment, and direct values are extremely rarely documented in the literature [1][4][5].

4. Fruit Enlargement and Maturation Stage

• Optimal temperature range: 18–27°C
• Base temperature: varies by cultivar in Japanese field studies (e.g., Rinka 409 = 13.2°C, TY Misora = unknown, House Momotaro = unknown); 10°C is generally used
• Key reported values:
  • Kanagawa Agricultural Technology Center: onset of coloring at 841°C·days, full ripening (a*21 attainment) at 959°C·days (effective accumulated temperature, base temp estimated at 10–13°C) [2]
  • Tokyo Smart Agriculture: approximately 1,000°C·days from flowering to first harvest, harvest period 270°C·days (±100°C·days variation depending on cultivar) [1]
  • International large-fruit cultivation: 1,700–1,850°F·days from flowering to ripening (approximately 944–1,028°C·days, base 50°F/10°C) [4]
• Analysis:
  • Both Japanese and international sources converge on GDD values of approximately 950–1,000°C·days from flowering to maturation/harvest
  • Variation among domestic cultivars (full ripening: 841–1,008°C·days)
• Uncertainty: individual and environmental variation arises from fruit position, temperature fluctuations, and precision of environmental control [2].

5. Overall GDD Estimate (Reference: Sowing to Harvest)

• Japanese and international literature frequently cite approximately 2,000°C·days from sowing to harvest (assuming base temp 10°C) [3][4].
• ISHS report on cultivar 'Cal j': 2,055–2,248°C·days from sowing to harvest (base temp 6°C) [3].

Comparison and Supplementary Notes on Domestic and International Literature Values and Estimates

• Range where direct GDD values were obtained: in Japan, GDD values from post-flowering to ripening (841–1,008°C·days) have been closely verified at the agricultural experiment station level (with clear definitions for full ripening and coloring). On the other hand, GDD values for early stages such as germination, vegetative growth, and flowering/fruit set remain largely estimates.
• Validity of estimation methods: the relationship between days, base temperature, and accumulated temperature is largely standardized both domestically and internationally, and the general method of “days per stage × (mean daily temperature − base temp)” is widely accepted [6][9][10][11].
• Cultivar and environmental factors: recent Japanese research (e.g., Tokyo Smart Agriculture Project) emphasizes that even within the same facility, the effective accumulated temperature “threshold (base temp)” differs by cultivar, and GDD guidelines can deviate by approximately 50–100°C·days [1][2].

Key Uncertainties and Considerations

• Differences in base temperature: in practice, 10°C or the base temperature reported in major studies is used, but this may vary by several degrees depending on the target cultivar and stage.
• Growing environment and management methods: since the number of days and accumulated temperature itself can fluctuate depending on environmental conditions such as greenhouse vs. open-field and the presence or absence of temperature control, it is desirable to operate with some flexibility for field adaptation.
• Fragmentary nature of literature values: official Japanese reports where GDD is clearly organized by stage are rare (especially for germination to vegetative stages). Conversely, well-supported values have been obtained for post-flowering to full ripening.

Summary Table

Growth Stage	Base Temperature	Optimal Temperature (Guideline)	Days (Guideline)	Estimated/Reported GDD (Guideline)	Source Examples
Germination to Seedling	10°C	20–25°C	6–8 days	80–100°C·days (estimated)	[6][9]
Vegetative Growth	10°C	15–28°C	25–35 days	350–500°C·days (estimated)	[5][9]
Flowering/Fruit Set (truss interval)	13.2°C (example)	15–26°C	Example: several days to 1 week	220°C·days (truss interval/cultivar example)	[1]
Fruit Enlargement/Maturation	10–13.2°C	18–27°C	20–40 days	841–1,008°C·days (full ripening/onset of coloring)	[1][2][4]
Sowing to Harvest (overall reference)	6–10°C	20–28°C	120–180 days	~2,000°C·days (overall guideline)	[3][4][5]

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Conclusion

• Regarding the GDD (accumulated temperature) required for each growth stage of tomato, values for germination to seedling and vegetative growth stages are estimates from the literature; however, for the fruit enlargement and maturation stage, detailed observations and numerical reports from domestic experiment stations provide practical values with clear cultivar-specific ranges.
• Accumulated temperature management, while accounting for individual variation due to cultivar characteristics and field-level precision, can serve as an adequate tool for growth management and optimal harvest timing prediction within the range of domestic and international standard values.
• Particularly in greenhouse horticulture, utilizing base temperature and accumulated temperature management based on domestic research enables more precise production planning than conventional methods.
• The estimated accumulated temperature values for each stage have significant potential to become more detailed and cultivar-specific management indicators as cultivar-specific data are expanded in the future.

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Sources

[1] Tomatoの生育制御・栽培管理の合理化に向けた有効積算温度モデルの構築（東京スマート農業プロジェクト報告書 PDF）: https://www.tokyo-aff.or.jp/uploaded/attachment/9095.pdf
[2] Tomato果実の成熟に伴う果実表面色の変化と積算温度の関係の解明（神奈川県農技センター PDF）: https://www.pref.kanagawa.jp/documents/95322/5102nougi19.pdf
[3] GROWTH AND DEVELOPMENT OF TOMATO 'Cal j' (ISHS): https://www.ishs.org/ishs-article/100_20
[4] Growing Degree Days - Dr. Marv Meisner's Giant Tomatoes: https://www.giantpumpkin.com/TomatoEbook/c28.html
[5] How to Use the Tomato Growing Degree Day Model（Oregon State University): https://blog.pestprophet.com/how-to-use-the-tomato-growing-degree-day-model/
[6] Tomato Growth Stages: From Germination To Ripening（EOS Crop Management Guide）: https://eos.com/crop-management-guide/tomato-growth-stages/
[7] Determination of developmental and ripening stages of whole tomato fruit (BMC Plant Biology): https://bmcplantbiol.biomedcentral.com/articles/10.1186/s12870-019-1852-5
[8] Flowering tomato plant growth stages - Nutrition Program (Haifa Group): https://www.haifa-group.com/haifa-blog/flowering-tomato-plant-growth-stages-nutrition-program
[9] Tomato Plant Growth Timeline: 7 Stages (With Pictures) - The Spruce: https://www.thespruce.com/tomato-plant-growth-timeline-7255375
[10] Base and upper temperature thresholds to support the calculation of crop development (Agricultural Water Management, 2025): https://www.sciencedirect.com/science/article/pii/S037837742500469X
[11] Vegetable degree-day models: An introduction for farmers and gardeners (OSU Extension): https://extension.oregonstate.edu/catalog/em-9305-vegetable-degree-day-models-introduction-farmers-gardeners