Cumulative temperature (GDD) requirements at each growth stage of bell pepper

• GDD calculation formula: GDD = (average daily temperature - reference temperature: Tbase). Total GDD per day is accumulated over the growing period.
• Base temperature (Tbase): For green peppers, 10°C is common [1][2][3][4].
• Optimal temperature: 27-29°C during germination and around 21-27°C for most other growth stages [5][6][7][8].

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Accumulated temperature (GDD) requirements by stage

If there is no direct GDD value for each growth stage, GDD is estimated using (1) the period (number of days) reported in the literature, (2) typical measured average temperature, and (3) Tbase=10°C. The estimation method will also be specified for each stage.

1. Germination stage (Germination)

• Duration: 7 to 14 days
• Typical average temperature: 25°C (suitable temperature for germination; there are also documents with a range of 20 to 30°C)
• GDD calculation: [(25°C - 10°C) × number of days]
  → Estimated GDD value:
  • 7 days = 105GDD (15×7)
  • 14 days = 210GDD (15×14)

Reference: Suitable germination temperature and period [5][6][7][8][9]

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2. Seedling

• Duration: 14-28 days
• Typical average temperature: 22.5°C (20-25°C)
• GDD calculation: [(22.5°C - 10°C) × number of days]
  → GDD estimate:
  • 14 days = 175GDD (12.5×14)
  • 28 days = 350GDD (12.5×28)

Reference: Temperature and number of days during the seedling growing period [6][8][9][10]

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3. Growing season (Vegetative)

• Duration: Usually 6-8 weeks (42-56 days) from transplanting (planting) to flowering
• Typical average temperature: Around 22°C
• GDD calculation: [(22°C - 10°C) × number of days]
  → Estimated GDD:
  • 42 days = 504GDD (12×42)
  • 56 days = 672GDD (12×56)

Reference: Progression of growing season, temperature [8][9][10][11]

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4. Flowering

• The cumulative GDD up to the first flowering is often considered part of the growing season, and the progress from flowering to fruit set and enlargement is also temperature dependent.
• Generally, flowers will bloom 30 to 50 days after planting, and the cumulative GDD will be about 350 to 650 (accumulated from the growing season).

Reference: Reports on flowering and GDD [10][11][12]

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5. Fruit Set/Enlargement

• From flowering to fruit maturation green stage: 28-35 days (temperature fluctuation: 20-25°C)
• GDD calculation: [(22°C - 10°C) × number of days]
  → 28 days = 336GDD
  → 35 days = 420GDD
• Actual measurement example (Japan): Cumulative GDD from flowering to mature coloring in Kanagawa Prefecture (house pepper) is 1,200 to 1,300°C (Tbase=10°C) [13].

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6. Maturation/Coloring

• From the end of fruit enlargement to coloration: 14 to 21 days
• Typical average temperature: 22°C
• GDD calculation: [(22°C - 10°C) × number of days]
  → 14 days = 168GDD
  → 21 days = 252GDD
• Actual measurement example: The above 1,200 to 1,300°C is the cumulative value from flowering to mature coloring, and is the cumulative value until full coloring in Japan (green peppers grown in greenhouses) (Tbase=10°C).

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GDD summary by stage (table)

Stage	Estimated period (days)	Average temperature (°C)	GDD reference temperature	Estimated GDD	References
Germination	7–14	25	10	105–210	[5][6][ 7][8][9]
Seedling raising	14–28	22.5	10	175–350	[6][8][9][10]
Growth	42–56	22	10	504–672	[8][9][10][11]
Flowering	30–50 (After planting)	22	10	350–650 (cumulative)	[10][11][12]
Fruit enlargement	2 8–35	22	10	336–420	[10][11][13]
Maturity/Coloration	14–21	22	10	168–252	[10][11][13]
Flowering to coloration total	49–56	22	10	Approx. 1,200–1,300	[13]

Try it in your region

See how these GDD requirements apply to your local weather data. Simulate Bell pepper cultivation →

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Differences and points to note depending on region and cultivation method

• These values are based on a standard temperature of 10°C and average open field or facility (house) conditions.
• The number of days and GDD may vary depending on the local climate and cultivation type (outdoor/house).
• Domestic example (Kanagawa Prefecture, greenhouse cultivation): Approximately 1,200–1,300 GDD from flowering to mature coloring [13].
• Estimates from overseas also show a similar range, with Tbase and temperature differences being the main fluctuation factors.

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Details of GDD estimation method

1. For the period (number of days) of each growth stage, refer to the values ​​reported in the literature.
2. The appropriate average temperature (temperature range) for each stage is set based on physiological and ecological tests, cultivation instructions, etc.
3. The standard temperature (Tbase=10°C) is based on domestic and international cultivation guidelines and academic reports.
4. GDD = (average temperature - 10°C) × period (number of days) estimated for each stage.
5. If the average daily temperature is less than 10°C, that day is considered 0GDD.

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Overview

The cumulative temperature requirement (GDD) for each growth stage of green pepper is estimated and reported as follows, based on a reference temperature of 10°C:

• Germination : 105–210GDD
• Seedling: 175–350GDD
• Growing: 500–700GDD
• Flowering: 350–650GDD (cumulative)
• Fruiting/enlargement: 340–420GDD
• Maturity/coloration: 170–250GDD
• Blooming to total coloring: Approximately 1,200–1,300 GDD (Kanagawa prefecture facility reference value)

Since the cumulative temperature at each stage varies depending on weather conditions and cultivation environment, we recommend on-site observation or the use of local guidelines.

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Sources

[1] MRCC: Growing Degree Day Description: https://www.mrcc.purdue.edu/resources/growing-degree-day-description
[2] Vegetable degree-day models: An introduction for farmers and gardeners (OSU): https://extension.oregonstate.edu/catalog/em-9305-vegetable-degree-day-models-introduction-farmers-gardeners
[3] Growing degree-days: one equation, two interpretations: https://digitalcommons.unl.edu/usdaarsfacpub/83/
[4] About Growing Degree Days - GreenCast | Syngenta: https://www.greencastonline.com/growing-degree-days/learn-more
[5] Growing Sweet Peppers in Missouri: https://marshydro.eu/blog/bell-peppers-growing-stages/
[7] Bell Pepper Plant Growth Stages (PepperGeek): https://peppergeek.com/bell-pepper-plant-growing-stages/
[8] 6 Bell Peppers Growing Stages (SpiderFarmer): https://spiderfarmer.ca/bell-peppers-growing-stages/
[9] Growing Peppers in a Home Garden (Univ. of Maryland): https://extension.umd.edu/resource/growing-peppers-home-garden
[10] Growth, Physiological, and Biochemical Responses of Ethiopian Capsicum annuum: https://pmc.ncbi.nlm.nih.gov/articles/PMC9840558/
[11] Growing Peppers | Extension | West Virginia University: https://extension.illinois.edu/blogs/prairies-perennials/2020-08-13-growing-and-using-peppers
[13] Varieties and physiological and ecological characteristics of colored bell pepper (Paprika) (Kanagawa Prefecture): https://www.pref.kanagawa.jp/documents/27252/531907.pdf