Detailed summary of temperature requirements at each growth stage of cucumber (cucumber)

Overview

Cucumber (Cucumis sativus) prefers a warm environment, and proper temperature control is essential at each growth stage (germination, seedling, flowering, and fruiting). In this report, we organize the following temperature parameters for each growth stage based on Japanese academic and horticultural materials and international research literature, and report any cases where there are multiple definitions or differences in values.

optimal_min (optimal minimum temperature)
optimal_max (optimal maximum temperature)
base_temperature (base temperature)
low_stress_threshold (low temperature stress threshold)
high_stress_threshold (high temperature Stress threshold)
max_temperature (maximum allowable temperature)
frost_threshold (frost damage threshold)
sterility_risk_threshold (flowering period only: sterility risk threshold)

If the definition is ambiguous or cannot be found in the literature, this should also be stated.

1. Temperature requirements for germination period

Organization of germination period parameters

optimal_min/optimal_max (optimal minimum temperature/optimal maximum temperature)
- 25-30°C: Consistent in almost all Japanese and English gardening materials [1][2][3][4][5][6].
base_temperature (base temperature)
- 15°C: Many sources specify a "minimum of 15°C", below which germination is significantly delayed or stopped [1][2][3][7].
low_stress_threshold (low temperature stress threshold)
- Although there is no clear numerical definition in the literature, it has been reported that germination delays and deterioration of alignment occur at temperatures below 20°C (especially 15°C to 20°C) [3][4][7].
high_stress_threshold (high-temperature stress threshold)
- Decreased germination rate and poor alignment are observed above 30°C, but significant negative effects are observed at 35-40°C [2][3].
max_temperature (maximum allowable temperature)
- 40°C: Often indicated as the "maximum temperature at which germination is possible", but in reality, exceeding 30°C has a negative effect on germination rate and uniformity [3][7].
frost_threshold (frost damage threshold)
- There is no clearly quantified information, and almost all documents state that "sowing should be done after late frost has completely disappeared," and frost (below 0°C) is fatal to seeds and new leaves [5][6][8].
sterility_risk_threshold (sterility risk threshold)
- Not applicable during germination period.

Multiple definitions and ranges

Temperature ranges that are consistent in almost all literature and practice books. There is no exact numerical value for the stress threshold, so in practice it is understood that it is dangerous when the temperature deviates from the optimum temperature.

Reference

"Suitable temperature for germination: 25-30°C (minimum 15°C - maximum 40°C)" [1]
"In home gardens, sow after the risk of late frost has passed" [8]

2. Temperature requirements during the seedling stage

Seedling stage parameter organization

optimal_min/optimal_max (optimal minimum temperature/optimal maximum temperature)
- 20-25°C (Takii seedlings, hydroponic cultivation guide, etc.) [9][10]
- 25-32°C (daytime), 14-16 °C (nighttime): Miyagi Prefecture Vegetable Production Manual [10]
base_temperature (reference temperature)
- There are few clear reference temperatures in the literature, and 14 to 16°C (nighttime) is often considered the "minimum optimum temperature," but there are few absolute lower limit values specified [10].
low_stress_threshold (low_stress_threshold)
- 8°C: Physiological low-temperature stress (particularly suppression of nutrient uptake) has been reported, but stress begins below the minimum night temperature of 14-16°C in agricultural fields [12][13].
high_stress_threshold (high temperature stress threshold)
- Over 33°C: If the morning peak in the greenhouse exceeds 30-33°C, vine elongation will be suppressed and quality will deteriorate [11].
max_temperature (maximum allowable temperature)
- About 45°C: Physiological damage occurs to leaves and growing bodies [14].
frost_threshold (frost damage threshold)
- Although there is no clear numerical value in Japanese literature, in practice seedlings will be fatally damaged at temperatures below around 0°C [5][6].
sterility_risk_threshold (sterility risk threshold)
- Not applicable at seedling stage.

Ambiguous parameter

base_temperature, low_stress_threshold, frost_threshold There are no Japanese materials that clearly quantify this, and farmers' practice books include statements such as ``Avoiding minimum night temperatures below 14-16°C'' and ``Planting after the risk of frost has passed.'' class="header-anchor" href="#Flowering period parameter arrangement" aria-label="Permalink to "Organization of flowering period parameters">

optimal_min/optimal_max (optimal minimum temperature/optimal maximum temperature)
- 22-28°C during the day, 25-28°C in the morning, 17-25°C at night [15][16][17][18][19]
- Some literature suggests a range of 24-30°C or 20-28°C [16][20].
base_temperature (base temperature)
- 10-12°C (lower limit of growth) [17][19]
- 15°C (minimum practical temperature, especially for flower differentiation and fruit set safety) [17][18]
low_stress_threshold (low temperature stress threshold)
- Below 10-15°C: Suppression of growth and flowering, decrease in fertility and pollen activity, described with a range rather than a clear numerical value [18][21][22].
high_stress_threshold (high temperature stress threshold)
- Over 35°C: Multiple sources point out the risk of poor anther cracking and reduced fertility due to high temperatures [22][23][24].
max_temperature (maximum allowable temperature)
- 35-40°C: Exceeding will cause poor fruit set and growth [17][22][23][24].
frost_threshold (frost damage threshold)
- −2 to 0°C: This range is considered fatal in almost all documents [17][19].
sterility_risk_threshold (sterility risk threshold)
- 35°C or higher (high temperature): poor fruit set, poor anther cracking, decreased pollen adhesion, etc.[22][23][24]
- Below 10-12°C (low temperature): Although there are few clear experimental values, adverse effects are mentioned [21][24].

Variation in range/definition

The stated temperature varies slightly depending on the practical manual, variety characteristics, and facility cultivation.
With regard to the temperature range for fertility and sterility, it is widely agreed that ``a high temperature of 35°C or higher is dangerous.'' On the other hand, on the low-temperature side, the danger increases below 12 to 15°C, but exact experimental values have not been specified.

4. Temperature requirements for the fruiting stage (fruit enlargement/harvesting stage)

Organization of fruiting period parameters

optimal_min/optimal_max (optimal minimum temperature/optimal maximum temperature)
- Ensure stable quality and yield at 20 to 30°C during the day [25][26][27][28][29].
- Many Japanese documents indicate that operating at 25-28°C in the morning, 20-25°C in the afternoon, and 15-16°C at night is suitable for fruit fattening [26][27].
- Soil temperature of 18-23°C is also required [25][26].
base_temperature
- 15-16°C (growth/fruit enlargement stop line) [25][30].
- 15.5°C (60℉) on Growing Degree Days based on overseas crop models [30].
low_stress_threshold (low-temperature stress threshold)
- Poor fruit set and chill failure begin at temperatures below 15°C or between 9 and 14°C [25][28][31].
high_stress_threshold (high temperature stress threshold)
- Abnormal shape, increased respiration, and decreased commercial value at temperatures above 30-33°C [26][29].
- Significant quality defects and yield decreases at 38-40°C [26][32][33][34].
max_temperature (maximum allowable temperature)
- 35-38°C. Exceeding this will cause permanent damage and rapid fruit failure [26][34].
- Growth suppression and reproductive organ dysfunction occur at temperatures above 42°C [33][34].
frost_threshold
- Around 0°C. Fatal freezing damage below -2°C. Common to fruits, seedlings, and growing individuals [17][19][27].
- Long-term management at 7-10°C increases storage "chill damage" (especially after harvest) [30][35].
sterility_risk_threshold (sterility risk threshold)
- Not directly applicable to fruiting period.

Range or contradiction

Some documents show different values depending on traits, cultivation forms, and soil conditions, but most documents agree that productivity drops significantly when temperatures exceed 33 to 38°C.
On the low-temperature side, the importance of soil temperature is sometimes emphasized over air temperature alone [25].

5. Temperature parameters of each stage Summary table

Stage	optimal_min (°C)	optimal_max (°C)	base_temperature (°C)	low_stress_threshold (°C)	high_stress_threshold (°C)	max_temperat ure(°C)	frost_threshold(°C)	sterility_risk_threshold(°C)
Germination period	25	30	15	15 to less than 20	30 or more (35 to 40)	40	0 Below (need to be avoided)	Not applicable
Seedling stage	20	25-32	14-16 Estimated	Less than 14-16 (strong stress below 8)	33 or above	45 Leaf damage (literature)	0 or less (estimated)	Not applicable
Flowering period	22 (night 17)	28 (night 25)	10 to 15	10 to less than 15	35 to 40	35 to 40	−2 to 0	35 or more/10 to 12 Less than (estimated)
Fruiting period	20 (night 15-16)	30	15-16	Less than 15 (chill failure at 9-14)	30-33-38< /td>	38～42	0, −2	Not applicable

*There is a slight difference of about ±2°C between scientific and horticultural materials, but it generally converges within the above range.

6. Parameters without a clear definition/Ambiguous

low_stress_threshold/high_stress_threshold
- Many documents do not specify clear numerical values, and explain that ``deviating from the optimal range causes stress and poor growth.''
- There is an experimental value of 8°C for low temperature stress during the seedling stage, but in practice, the risk level is below 14-16°C.
- On the high-temperature side, there are many practical reports that damage is significant when the temperature exceeds 33-35°C.
sterility_risk_threshold (flowering period)
- On the high temperature side, almost all documents agree that 35°C or higher is a dangerous range. There is no clear specification on the low temperature side, and although it is usually mentioned that pollen fertility decreases at temperatures below 12-15°C, numerical experimental values are scarce.
frost_threshold
- 0°C to -2°C is considered fatal at all stages, but depending on the literature, it may only be expressed as ``Be careful of frost damage.''

7. Practical points of temperature management

Seeding/planting: Be sure to avoid late frost and ensure a minimum soil temperature and night temperature of 15°C [5][6].
Seedling cultivation: Controlled at 20-25°C. Growth is suppressed at night temperatures below 14-16°C, so avoidance of low temperatures is essential [10].
Flowering and fruiting: Maintain a temperature of 25-28°C during the day and 18-25°C at night, and avoid temperatures above 35°C and below 12°C [16][17][22][24].
Fruit enlargement/harvesting: Both soil temperature and air temperature should be controlled at 15°C to 30°C. If it exceeds 30°C, an increase in abnormal fruit and a decrease in yield will occur [25][27][29].
High/low temperature stress: Physiological/yield failure occurs at 33-38°C and 9-14°C. -2 to 0°C is lethal [16][19][22][32].

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Detailed summary of temperature requirements at each growth stage of cucumber (cucumber) ​

Overview ​

1. Temperature requirements for germination period ​

Organization of germination period parameters ​

Multiple definitions and ranges ​

Reference ​

2. Temperature requirements during the seedling stage ​

Seedling stage parameter organization ​

Ambiguous parameter ​

Variation in range/definition ​

4. Temperature requirements for the fruiting stage (fruit enlargement/harvesting stage) ​

Organization of fruiting period parameters ​

Range or contradiction ​

5. Temperature parameters of each stage Summary table ​

6. Parameters without a clear definition/Ambiguous ​

7. Practical points of temperature management ​

Sources ​