Strawberry cultivation requires understanding temperature fluctuations throughout the growing season. While adaptable, specific temperature ranges are necessary for optimal growth, flowering, and fruit development. Managing temperature effectively is a primary consideration for gardeners aiming for a bountiful harvest. Understanding how strawberries react to cold and heat helps ensure plant health and productivity.
Optimal Temperatures for Strawberry Growth
Strawberries thrive in temperatures between 15 and 26°C (59-79°F) for overall plant growth. Daytime temperatures of 20-24°C (68-75°F) support photosynthesis and robust development. Nighttime temperatures of 10-12°C (50-54°F) increase fruit size, enhance flavor, and improve sweetness, contributing to the fruit’s sugar-acid balance.
For flowering, 16-20°C (60-68°F) is most favorable, with 15-18°C initiating flower production. Once fruit development begins, 15-16°C (59-61°F) is beneficial for maturation. Overall, the highest yields are observed when plants are grown within 18-23°C.
Strawberry Cold Tolerance and Winter Protection
Strawberry plants possess natural cold hardiness, entering dormancy triggered by shorter days and cooler temperatures, often indicated by the first frost. While dormant, they tolerate temperatures as low as -10°C (14°F) with adequate protection. However, the crown, containing developing flower buds for the next season, can be damaged or killed at -12°C to -14°C (7-10°F), and milder cold can reduce future yields. Unopened flower buds withstand temperatures down to 20°F (-6°C), but open blossoms are sensitive, suffering damage at 30°F (-1°C).
Sudden temperature drops below 20°F (-6°C) before plants harden off can cause severe injury. Repeated freezing and thawing cycles can cause “heaving,” pushing plants out of the soil and exposing roots to damage.
To protect strawberries, mulching with 2 to 3 inches of straw or chopped leaves is effective. Apply mulch after plants enter dormancy, typically when soil temperatures are consistently below 40°F or after a few nights below 20°F. In spring, remove mulch once soil temperatures reach about 40°F to allow new growth. For spring frost events, especially when flowers are present, floating row covers provide 2-10°F of temperature increase, or overhead irrigation can create a protective ice layer.
Strawberry Heat Tolerance and Summer Management
Strawberries experience stress when exposed to high temperatures, particularly those exceeding 28°C (82°F), which can induce thermal dormancy and cease flowering. Temperatures above 30°C (86°F) are detrimental, leading to wilting, reduced fruit set, and smaller fruit size. High heat also inhibits root growth and negatively affects fruit coloration and quality. Sunscald, appearing as bleached, leathery areas on fruit exposed to direct sunlight, is a common issue in hot conditions.
To manage strawberries during hot periods, consistent watering is crucial due to their shallow root systems. Increasing irrigation frequency, potentially twice daily when temperatures exceed 35°C (95°F), helps cool roots and meet high water demands. Providing shade, especially during the hottest parts of the day, is beneficial; using a 50-65% shade cloth or planting in areas with afternoon shade prevents heat stress and sunscald. Selecting heat-tolerant varieties like Albion, Sweet Charlie, Camarosa, Camino Real, or Chandler improves success in warmer climates. Avoid fertilizing during extreme heat, as plants absorb nutrients less efficiently, which can lead to salt buildup in the soil.