1. Effects of high temperatures on blueberry growth: Blueberries can tolerate temperatures of 40–50°C during the growing season. When temperatures exceed 40–50°C, blueberries may experience growth and development issues due to difficulty in root water absorption. Dwarf blueberries produce more rhizomes and grow faster at 30°C. In lowbush blueberry-growing regions, low summer temperatures are the primary limiting factor for blueberry growth and development. When soil temperature increases from 13°C to 32°C, the growth rate of highbush blueberries increases proportionally.
Low temperatures limit photosynthesis in blueberry leaves, and early spring cold temperatures are detrimental to plant growth. In the Changbai Mountain region, after blueberry leaves unfurl, if they are exposed to frost damage, the leaves do not fall off but turn an abnormal red color, thereby impairing photosynthesis. Once the leaves turn red, it takes approximately one month for them to turn green again as temperatures rise. Temperature also affects flower bud formation and fruit development. The number of flower buds formed by lowbush blueberries at 25.6°C is significantly higher than those formed at 15.6°C. Therefore, low temperatures during the growing season are one of the factors causing severe yield reductions in lowbush blueberries the following year. The fruit set rate of highbush blueberries is nearly twice as high at 16–27°C compared to 8–24°C, and under high temperatures, fruit development is rapid, resulting in larger fruit size and an average maturation period 2–5 days earlier than under low-temperature conditions.
Different blueberry varieties have their own suitable climatic conditions. Northern highbush blueberries are suitable for cultivation in northern regions with slightly longer dormancy periods; southern highbush blueberries are suitable for cultivation in southern regions with shorter low-temperature dormancy periods; semi-highbush blueberries are suitable for cultivation in northern regions with longer dormancy periods and colder climates; lowbush blueberries have strong drought and cold tolerance and are suitable for cultivation in cold northern regions; rabbit-eye blueberries are drought-tolerant, heat-tolerant, have shorter dormancy and water-requirement periods, and are suitable for cultivation in southern regions.
2. The impact of low temperatures on blueberry growth: Blueberries’ tolerance to low temperatures largely depends on the extent of cold acclimatization before exposure to low temperatures. Under field conditions, branches of the Early Blue variety suffered freeze damage and died at -20°C, while the same variety showed no freeze damage even at -40°C the following year. This difference is attributed to variations in cold acclimatization levels between years.
Although blueberries have strong cold tolerance, frost damage frequently occurs. The occurrence and severity of frost damage depend on the intensity and duration of winter low temperatures, as well as the timing of their onset. The woody stems of highbush blueberries take a longer time to lignify, reaching maximum lignification by the end of January. Lignification occurs most rapidly in September and October, and the low temperatures in September and October make highbush blueberries more susceptible to frost damage than in January. In addition to temperature, other factors such as moisture content are also important contributors to winter frost damage in blueberries. For example, increasing moisture content within buds reduces cold tolerance, while reducing moisture content enhances cold tolerance.
The cold tolerance of blueberry flower buds is an important factor influencing blueberry production. The cold tolerance of flower buds is related to various factors, such as photoperiod, temperature, bud size, color, and moisture content. Generally, buds that are plump, have low moisture content, and high anthocyanin content exhibit strong cold tolerance, while those with the opposite characteristics have poor cold tolerance. Under field conditions, if buds naturally lose moisture slowly, cold tolerance can be enhanced. For example, the flower buds of cold-tolerant hybrid varieties of highbush blueberries can withstand temperatures as low as -40°C.
Different blueberry varieties exhibit varying levels of cold tolerance. Dwarf blueberries are the most cold-tolerant, followed by highbush blueberries, while rabbiteye blueberries have the lowest cold tolerance. In mid-January, highbush blueberry branches suffered frost damage at -34°C, and buds were damaged at -29°C. At -26°C, rabbiteye blueberry flower buds died, while highbush blueberries showed no frost damage. Within the same species, different varieties also exhibit varying levels of cold tolerance. Among highbush blueberries, the Bluebell and Blue Line varieties are highly cold-tolerant, while among semi-highbush blueberries, the Northland, North Blue, and North Sky varieties are relatively cold-tolerant. In addition to their inherent cold tolerance, another important factor for lowbush blueberry varieties is their compact growth habit, which allows winter snow to completely cover them when cultivated in northern regions, ensuring safe overwintering.
Post time: Aug-19-2025