Blossom End Rot (BER) is a common physiological disorder affecting fruiting vegetables like tomatoes, peppers, eggplant, and squash. This condition is not caused by pests or pathogens, but by an imbalance in the plant’s nutrient uptake and water management. Addressing BER requires understanding its root cause and implementing both immediate corrections and long-term environmental strategies. Taking specific actions can stop the progression of BER and ensure a healthy harvest.
Recognizing Blossom End Rot
The first indication of Blossom End Rot is the appearance of a small, water-soaked spot on the bottom, or blossom end, of the developing fruit. This spot quickly enlarges, becoming dark brown or black, sunken, and distinctly leathery in texture. The affected area can eventually cover up to half of the fruit, making it inedible, although the fruit itself may continue to ripen prematurely.
The biological cause is a localized deficiency of calcium within the rapidly expanding fruit tissue. Calcium is an immobile element in the plant, meaning it cannot be redistributed from older leaves to the new, growing fruit. It is transported primarily through the xylem along with water via the process of transpiration.
The problem is usually not a lack of calcium in the soil itself, but rather the plant’s inability to transport it efficiently to the fruit. Fluctuations in soil moisture, such as alternating between dry and overly wet conditions, severely disrupt the steady flow of water and calcium. Factors like root damage, cold soils, or high concentrations of competing nutrients like potassium, magnesium, or ammonium-based nitrogen can also interfere with calcium uptake.
Immediate Fixes to Halt Progression
When Blossom End Rot is first observed, the affected fruit cannot be salvaged and should be removed immediately. Removing damaged fruit is an important first step because they continue to draw resources, including water and calcium, away from healthy, developing fruit. Disposing of the damaged produce allows the plant to redirect its limited resources to the remaining and subsequent fruit set.
The most effective immediate action is to stabilize the soil moisture, as inconsistent watering is the most frequent trigger for the disorder. Immediately provide deep watering to moisten the entire root zone, aiming for about one to one and a half inches of water per week, adjusting for weather. This consistent moisture promotes steady calcium uptake and transport through the plant’s vascular system.
Gardeners often turn to foliar calcium sprays for the currently developing fruit. While these sprays may offer a temporary boost, their effectiveness is limited because calcium is not easily redistributed within the plant’s internal tissues. If used, a calcium solution should be applied evenly to the leaves and young fruit in the evening to prevent sun scorch. This method is best viewed as a short-term measure, while the primary focus remains on correcting the soil moisture levels.
Strategies for Permanent Prevention
Long-term success relies on establishing a consistent environment that supports uninterrupted calcium delivery to the plant. The foundation of prevention is confirming the soil’s chemistry through a professional soil test. This test accurately determines the existing calcium levels and the soil’s pH, which dictates nutrient availability.
For most fruiting vegetables, the optimal soil pH range for calcium availability is slightly acidic to neutral, typically between 6.0 and 7.0. If the soil test indicates a low pH, amending the soil with dolomitic lime or calcitic lime before planting will raise the pH and supply slow-release calcium. If the pH is already correct but calcium is low, non-lime sources like gypsum can be incorporated, as this adds calcium without significantly altering the pH level.
Maintaining uniform soil moisture throughout the growing season is essential. Applying a two-to-three-inch layer of organic mulch, such as straw or shredded leaves, around the base of the plants helps prevent rapid evaporation and buffers the soil temperature. This practice ensures the plant has a continuous supply of water for transpiration, which is necessary to pull calcium into the fruit. Also, avoid excessive nitrogen fertilization, especially early in the season, as it promotes rapid leaf growth that competes with developing fruit for the available calcium.