Plants Affected

• Blossom end rot affects tomatoes, eggplant and peppers, all of which are members of the nightshade family of plants. The condition generally will impact all the fruit on one plant, but it is not transmissible to other plants, no matter how closely together in the hydroponic setup they are growing. It is possible for the affected plants to have secondary fungal problems. If conditions are right, this fungus may spread to nearby plants.
  
  

Identification

• Fruits affected by blossom end rot will appear to be sunken in on the blossom, or bottom, end of the fruit. The area will take on a dry, brown, leathery appearance. If the fruit is cut open, that end of it will be brown and withered on the inside as well as the outside. If a secondary organism of any sort has taken hold, the area may appear black instead of brown, possibly with a moldy, fuzzy look to it. The entire fruit will be ruined.
  
  

Causes

• The main cause of blossom end rot is a calcium deficiency in the plants. Not enough calcium reaches the developing fruit, and the end rot sets in. Many hydroponic growers don't realize that their plants may be susceptible to this condition, since the plants are given an ongoing supply of well-balanced nutrients, but end rot is thought to be caused by a genetic problem that prevents the plant from being able to take in enough calcium as the fruit develops. Over-fertilization, which can happen when the nutrient solution is too strong, can also result in blossom end rot. In this case, the plants grow too rapidly to be able to transport the necessary calcium quickly enough, and end rot is the result.
  
  

Prevention

• One of the most important ways to prevent blossom end rot in hydroponic plants is to use plants that are resistant to this problem, thus virtually eliminating the genetic component. The hydroponic nutrient solution should be mixed according to directions and never made too strong. Solution should be changed completely every two weeks, and if the plants are using a lot of the liquid, it should be replaced every week. When nutrient tanks are topped off between changes, only fresh water should be used, since adding new nutrient solution to old solution results in an imbalance of nutrients and leads to blossom end rot and other problems. Spraying the green fruit directly with a calcium spray can also help in some cases.