WSU Extension


Tomato : Blossom-end rot
(revision date: 9/21/2015)

Blossom end rot is a physiological problem affecting tomato fruit. A tan, water-soaked lesion develops near the blossom scar on the end of the fruit. The lesion enlarges, turns black and leathery, and can eventually involve up to 1/3 or more of the fruit. Affected tomatoes are flattened or concave on the blossom end. Occasionally, blossom end rot may occur on the side of the fruit or may cause discoloration of the internal tissues without external symptoms. Blossom end rot is caused by insufficient calcium in the end of the fruit. Inconsistent soil moisture and high temperatures are often factors involved in this problem. It can be caused by several factors including drought, overwatering, root damage, insufficient soil calcium levels, or high concentrations of salts in the soil. Varieties differ greatly in their susceptibility to this problem.
Management Options

Non-Chemical Management
  • Select cultivars that have low susceptibility to blossom-end rot such as Celebrity, Jet Star, and Mountain Pride, and avoid cultivars with high susceptibility like Big Boy, and Wonder Boy.
  • Trellising and pruning can increase blossom end rot by increasing plant stress.
  • Plant in well-drained soils and water consistently.
  • Provide proper culture. Fertilize moderately to avoid buildup of salts in the soil and to prevent excessive growth which may decrease calcium availability to fruits. Mulching plants may be helpful.
  • Soil testing may be necessary to determine calcium levels. Your county extension agent or WSU Master Gardeners can recommend soil testing laboratories in your area.
  • Calcium-deficient soils can be corrected with use of lime or dolomitic lime in the fall or 2-4 months before planting.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

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Caption: Tomato blossom-end rot
Photo by: R.S. Byther
Caption: Blossom end rot
Photo by: F. Buajaila