Edible Gardening

Prevent Blossom-End Rot

blossom end rot

Growing tomatoes in the South is a difficult endeavor. Tomatoes are relatively easy to grow, but there can be many disease problems in the hot and humid Southeast. One disease that shows up every year is blossom-end rot, but it is very easy to prevent with some planning.

Blossom-end rot is a physiological disorder caused by a lack of calcium, not by a pathogen.  Fruit showing this disorder will develop a dry brown or tan decayed area on the end of the fruit not attached to the stem (aka the blossom end).  The decayed area appears small at first, but enlarges as the fruit grows.  This disorder occurs on the fruit of tomatoes, peppers, and eggplants.

Blossom-end rot often occurs when rapidly growing plants experience a period of drought.  The less water taken up by the plant, the less calcium is moved into the plant.  So sometimes, the soil will have plenty of calcium that is just not plant accessible.  In order to moderate the amount of moisture plants are receiving, mulch using straw, pine straw or newspaper.  Plastic and other mulches may also be used.  Be sure to irrigate when necessary; tomatoes require 1 – 1.5 inches of water per week, especially during fruiting.

To help prevent blossom-end rot, take a soil sample.  Soil sample kits are available through your local NC Cooperative Extension Center.  Testing is a free service offered through the NC Department of Agriculture.  Although soil samples can be taken at any time of the year, take a sample in the fall to have results ready by the next growing season.

The soil sample results will indicate the amount of lime and fertilizer to incorporate into your garden.  Both calcitic and dolomitic lime contains calcium and will correct the calcium deficiency in the soil if applied at the proper rate.  Lime will also adjust the acidity of the soil.  Apply lime 2-3 months prior to planting your garden since it takes time to make corrections.  Apply fertilizer as indicated on your results.  Applying too much at one time can also result in blossom-end rot.

What if you already have blossom-end rot on your tomato fruit?  Lime will take time to work.  Often the best solution is to pull off those tomatoes showing symptoms of blossom-end rot and water more regularly. Many times the plant grows out of the calcium deficiency.

Another solution is to use a calcium spray.  However, a foliar spray may not be necessary, again since the plant often grows out of the calcium deficiency.  A foliar spray containing calcium nitrate or calcium chloride works well if applied 2-3 times per week.  Be sure to read and follow the label instructions.

Blossom-end rot, although a common disorder, is easy to prevent.  A quick and easy (maybe dirty too!) soil sample will give you the precise information you need to make an ideal growing environment for your garden plants.  In addition, providing an adequate growing environment will provide plants with the resources needed to grow and fruit properly.

Featured photo / NC State Pathology Dept.


Stephanie Romelczyk is a Horticulture Agent.