Mater gone bad: Proper mulching and watering and avoiding disruption of the plant’s roots can help prevent blossom-end rot. Photo by Darrell Blackwelder, for the Salisbury Post.

rotten: Too much fertilizer, too little calcium are among the causes of blossom-end rot in tomatoes. Photo by Darrell Blackwelder, for the Salisbury Post.

By Darrell Blackwelder

Salisbury Post

Erratic weather patterns have caused many problems this season, especially with tomatoes.

Unseasonal weather this spring and now summer often affects the growth and development of vegetables, especially tomatoes. The most common problem this summer is blossom-end rot.

There are a number of reasons why this problem occurs. The most common is lack of calcium. Gardens that have not been limed in the past two to three years need about 2 cups of lime for each plant. Make sure to work the lime into the soil 12 inches deep. However, it is best to take a soil sample to determine the correct amount.

Soil sample boxes are available from the Cooperative Extension office and should be directly mailed to the N.C. Department of Agriculture by the home gardener.

Also, too much fertilizer at one time can result in blossom-end rot, especially high nitrogen fertilizers. Light applications of fertilizers with phosphate are beneficial. Following soil test recommendations is the best way to insure proper fertilization.

Calcium chloride sprays also aid in the control of this physiological problem. These can be applied as a fertilizer supplement. Follow label instructions carefully.

Lack of water when the tomato plant is setting fruit causes some fruit to have blossom-end rot. This condition occurs not only in tomatoes, but also in squash and watermelons. Blossom-end rot is a calcium deficiency sparked by periods of drought or, in some instances, too much water. Plants must be irrigated on a regular basis to prevent blossom-end rot.

Tomato plants require about 1.5 inches of water per week during fruiting. This amount of water should be supplied by rain or irrigation. Extreme fluctuations in soil moisture results in a greater incidence of blossom-end rot.

Vegetable specialists from N.C. State University have proven that fruit laden plants may use up to a gallon of water a day during peak growth.

Mulching tomatoes and other vegetables with straw, pine straw, decomposed sawdust, ground decomposed corn cobs, plastic or newspapers will conserve moisture and reduce blossom-end rot.

Avoid tilling or hoeing around fruit-bearing tomato plants. Any disturbance of tender roots disrupts the flow of water and nutrients and exacerbates the problem.

Also, some tomato varieties are more predisposed to blossom-end rot than others. It's always a good practice to plant different varieties for this reason. Commercial tomato producers always try new varieties to determine growth habits during varying conditions.

Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County; call 704-216-8970.

Web sites:

http://rowan.ces.ncsu.edu

http://www.rowanmastergardener.com

http://www.rowanhorticulture.com

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