There is little more satisfying than harvesting that first vine ripe tomato from the garden. And there is nothing more disappointing than having to throw it away because it is malformed with a dark patch on the blossom end.

Now that we are entering tomato harvest season, gardeners are starting to inspect their crop a bit more closely.

Unfortunately what they are finding is less than desirable. Here is what you can do to stop the rot and enjoy a bountiful tomato harvest this summer.

The brown leathery patch on the bottom, or blossom end, of the tomato fruit is called blossom-end rot. It is not caused by a disease and chemical sprays will not stop it. It is the result of a nutritional imbalance in the fruit  more specifically a calcium deficiency. Calcium is an important nutrient in the development of tomato fruit. Although there is usually an ample supply of calcium in garden soil, it is not always available for fruit development.

Warm spring temperatures cause rapid top growth with limited root growth. As the plant pulls calcium from the soil, it moves the nutrient in the water stream from roots to tops, bypassing the fruit and causing the deficiency. As the plant acclimates to summer weather, tops slow down and roots enlarge, bringing the plant back into balance.

Available calcium then can be used for fruit development. Blossom-end rot does not normally develop on later fruit.

The best way to stop blossom end rot is with water. Keep the soil uniformly moist throughout the growing season. Plants that have water are able to take up and move needed nutrients more easily. Next, do not overfertilize. Plants that are excessively lush because of overfertilization are usually more prone to developing blossom-end rot. Slow, sustained growth is better than fast, forced growth.

Finally be patient. Although the first fruit to set does not develop normally and are not very appetizing, eventually, the plant will work the problem out and you will harvest beautiful, full tomatoes.

 Bruce Chladny is horticulture agent at K-State Research and Extension-Douglas County. For more information, call him at 843-7058 from 8 a.m. to 5 p.m. weekdays.