This is an archived article that was published on sltrib.com in 2007, and information in the article may be outdated. It is provided only for personal research purposes and may not be reprinted.

Tasty homegrown tomatoes often don't look as perfect as those in grocery stores.

Weather and soil conditions cause many developmental defects, including cracking, zippering and blossom-end rot. While there is no quick cure for these defects, soil amendments and careful note-keeping may help guide you toward avoiding these problems in the future.

Cracking: When tomato flesh and gel locules grow or take up water too quickly, the tomatoes crack. Cracks are tears in the skin that leave the flesh exposed. Concentric cracks form when skin splits around the stem, usually at or above the tomato shoulder. Damage is shallow and the flesh under these cracks usually dries and heals quickly, preventing rot. Although concentric cracks are obvious imperfections, they rarely affect the flavor or edibility of the tomato.

Radial cracks are splits in the tomato fruit. Starting at a weak point where tomato skin joins the stem, radial cracks open downward toward the blossom end of the fruit. Radial cracks can be avoided by carefully managing soil moisture. Sustain good soil structure with regular additions of compost or other organic-matter amendments.

Zippering and catface: Zipper scars are caused when flower parts stick to newly developing fruit. Zippering may be unavoidable since the cause is usually weather-related, but some cultivars are more susceptible than others to zippering. These scars are rarely bad enough to affect fruit edibility.

Catfacing is also caused by sticky flower parts that fail to separate from developing fruit. Damage is more extensive than zippering; the fruit may be so deformed that it cannot mature and ripen.

Blossom-end rot (BER): This defect is a physiological weakness in tomato fruit near the blossom end. BER results from a calcium deficiency in the fruit, even though Utah's native soil is loaded with calcium. Many gardeners tout potions and cures for BER, and these myths are perpetuated when post-potion pickings show far less BER. Tomato fruit set in early spring often have BER while fruit developing one or two weeks later are usually fine. Any condition or event that slows or prevents water movement from roots through leaves can also lead to BER. Transplant shock, cool and cloudy weather and drought stress are all to blame.

BER may weaken the tomato fruit tissue enough so that bacteria and fungi may enter and infect the fruit, causing rotten tomatoes. Some varieties are less susceptible than others to BER.

Sunscald: Young fruit exposed to intense sunlight may develop sunscald, patches of dead tissue that look bleached and wrinkly. Avoid sunscald by supporting tomato vines with cages or staking so that fruit is shaded by the plant canopy.

To learn about more tomato problems and how to solve them, visit the Utah State University Extension publication Web site, at extension.usu.edu/htm/publications, and you can find the fact sheet "Tomatoes in the Garden" at extension.usu.edu/files/publications/factsheet/HG 2004-05.pdf.

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MAGGIE WOLF is an assistant professor for Utah State University Extension in Salt Lake County. E-mail her at maggiew@ext.usu.edu.