Gardening Articles: Care :: Pests & Problems

When Good Tomatoes Go Bad

by Charlie Nardozzi

Growth cracks on tomatoes can lead to serious deterioration of the fruit.
Finally, it's time to enjoy the results of weeks of pampering young tomato plants. However, nothing is more frustrating after so much effort than seeing misshapen or rotten fruits on the vines. It's easy to blame pests or diseases, but the weather, the tomato variety, or even your gardening practices may be the actual cause.

To help you identify what's spoiling your tomatoes, we've compiled a list of eight of the most common tomato fruit problems not caused by insect or disease. You can do something about most of these problems now, so the next cluster of tomatoes on your plants could be perfect. We also include suggestions for resistant varieties to plant next year.

But first, here are the three basic steps for growing healthy, perfect tomatoes:

Supply and conserve water. Tomato plants need 1 to 1 1/2 inches of water a week from either rain or irrigation. Often the problem is not the amount of water, but sudden changes in soil-moisture levels. To conserve moisture, mulch plants with a 4- to 6-inch layer of hay or straw.

Keep plants warm, but not hot. In early summer, protect young plants from cold temperatures by covering them, especially at night. Conversely, in mid- to late summer, protect plants (especially fruits) from high temperatures with afternoon shade.

Feed carefully and avoid high-nitrogen fertilizers. Two weeks before planting, work in a 2- to 3-inch layer of compost, then fertilize the plants with a complete fertilizer (5-10-10) at the rates recommended on the label. Side-dress your tomatoes monthly with a complete fertilizer.

Eight Avoidable Tomato Problems

These stresses have sent many befuddled gardeners looking for a pest or disease. Tomato experts call the stresses physiological problems, meaning the cause has to do with the functioning of the plant itself, not with any outside agent.

Blossom-End Rot

What it looks like: Brown-black sunken areas appear on the blossom end of green or ripening fruit.

Causes: Insufficient calcium levels in the developing fruit cause the cells in the blossom end to break down. Though insufficient levels of calcium in the soil may be the cause, it is more likely fluctuating moisture levels. This is why it is important to apply a mulch. Water transports calcium through the plant. With insufficient water, calcium doesn't move quickly enough to the fruits. As little as 30 minutes of water deficiency at any time can cause blossom-end rot.

These other factors contribute but are all ultimately connected to calcium availability in the developing fruit: excess nitrogen fertilization, high soil salinity, waterlogged soils, root damage during cultivation, and soil pH that's too low or too high. Blossom-end rot occurs most often on the first fruit clusters, when the plant grows quickly and demands calcium for leaf growth.

What to do: Pick and destroy rotten fruits, keep the soil pH around 6.5, reduce nitrogen fertilization, and apply a complete fertilizer such as 5-10-10 (1/2 cup per 10-foot row) once early in the growing season. Also, mulch early in the season with a 4- to 6-inch layer of hay or straw. Apply at least 1 1/2 inches of water a week, and avoid growing susceptible older indeterminates (vining tomatoes) such as 'Beefsteak' and both determinate and indeterminate varieties of plum tomatoes ('Roma' is one example).
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