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Gardening Articles: Edibles :: Vegetables

When Good Tomatoes Go Bad (page 2 of 3)

by Charlie Nardozzi

Blotchy Ripening (graywall)

What it looks like: First you see light green or clear blotches on green fruit. These patches gradually turn yellow, and the tomato doesn't ripen evenly. Often, the tomato is rotten inside.

Causes: Graywall is most often caused by shade and cool temperatures followed by bright, sunny weather. Excessive foliage growth also causes it, so the most vigorous indeterminate tomato varieties are the most susceptible. But other factors promote graywall. For instance, it occurs more often in plants growing in soggy soils, and diseases like tobacco mosaic virus may indirectly cause this condition.

What to do: Grow determinate bush varieties that allow sunlight through the leaf canopy. Decrease nitrogen fertilizer, and increase potassium. Stake or cage plants to allow sufficient light to reach the fruit.


What it looks like: Misshapen fruit has black scarred areas on the blossom end that often rot.

Causes: Catfacing happens when flowers don't develop properly. The most common cause is low temperatures (below 65° F during the day and 55° F at night) three weeks before flowers open. High wind on plants with little foliage can also damage blossoms. Although a common problem on the first fruit clusters, it disappears when temperatures rise. But it may recur if the plants are still setting fruit as temperatures drop in the autumn. Larger and older varieties such as 'Beefsteak' are more susceptible to catfacing.

What to do: Grow the plants when temperatures are high during pollination by planting later in the season and protecting transplants from cold and wind with plastic cloches or floating row covers.

What to do: To avoid catfacing next year, grow modern hybrid varieties that are much less likely than older ones to be bothered by low temperatures and don't prune off the foliage.

Fruit Cracks

What it looks like: When ripening, fruits crack around the stem end and along the sides, and the fruit rots. Cracks may be radial or concentric.

Causes: Abruptly alternating wet and dry periods cause cracking. When the plant takes up deep drinks of moisture after a dry spell, the fruit cells expand too fast and burst, and the skin cracks. (Heavy dew worsens cracking because the fruit can take water in through the skin.) The soft-fruited 'Celebrity' and cherry tomato 'Sweet 100' are particularly prone to cracking. Too much nitrogen in the soil also contributes to the problem. Green fruits usually don't crack because they're harder and can't expand as fast, and their skin cells are stronger.

What to do: Keep the soil evenly moist, especially during ripening, with a 4- to 6-inch mulch of hay or straw. Don't overfertilize. If maintaining soil moisture is difficult in your area, plant less-susceptible varieties next year. 'Mountain Spring' and 'Mountain Belle' (a cherry tomato) are good options.
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