Stupid tomato tricks: Why isn’t my fruit cute?

Several physiological problems can ruin the appearance of tomatoes.

In the big, wide world of plants, there can be insect problems, disease problems and a really big category called physiological problems. These occur because of weather or human management problems. Sometimes, they are referred to as abiotic problems because they are not caused by anything living.

Tomatoes have their share of fruit problems. As with everything else, those problems can be caused by weather or human mismanagement or a combination of the two. Portions of some tomatoes may still be edible. But if you are selling the fruit, the customers will shy away.

The problems listed are caused by high temperatures, no rainfall, uneven watering or too much sun. This 2012 drought season can be summed up as: too hot, too sunny and too dry.

Blossom end rot

Blossom end rot
Blossom end rot. Photo credit: David B. Langston, Univ. of GA, Bugwood.org

The fruit is normal on the stem end but the bottom or blossom end is flat, leathery and black or brown. This is the most common tomato disorder. The technical reason is that there is not enough calcium in the soil. The real reason is that there is not enough water to push the dissolved calcium through the roots, up the stem and into the end of the fruit. Often when a plant begins making fruit, there will a couple of “tomato mistakes.” This problem corrects itself. But if many fruit are affected, it can also be caused by too big of a root system in too small of a container or raised bed. Consistent, deep moisture is the key.

Growth cracks

Concentric growth rings
Concentric growth rings. Photo credit: Paul Bachi, Univ of KY, Bugwood.org

There are either dark, concentric rings around the stem end of the fruit or radial cracks making a star pattern with the stem being the middle of the star. Growth cracks appear when the tomato plant is dry and receives a sudden, overabundance of rain or irrigation. The fruit expands rapidly and, simply, rips its pants. The splits are near the stem and often heal to a dark scar.

Yellow shoulder

yellow shoulder
Yellow shoulder. Photo credit:
Paul Bachi, Univ of KY, Bugwood.org

The top of the fruit around the stem is called the shoulder of the tomato. This area is yellow and more firm than the rest of the red fruit. It is caused by high temperatures during the ripening season. This is common in tomato varieties that have dark green shoulders when the fruit is unripe and green.

Sun scald

Sun scald
Sun scald. Photo credit:
Howard F. Schwartz, Col St Univ, Bugwood.org

With sun scald, a white and blistered area on top of the tomato fruit turns white and eventually becomes sunken on the side facing the sun. Decay may follow. This is caused by an overexposure to the sun and can be caused by pruning the plants or premature leaf drop.

White core

The inside of the fruit has white, firm or hard areas near the stem end that do not look like the rest of the tomato. Nothing is visible from the outside. This can be caused by high temperatures when ripening and, possibly the variety of tomato may be more sensitive. This is not the same as finding a few tough fibers inside the fruit radiating away from the stem. On big tomatoes, these white structures keep the heavy fruit from falling off because of the weight.

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