Gardening Articles: Care :: Pests & Problems
When Good Tomatoes Go Bad (page 3 of 3)
by Charlie Nardozzi
Green (or yellow) Shoulders
Cause: Normally chlorophyll breaks down as the fruit ripens. However, in some varieties, during periods of high temperatures and direct sun exposure, the chlorophyll does not break down, or does so too slowly.
What to do: This problem is most common in heirloom varieties that happen to lack the gene for uniform ripening. Most modern hybrids have this gene and rarely develop green shoulders. However, if you want to grow the older, susceptible varieties, minimize green shoulders by maintaining good foliage cover and picking the tomatoes when they're entirely green to ripen indoors, away from exposure to direct sun.
Causes: Puffiness is caused by incomplete pollination, which in turn is most commonly caused by temperatures that are too high or too low. (Tomatoes are almost completely self-pollinating, so pollinating insects aren't a factor.) Whenever nighttime temperatures drop below 55° F or daytime temperatures rise above 100° F, seed doesn't set properly. Improper pollination prevents the jelly of the inside fruit chamber from developing. Also, too much nitrogen or too little potassium in the soil causes poor pollen formation, leading to puffiness.
What to do: Set plants out once nighttime temperatures are consistently above 55° F, or protect young transplants from cold with a floating row cover. In hot climates, use shadecloth to keep plants cool. Protect them from hot winds. Reduce nitrogen fertilization, and test soil to check potassium levels. Next year, plant resistant varieties, such as 'Celebrity' and 'Better Boy', which are less likely to develop the problem under any circumstances.
Cause: This discoloration is like a sunburn. Fruits exposed either suddenly or continually to hot sun develop sunscald, which is most likely to occur on varieties that don't produce enough leaves.
What to do: Avoid pruning leaves or stems while the fruit is ripening, and consider shading the fruit. A small section of shadecloth or row cover would suffice. Finally, try to reduce the severity of leaf diseases such as early and late blight, common fungal diseases. If you live where summers are sunny and hot, grow indeterminate varieties that produce a thick cover of shading leaves. Examples are 'Jet Star', and 'Big Beef'.
Cause: Temperatures below 55° F when flowers are dropping off the young fruit cause this condition. Zippering can occur at higher temperatures, too. Some varieties, such as 'Mountain Spring' and 'Mountain Pride', are genetically predisposed to the problem. Others, such as 'Big Beef', are not.
What to do: Cover young transplants with floating row covers to reduce the chances of cold damage to young fruit. Next year, plant a resistant variety such as 'Big Beef'.
Charlie Nardozzi is a senior horticulturist at National Gardening.
Photo courtesy of University of Wisconsin-Madison, Dept. of Plant Pathology