Some problems with tomatoes are not caused by insects or diseases. Here's a few sommon problems.
Blossom End Rot
This rot begins on the bottom -- or blossom -- end of the tomato as a sunken, water-soaked spot. The spot turns brown or black, dry and leathery as it grows larger. It affects both green and ripe tomatoes and is caused by a lack of calcium in the plant, which is usually the result of a fluctuating moisture supply.
Staked or pruned plants, or plum-shaped fruits are more likely to suffer from blossom end rot than are unstaked tomatoes. The rot often starts if the plants are in the midst of a growth spurt and they're suddenly hit by a hot, dry spell. The moisture stress brings on the problem.
Prevention is the best cure. Concentrate on keeping the water supply even throughout the season. Mulch can be a big help. It conserves soil moisture and keeps down weeds. Cultivating deeper than about an inch within a foot of the plants may damage roots and encourage rot.
One on-the-spot measure for gardeners facing a blossom end rot crisis: Apply calcium right away to the leaves. You can get the calcium in the form of calcium chloride -- sold by some seed companies and by hardware stores in northern areas as de-icing salt. Mix one tablespoon to a gallon of water and spray two or three times a week. This will help some.
Tomatoes often start to crack during warm, rainy periods -- especially if this weather comes after a dry spell. The tomatoes simply expand too fast. They're most likely to crack when they've reached full size and are beginning to turn color. Some varieties are resistant to cracking, such as 'Early Girl' and 'Jet Star'. Again, the best way to avoid the problem is to keep the moisture supply as steady as possible throughout the season and to select crack-resistant varieties.
This is another kind of cracking or scarring. Tomatoes develop unusual swelling and streaks of scar tissue. Catfacing isn't a disease; it's caused by abnormal development of the tomato flower at blossom time. Cool weather may cause the flower problems and older varieties seem to be more susceptible than newer ones.
Some years many of the early-season blooms simply fall off without setting fruit. This is the result of cool night temperatures (below 55° F). Some varieties, such as 'Pixie II', will keep their blossoms and set fruit in cool weather. Blossom drop also occurs when day temperatures are consistently above 90° F or night temperatures remain above 75° F in the summer. This is one reason why it can be difficult to get a summer-long crop of tomatoes in the hot sections of the South and Southwest. Certain varieties, such as 'Heatwave', will set fruits well even under hot, dry conditions.
Curling of Leaves
Curling or "leaf roll" is very common but doesn't harm production. It usually occurs after periods of heavy rains, when the soil is very wet. Older leaves are affected, rolling up until their edges touch. Some varieties are more prone to leaf roll than others. Plant in well-drained soil to minimize leaf roll.
This occurs when green or ripening tomatoes get too much exposure to the hot sun. At first, a yellowish white patch appears on the side of the tomato facing the sun. The area gets larger as the fruit ripens and becomes grayish white. To guard against sunscald, be careful not to overprune and don't remove foliage shading the fruits. Especially in hot climates, it may be a good idea to grow plants in cages where they'll develop lots of protective foliage. Control diseases such as early blight that cause plants to lose foliage.
Although these common problems make tomatoes look ugly, they're okay to eat fresh. Just cut away the affected part and enjoy the rest.
This article is a part of our Vegetable Gardening Guide for Tomatoes / Care.