ENVIRONMENTAL EFFECTS ON TOMATOES

Tomatoes like an even supply of water through the season--and if their water supply gets turned off and on all the time, they'll develop problems. I can't emphasize enough the need for an even water supply.

Like most other vegetables in the garden, tomatoes need at least 1 inch of rain or irrigation water per week for steady growth. In the hotter, dryer parts of the country, their needs go up to 2 inches of water per week during the summer months.

If you're curious about what an inch of water measures out to .... well, it's about 60 gallons for each 100 square feet of garden. So if you ever have to water by the bucket brigade, that's something to bear in mind.

There are many clever ways of watering tomatoes. One is to cut the top from some gallon-size cans, punch very small holes in the bottoms, and set them in the ground with only about 1 inch of the can showing above the surface. Use one can near (or between) each tomato plant and fill it two or three times per week--or more often if needed. When the plants start fruiting (fruits are the size of a quarter), add one or two teaspoons of a complete fertilizer, such as 5-10-10, to each can once a week for a sidedressing. You can use milk jugs in place of cans.

Always follow these watering guidelines:

Water thoroughly to encourage tomato roots to seek water and nutrients deep in the soil. With an extensive, deep root system plants hold up better in dry periods. When watering, soak the soil to a depth of at least 6 to 8 inches. A thorough soaking every 4 or 5 days on light, sandy soils and every 7 to 10 days on heavy soils is a good general guide for irrigating tomatoes in the absence of rain.

Water only when your plants need it. Tomatoes like moisture, but overwatering is harmful. Overwatering not only wastes water but also prevents the roots from getting air. If your plants look wilted on a hot summer afternoon, that's normal. They will usually perk up overnight. If plants are wilted in the morning, don't wait -- water them!

Watering early in the day reduces evaporation loss and allows plant foliage to dry quickly. Wet foliage overnight may help trigger some diseases. Furrow irrigation, drip irrigation, or soaker hoses deliver water right at the soil surface and not on the leaves, so you can water most anytime. Avoid watering at mid-day, because evaporation losses are highest at this time.

Use mulch to help retain moisture in the soil. Mulches reduce the fluctuation of soil moisture and that helps the crop enormously. But, remember, don't apply mulch until after the transplants have been going for 5 to 6 weeks. If mulch is applied too early, it will keep the soil cooler and plant growth will be slowed. However, when the soil is warm and plants have begun to grow, apply mulch and it will keep the soil cool during the summer and will also retain moisture.

Stop Blossom-End Rot

Too many fruits of tomato and bell pepper along with eggplant and watermelon grown in home gardens are lost each year to a condition called blossom-end rot. It is sad to see blossom rot erupt in a tomato row because you can't help the tomato once it's started. Blossom-end rot is a disorder found on the fruit near the blossom end and first appears as a darkened, sunken, leathery scar. This condition usually causes the fruit to ripen prematurely and makes it worthless.

Blossom-end rot can be caused by several factors and the severity of this condition can be compounded when two or more of these factors interact with each other. It is known that inadequate calcium levels in the fruit can cause this condition and a low soil calcium level, in combination with inadequate soil moisture, can compound the situation. Severely pruned tomato plants are more prone to develop blossom-end rot than unpruned plants. In order to control blossom-end rot, the home gardener will need to take several steps and one needs to start early, even before the crop is planted, if this condition is to be prevented.

1. Soil test early in the spring and apply dolomitic lime if needed. This should be done several weeks before planting.

2. In gardens where this condition has been severe in past seasons, also broadcast 5 lbs. of dolomitic lime per 100 square feet just before planting and plow the ground 6 to 8 inches deep.

3. Mulch plants with black plastic or organic mulch.

4. Apply irrigation water to keep soil uniformly moist throughout season.

5. A calcium spray, first applied when fruits are first visible can help prevent this disorder. Mix 4 tablespoons of calcium chloride per gallon of water. Spray plants until solution begins to run off the leaves. Three applications are recommended at 7 day intervals. Also, you can mix 2 tablespoons to a gallon of water and spray 2 or 3 times a week. This procedure will help the problem. Blossom rot stop (pre-mixed) chemicals are also available.

Cracking. Tomatoes can start to crack during warm, rainy periods, especially if rains follow a dry period. The tomatoes simply expand too fast and the flesh is exposed through the skin. Some varieties are resistant to cracking. Again, the best way to avoid the problem is to keep the moisture supply as even as possible throughout the season.

Catfacing. This is another kind of cracking or scarring in which tomatoes develop unusual swelling and streaks of scar tissue. This is not a disease. It is caused by abnormal development of the pistil (ovary from which the tomato develops) of the tomato flower at blossom time. Cool weather is believed to cause the flower abnormality.

High and Low Temperatures Affect Tomato Blooms. During some years many of the early-season as well as mid-season blossoms will simply fall off. When night temperatures fall below 55 F the tomato bloom pollen can be killed completely or so much is killed that complete pollination does not occur and misshapen, small tomatoes are produced. Many times this condition early in the season will only occur on the first one or two hands of tomatoes. High temperatures above 90F can also cause pollen damage but the location of damage from high temperatures is noticed on those blooms that were open at the time the high temperature occurred. The early maturing tomato varieties such as Spring Giant, Springset and Early Girl do not seem to be as susceptible to cold temperatures as do the main season tomatoes. Patio tomatoes such as Small Fry and Tumblin Tom likewise seem to tolerate lower temperatures. This explains why it is difficult to get a summer-long crop of tomatoes in the hot sections of the South.

Sunscald. 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. Some varieties develop a lot of foliage and so are good in hot, sunny areas of the country. To guard against sunscald, be careful not to over prune plants and remove all their shade.You can also grow them in cages where they will develop lots of protective foliage.

Although these common problems make tomatoes look ugly, the fruits are safe to eat. Just cut away the affected part and enjoy the rest.

Information posted April 30.