Answer: It could be that you are choosing the wrong varieties for your climate, or that your plants are not getting the nutrients they crave. Here's a little background on tomato plant habits:
Tomatoes are warm-season plants that grow best at temperatures of 70 to 80 F during the day and 60 to 70 F during the night.
The following tomato cultivars are recommended for South Carolina gardens. Most cultivars are indeterminate, (meaning they will continue to grow and produce fruit over a long season). Celebrity and Small Fry are determinate (they will grow and produce a single large crop, all at once).
Better Boy, Better Bush Improved, Big Beef, Celebrity, Early Girl, Park?s Whopper, Terrific. Cherry Type: Juliet, Small Fry, Super Sweet 100, Sweet Million. Plum Type: Viva Italia
Always choose varieties with disease resistance. Fusarium wilt is a common disease that can destroy a whole tomato crop. Many varieties are resistant to this disease. This is indicated by the letters VF after the cultivar name. VFN means the plants are resistant to Verticillium, Fusarium and nematodes; VFNT adds tobacco mosaic virus to the list.
The desired soil pH for tomatoes is between 5.8 and 6.5. Adding compost or topsoil to your sandy soil will help immensely. Tomatoes are heavy feeders. Use a starter solution for transplants. Sidedress when the first fruits are about the size of quarters, using 1 ? ounces of 33-0-0 fertilizer per 10 feet of row. Sidedress again two weeks after the first ripe tomato with a balanced fertilizer such as 5-10-5, and repeat this one month later.
It sounds as though your plants might be developing a disease if they grow well until just before harvest. Just to be on the safe side, plant this year's crop in a different garden location. Find the sunniest site possible. Poor fruit set occurs for several reasons, such as extreme temperatures, dry soil, too much shade and excessive nitrogen. Additionally, tomato blossoms are very sensitive to temperature. At temperatures of 55 to 60 F, pollination can be severely impaired and very few fruits will form. Temperatures of 90 to 95 F are also very unfavorable for pollination.
Hope this information helps guide you to a bountiful tomato harvest this summer!
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