Answer: Most gardeners would agree that there is nothing quite like home-grown tomatoes to make a green salad perfect. However, I often hear from people who have healthy and vigorous tomato plants in their gardens, yet little or no fruit to show for their efforts. While it's tempting to blame poor fruit production on nutrient deficiencies, pests and diseases, the problem is most often a result of blossom drop and poor pollination.
Despite the fact that tomatoes evolved in the tropics, flowering in tomatoes is sensitive to temperature. For many varieties, when day temperatures exceed about 92 degrees F and night temperatures exceed 68 degrees F, tomato flowers often drop. Temperatures that go below 55 degrees F at night can also prevent pollination of tomatoes. An important temperature factor is time of exposure. The longer the plants are exposed to high temperatures, the more serious the effect will be on flowering. High temperatures for several consecutive days, coupled with dry soil conditions, will often lead to poor pollination and flower drop. Hot drying winds and low humidity can make the problem worse. Heirloom and older home garden varieties are more sensitive to temperature related problems than are many of the newer hybrids.
Shading may also account for poor tomato fruit set. Be sure to locate your tomato plants where there will receive at least six hours of direct sun a day. Any less direct sunlight will result in a spindly, nonproductive plant.
Excessive tomato vine growth is usually associated with poor blossom set. Anything that stimulates lush vine growth usually discourages flower set. The most common cause of too much growth is excessive nitrogen fertilization. If you have made heavy applications of manure or commercial nitrogen fertilizers, your tomato plants may be growing beautifully but not producing much fruit. This problem is often corrected as the season progresses and some of that excessive nitrogen is used up by the plant or leached from the plant root zone.
Another often overlooked cause of poor fruit set in tomato plants is simply dry soil. If your tomato plants are not receiving adequate water, the plants become stressed, and blossoms may dry and fall off plants. Be sure to keep tomato plants watered. This means a regular watering schedule that prevents the soil from drying out too much at any one time. You may want to mulch the soil beneath your tomato plants to help prevent moisture loss, especially during very hot days.
Tomato fruit set problems are fairly common wherever tomatoes are grown. You can improve your chances for good crops by choosing varieties adapted to your growing region, planting in full sun and watering and fertilizing properly.
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