Why Won't My Tomato Plants Produce Very Much Fruit?

It's rare to find a home vegetable garden without tomato plants. Although they aren't hard to grow, tomatoes (Lycopersicon esculentum) have a few requirements that must be met before the plants can produce fruit. Temperatures that are too high or too low, too little sunlight or water, improper fertilization and flowers that aren't pollinated can all result in a disappointing crop. Although classified as tender perennials, tomatoes are grown as annuals in most of the country.

Sunlight and Water

  1. Tomatoes need at least six hours of sunlight a day to produce fruit, and the more sunlight they receive, the more fruit they produce. Evaluate the sunlight that your garden receives in summer when the surrounding trees and shrubs are in full leaf. Tomatoes also need 1 to 1.5 inches of water per week to prevent the flowers from drying up. In the absence of rain, use a soaker hose or apply water directly to the soil with a hose. Try not to wet the foliage and fruit.

Temperature and Humidity

  1. When temperatures are too high or too low, pollination doesn't take place and the flowers drop off without setting fruit. For optimum pollination, tomato plants need night temperatures between 60 and 70 degrees Fahrenheit. Night temperatures below 55 degrees can prevent pollen tubes from developing, and day temperatures above 90 degrees can cause blossom drop, preventing pollination. Prolonged periods of rain or high humidity also prevent fruit set, and dry air prevents pollination because the pollen can't stick to the stigma. Although temperature and humidity can delay fruit set, when conditions improve and new flowers bloom, the plant has another chance to set fruit.

Pollinating the Flowers

  1. Tomato plants are pollinated by wind. If there isn't good air circulation around the plants, you can help the process along by giving them a gentle shake from time to time. The best time of day to shake the plants is between 10 a.m. and 4 p.m. when the flowers are shedding the most pollen. If you have only a few plants, you can improve the odds of successful pollination by dabbing a small paintbrush or cotton swab from flower to flower.

Fertilizing Tomatoes

  1. Tomato plants are heavy feeders that need plenty of fertilizer to produce a good crop. Apply 2 pounds of 5-10-10 or 5-10-5 fertilizer per 100 square feet of garden area before planting tomatoes. Work it into the top 6 inches of soil. When the first fruits are about one-third their mature size, side dress with 5 pounds of 10-10-10 fertilizer or 3.5 pounds of calcium nitrate fertilizer per 100 feet of row. Work the fertilizer into the top inch of soil, taking care not to damage the roots. Don't overdo it. Too much nitrogen results in dark green, leafy plants that don't produce fruit.