Tomato Questions Answered



Spring is here, and it’s time to think tomatoes. Consider the following information to get the best possible crop.

Tomatoes are categorized by maturity class (early, mid-season or late), fruit shape or size (cherry, pear, plum or large), plant size (determinate, semi-determinate or indeterminate), fruit color (red, pink, yellow, orange) and use (fresh, process or dual use). When selecting varieties, consider the growing environment, primary use and available growing space. Most garden centers and nurseries carry varieties that have been proven to grow well and produce high quality, flavorful fruits for local conditions.

Tomatoes can be grown from seeds or transplants. Transplants should have five to seven mature leaves and a well-developed root system. Transplants mature about four weeks before seeded tomatoes and are recommended for most growing areas in Utah.

Tomatoes prefer a sunny location and fertile, well-drained soils. Incorporate plenty of organic matter and a complete fertilizer into the area before planting. Once planted, avoid heavy fertilization, which encourages excessive foliage growth and delays fruit maturity. Side dress with one tablespoon of nitrogen (34-0-0) per plant at four and eight weeks after transplanting.

Plant tomato seeds directly in the garden 10-14 days before the last frost date. Plant four to five seeds ½ inch deep at the recommended plant spacing and later thin the weaker plants. Most gardeners transplant tomatoes through black plastic for earlier maturity. Use row covers or hot caps to protect the plants when planting before the frost-free period. Space tomatoes 2 feet apart in the row with rows 2-3 feet apart.

Plant three to four tomato plants per person for fresh use and an additional five to 10 plants for juicing, canning or freezing. Expect 100 lbs. of fruit per 100 feet of row.

Irrigation should be deep and infrequent. Apply 1-2 inches of water per week. Use drip irrigation if possible. Place mulch around the plant to conserve soil moisture and reduce weed growth. Do not apply organic mulches until soils have warmed to 75 F. Irrigate so that moisture goes deep into the soil. Irregular watering (over or under) can cause blossom-end rot, a dark leathery spot on the bottom of the fruit.

Use wooden stakes or wire cages to support semi- or indeterminate plants. Staking helps reduce sunburned fruits and keeps ripening fruits off the ground. Drive stakes 18 inches into the soil, 3-4 inches from the stem. Indeterminate varieties require more support and vine pruning to keep plant size manageable. Continue to tie up plants as they grow.

Control insects and diseases throughout the year. Common problems are tomato horn worm, aphids, fusarium and verticilium wilt. Always identify the problem before using a pesticide. Your local county Extension office can help identify the problem and offer solutions.

Tomatoes require 25-35 days to mature from flowering, depending on the temperature and variety. For best flavor and quality, pick fruits when they are fully colored but firm, and pick as they ripen. At the end of the season, harvest all fruits that are mature green or slightly colored. Store at 55 F and use as they ripen. Ripe tomatoes will store for one to two weeks if held at 50-55 F. Fruits are subject to chilling injury, so do not store them for more than a few days in the refrigerator.

The following are answers to recent tomato questions.

Q: What causes the flowers to drop off my tomato plants?
A: During unfavorable weather (night temperatures lower than 55 F or day temperatures above 95 F), tomatoes do not set and flowers abort. The problem usually disappears as the weather improves.

Q: What can I do to prevent my tomatoes from cracking?
A: Some varieties are more prone to cracking than others. Many newer hybrid varieties are quite resistant. Severe root or vine pruning increases cracking. Keep soil moisture uniform as tomatoes develop and plant resistant varieties to minimize the problem.

Q: On some of my tomato plants, the leaves are turning yellow and the plants are no longer growing. Also, the fruits are ripening prematurely, and are leathery and bitter. What is wrong?
A: Tomatoes with these symptoms are infected with the curly top virus, a disease transmitted by the beet leaf hopper. Once infected, there is very little you can do. Since the severity of curly top varies from year to year, planting a few more plants than required will compensate for potential losses. Plant varieties resistant to curly top include Roza, Columbia, Rowpac and Saladmaster.

Q: Why are the new leaves on my tomato pointed, cupped, twisted and irregular in shape?
A: Your tomatoes may have been injured by 2,4-D or a similar growth regulator weed killer. Never use the same sprayer in your vegetable garden that you use for weed control in your lawn. Use caution when applying lawn care chemicals near vegetables or fruits. If applying grass clippings to the garden, make sure the herbicides used are safe for food plants. Consult with your lawn care professional to ensure the chemicals applied to your lawn will not affect your edible garden plants.

Posted on 15 Apr 2005

Dan Drost
Vegetable Specialist

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