Here are answers to some of the most common questions we receive about garden plants. You will find concise information on general gardening techniques as well as plant selection and care. For detailed information on specific plant pests and problems refer to our Common Garden Pests and Problems page.

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Horticulture Questions and Answers

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How do I grow tomatoes?

Tomatoes are the most popular crop in home gardens in St. Louis. With proper care you can achieve bigger yields of better tomatoes. As with all garden plants, weed control is critical to top performance. Several methods can be used. Cultivation by hoeing around the plants each week is effective, but do not cultivate deeper than 2 or 3 inches, as deep cultivation can damage shallow roots. Avoid working around plants when they are wet, as this can spread certain foliar diseases. Another method of weed control is by using mulch. Mulching has the added advantages of keeping the soil cool in hot weather, holding in moisture, and keeping the fruit cleaner. Organic mulches such as straw, leaves, compost or grass clippings work very well, and also will add organic material to the soil when they decompose. Apply mulch three to four inches deep and close to the plants. It is also recommended to apply additional nitrogen fertilizer if using an organic mulch. This counteracts the mulch's tendency to tie up available nitrogen as it decomposes. Apply one-fourth cup of ammonium nitrate, or similar nitrogen fertilizer per plant, about mid July, and again about two weeks later to insure good growth. You can also use black plastic or special paper mulch materials for mulching tomato plants. With these, roll the mulch out on the soil and set the plants in slits made at intervals along the row. Place soil, bricks or other materials on the mulch to keep it from blowing away.

Regular watering is critical for tomato production. Irrigate or water tomatoes to insure that they receive an inch of water a week. This is especially critical during dry spells when lack of adequate moisture can result in blossom drop, blossom end rot, and fruit cracking. Soak the soil thoroughly to a depth of 8 to 10 inches. Do not use light, frequent sprinkling.

If you have a small garden you may want to stake and prune your plants. This will produce a slightly earlier harvest and larger fruit. To stake, set a strong 3 or 4 foot long stake near each plant. When plants begin to branch, tie a strong cord firmly around the stake and loosely around the plant stem. Continue weekly as the plant grows. Train the plants to form only one or two stems by breaking off all shoots that develop between the leaves and the main stem as they appear.

Another staking method is to use tomato cages about 2 feet in diameter and five feet high, made of 6" concrete reinforcing wire. Caged tomatoes do not need to be pruned, only trained to stay within the cage. Caged plants will produce more, but smaller, tomatoes than staked plants.

Many gardeners have questions about the use of blossom set or hormone sprays to set tomato fruit. Hormone sprays will improve formation of early tomatoes when night temperatures are below 55 degrees. They are sold under various trade names and are available at nurseries and garden centers. Use according to package directions. They are not effective at setting fruit in mid-summer when tomatoes may fail to set fruit due to extended periods of temperatures above 85 degrees.