What do tomatoes need to grow?

Jaime BeamerMarch 6, 2023

0 73 9 minutes read

Tomatoes are one of the most popular crops among home gardeners, and with good reason: not only are tomatoes delicious and versatile, they are relatively easy to grow and return high value for the space they occupy. No store-bought tomato can compete with the taste of a vine-ripened tomato plucked at its height of freshness from the garden.

Tomato is a perennial plant native to Central and South America that belongs to the nightshade family (Solanacae). The tomato first debuted in European cuisine in the 16th century, but it did not become popular until the 18th century due to the widespread assumption that it was harmful.

Contents

Soil Requirements

Tomato plants thrive in well-drained soil that receives full light for the most of the day. The pH of the soil should be somewhat acidic (6.2 to 6.8). Excess nitrogen may cause plants to have lush, robust foliage but produce little fruit. Although it is best to determine lime and fertilizer needs from the results of a soil test, a rule of thumb for gardeners lacking test data is to apply 2½ pounds of a complete fertilizer such as 10-10-10 (or the equivalent) per 100 square feet of garden area. 2 weeks before planting, work the fertilizer into the soil.

Selecting the Right Variety

There are hundreds of tomato types to suit every temperature, garden location, and taste. There are types of tomatoes that mature in 55 days and others that take three months of hot weather to yield a harvest. Some grow vines that will spread 25 feet if not pruned, while others are barely 8 inches tall when mature. Fruit may be as little as pebbles or as enormous as grapefruits. And the range of hues! With so many options, how can you choose the one or ones that are best for your garden?

Choose cultivars that have been developed to thrive and yield well in our short growing season. A good way to do this is to choose varieties that have been tested under local conditions.
Is the variety’s growth habit definite or indeterminate? Tomato plants that are determined to grow to a given height and then cease. They blossom and set fruit in a very short amount of time. Indeterminate tomato types thrive, blossom, and produce fruit throughout the growing season. The vines continue growing throughout the season too, so these varieties should be staked, caged or pruned.
What will you do with the tomatoes? Do you need huge fruit for slicing? Fruits of medium size to slice or chop into salads and salsas? Miniature sweet fruits for lunchboxes? Tomatoes for preserving, juicing, or drying? Many gardeners continue growing old-fashioned, “heirloom” varieties that have been favorites for generations because of their exceptional flavor or unusual appearance.
Resistant to diseases, stressors, and disorders might be an essential concern, particularly for farmers who have already encountered these issues. Many variety names are followed by one or more letters indicating resistance to Verticillium wilt (V) or Fusarium wilt (F) diseases, for example, and some varieties are less likely to experience problems such as cracking and yellow shoulders.

Most gardeners do not grow their own tomatoes from seed and are thus confined to the variety available at local garden stores. Inquire with salespeople, study label descriptions, and chat to other gardeners about which tomato types they favor and why. Whether you purchase seedlings or grow your own, experiment with two or three different tomato varieties each year for fun and adventure.

Purchasing Tomato Seedlings

Tomatoes must be started inside six to eight weeks before being transplanted permanently into the garden due to their extended growth season and temperature needs. Choose stocky plants with robust, straight stems and vivid green leaves when buying tomato seedlings. The ideal transplant is less than six inches tall, as broad as it is high. Choose tall, lanky plants or huge, well-established plants with noticeable blooms or fruits.

Plants growing in cell packs or individual containers are better choices than those growing in flats, as their roots will suffer less transplant shock. Insects and visual symptoms of illness should be absent from seedlings.

Hardening Off

Harden off tomato seedlings before transferring them into the garden, whether they are bought or produced from seed. Set plants outside for a few hours each day for about ten days before transplanting to gradually adapt them to outdoor circumstances. Begin by placing plants in filtered light in an area that is shielded from strong gusts. Extend the time the tomato seedlings spend outside each day, gradually exposing them to direct sunshine and wind. Remember that seedlings lose water much more rapidly outdoors than inside and will need more frequent watering during the hardening off process.

Bring plants indoors at night and on days when the temperature falls below 60 degrees Fahrenheit. Below this temperature, tomatoes experience chilling injury, which can delay their growth and may cause a condition called “catfacing” on early fruit.

Transplanting

When planting tomatoes in the garden, wait until the risk of frost has gone and soil temperatures have risen to about 60°F. Throughout much of New Hampshire, Memorial Day weekend is a safe time for transplanting tomatoes, though southern gardeners may often plant a week or two earlier and growers in the northern frost pockets may need to wait until mid- June.

The appropriate spacing for tomato plants is determined on the variety’s growth behavior and if the plants will be pruned:

Staked or caged plants should be spaced 18 to 24 inches apart in rows at least 5 feet apart.
Unstaked determinate plants should be spaced 12 to 24 inches apart in rows 4-6 feet apart.
Unstaked indeterminate plants should be spaced 2 to 3 feet apart in rows 5-7 feet apart.

Use a trowel to dig a hole about twice the size of the tomato seedling and its root ball; set the seedling into the ground at the same level as it grew in its container. Make certain that the root ball is completely covered. If seedlings are growing in peat pots, peel back the rim of the pot so the entire pot is buried below the soil surface, because an exposed peat pot will wick moisture from the soil.

Irrigate the newly-set transplant well with water or a weak fertilizer solution to prevent transplant shock and speed seedling establishment.

Container Growing

Tomatoes may be grown in containers when space is restricted or the circumstances are unsuitable for tomato cultivation. Although any large container will work as long as it provides adequate drainage; a general recommendation is to plant one tomato plant per four or five-gallon container. Containerized tomatoes should be grown in artificial potting mix rather than conventional garden topsoil or homemade compost. Since container-grown tomato plants do not have access to the deep soil reservoir of water and nutrients, pay extra attention to water and fertilizer requirements. Most containerized tomato types need the use of a stake, trellis, or other support.

Cultural Practices

An even moisture supply throughout the development of the fruit helps avoid a condition known as blossom end rot, as well as delivering the water required to grow the fruit – too much water at any one moment may cause ripening fruit to split.

Pruning, or selectively removing some of the tomato plant growth, can improve harvestable yields and prolong the harvest season. It may also aid in the treatment of various diseases. The best pruning method depends on whether the tomato is determinate or indeterminate. Please consult the fact sheet Pruning Tomatoes for additional information on pruning procedures. Install pegs or cages during planting time, rather than later when the plants’ roots have formed.

Commercial growers often produce tomatoes in unheated greenhouses known as high tunnels. Keeping the plants covered keeps the leaves drier, which minimizes the prevalence of leaf diseases such as early blight and Septoria leaf spot. Growing tomatoes under cover can also increase crop yields and quality, while allowing you to work in the crop in inclement weather. Inexpensive temporary tunnels, sometimes called “caterpillar tunnels” are one way to create such a cover for tomatoes, and this strategy may be worth considering if you have a history of crop losses from diseases.

Mulch is often used at the base of tomato plants by many farmers. Plastic mulches assist to retain soil moisture, increase soil temperature early in the season, and regulate soil temperature throughout the summer. Black plastic mulch reduces weeds and protects the fruit of unstaked plants from soil contact. Organic mulches provide the same moisture retention, weed suppression, and fruit protection benefits as plastic mulches, and ultimately disintegrate, providing organic matter to the soil’s supply. Tomatoes may be mulched with a two to four-inch-deep layer of organic mulch made of straw, pine needles, or leaves. Since organic ingredients slow soil warming, do not apply these mulches until the soil is completely heated.

Common Problems

Flea beetles Young tomato plants may be attacked. Protect new transplants from this insect during their first two or three weeks of growth with spun-bonded floating row covers. Since tomato seedlings are delicate, wrap the row cover over wire hoops or a simple wooden frame to keep it from falling on the plants.

Cutworms are soil-dwelling caterpillars that feed on stems at or just below the soil level, essentially cutting off transplants at the base. This damage may be avoided by wrapping a protective cutworm collar one inch deep and two inches high around each freshly planted transplant. A small paper cup with the bottom removed or a cut-to-size length of stiff paper or plastic, folded into a cylinder and secured with a paper clip are two inexpensive ways to fashion cutworm collars. If you have a large number of plants to protect and a major infestation, you may also consider using cutworm bait.

Hornworms are big, green caterpillars that feed on tomato leaves (and occasionally fruit). In New Hampshire, there are two species: tobacco hornworm and tomato hornworm. Because they blend in with the tomato foliage, it can often be hard to see them until after they have done a lot of damage. They are readily controlled by using a biological pesticide or by manual removal. Please see the fact sheet: Hornworms on Tomatoes in New Hampshire for additional information.

Septoria leaf spot, Early blight, and Late blight are all fungal tomato illnesses. Septoria leaf spot (Septoria lycopersici) and early blight (Alternaria solani) fungus overwinter in the soil on plant detritus. These are frequent causes of tomato leaf spots, with symptoms often appearing on the lower leaves. Septoria is generally more severe since it produces defoliation of the plants as well as spots on the stems and petioles. Late blight, caused by Phytophthora infestans, does not overwinter in our soils, and arrives via storms each year, usually late in the season. While it does not form leaf spots, it can blight leaves, stems, and fruit and may swiftly destroy plants. If you believe fungal infections are wreaking havoc on your tomato crops, you must first identify the illness in order to properly control it. Call our Infoline at 1-877-EXT-GROW (1-877-398-4769) for assistance in identifying issues, or send samples to the NH Plant Diagnostic Laboratory.