- Plant family: Solanaceae (Nightshades)
- Season: Warm
- Life Cycle: Annual
- Seed to first harvest: 60-85 days
The tomato is a member of the Solanaceae family, also known as nightshades, which includes crops such as the Irish potato, pepper, tomatillo, and eggplant (Figure 1).
The first wild tomato plant had bright red, cherry-type fruit and is thought to be native to the Andes Mountains region of Peru and Bolivia. Tomato spread to South America and Central America by the natural migration of Indigenous peoples. Confined to the Americas for several thousand years, it was bred and selected for larger fruit (which varied greatly in appearance), likely in Mexico beginning with the Aztecs and Toltecs. There it was traditionally companion planted with corn.
Christopher Columbus’s arrival in the New World prompted the spread of the tomato plant to Europe via Spanish explorers by 1550. In Spain the tomato was called “pome dei Moro” or “Moorish apple”; in Italy, “pomo d’oro” or “golden apple”; and in France, “pomme d’amour” or “apple of love.” Development of new varieties continued across those European countries, most popularly centralized around the Mediterranean region. English-speaking countries were skeptical of the fruit, as tomato is in the deadly nightshade family and the red color was thought to signify its poisonous nature. Tomato leaves and immature fruit contain the toxic alkaloid tomatine.
By the 1700s, tomato plants were grown in the U.S. by many gardeners, even Thomas Jefferson himself, but still the poisonous myth lingered. This cultural opposition began to change by 1812 with help from Creole cuisine in New Orleans, as tomatoes were fundamental for many dishes like gumbo and jambalaya. By the mid-1800s, tomatoes were commonly grown and used across the U.S. See Figure 2.
In the 19th century, the tomato had to overcome another myth that it caused cancer. This was eventually disproved by scientific evidence showing the contrary; it actually contains high levels of lycopene, an antioxidant that has cancer-fighting properties. This antioxidant is also found at lower levels in watermelon and grapefruit.
Today, tomato is the most commonly grown crop in a home garden and each American eats a yearly average of 23 pounds of processed tomatoes (e.g., ketchup, tomato sauce). Although the tomato is botanically a fruit, it is treated and classified as a vegetable.
Tomato varieties are grouped by plant growth habit: determinate or indeterminate (indicated in Table 1 with a “D” or “I” after the variety name). Determinate varieties (sometimes called bush types) generally produce fruit during a shorter harvest period (3-4 weeks), as stem growth stops at a “determined” height with a terminal (final) bud. In contrast, indeterminate varieties have a stem that continues to grow “indeterminately” until the frost, producing fruit progressively over a longer harvest period (5-6 weeks). Determinate varieties often grow 3-4 feet in height and indeterminate varieties grow 6-7 feet in height. Indeterminate varieties must be grown on a tall, strong trellis.
The thousands of tomato varieties can be divided into the following types: (1) fresh market and beefsteak, (2) heirloom, (3) Roma/paste, (4) grape and cocktail, and (5) cherry (see Figure 3). Tomato fruits ripen to a variety of colors, from the traditional bright red to yellow, orange, pink, green, or purple. Some varieties are selected for superior flavor or sweet-tasting fruit, heat tolerance (heat set), uniformity, productivity, or disease resistance.
Fresh market or beefsteak types produce more traditional, large, bright red, round tomatoes that are sometimes called “slicers” as they are used sliced on sandwiches and salads. Pink Girl and Carolina Gold are two fresh market/beefsteak varieties recommended for Louisiana that do not have red flesh. This type includes varieties with high disease resistance and average fruit weight.
Heirloom tomatoes are generally indeterminate, requiring trellising and pruning to manage the plants properly. Most varieties have little disease resistance and the fruit are usually thin-skinned, soft, and tend to crack. Heirloom tomatoes are attractive because many varieties are very flavorful, colorful, come in many sizes and shapes, and have interesting names. Greater care and management are required for heirloom types and if being grown organically, they should be grown in high tunnels for the greatest chance of success. There are hundreds of varieties of heirloom tomatoes available. Heirloom tomatoes include varieties whose seeds have been saved for at least 50 years and can be saved each season and replanted. In Table 1, varieties are grouped under heirloom even if they could have been categorized under another type based on size and shape. For example, popular heirloom varieties like Brandywine, Carbon, and Cherokee Purple are also larger and good for slicing like fresh market/beefsteak types. San Marzano is a famous Italian heirloom that is also used in the same way as other Roma or paste tomato varieties, and Yellow Pear is also a cherry tomato type. All of these are listed under heirloom.
Roma/paste tomato types include varieties with rather uniform, plum-shaped, medium red fruits, averaging 3-5 ounces. Varieties in this type have thick walls, few seeds, and good flavor; they are ideal for tomato sauce, paste, puree, ketchup, juice, and canning. All of the Roma/paste types recommended for Louisiana are determinate varieties and they are traditionally harvested in bulk, all at one time, and preserved.
Grape, cocktail, and cherry types are faster-growing and produce smaller fruits that vary in color (red, yellow, orange, purple-black) and weigh between 1/2-2 ounces. These types are generally very sweet-tasting and productive, with varying disease resistance. Grape and cocktail tomatoes include varieties that produce fruit at the higher end of the weight range and often have a more elongated shape. Sungold is a variety of cherry tomato that holds the title for the sweetest fruit, making them very popular among children.
Tomatoes have either open-pollinated (including heirloom) or hybrid varieties. All tomato varieties produce perfect, self-pollinating flowers (containing both male and female parts; see Figure 4), so there is usually no need to isolate different varieties when planting in order to save seed. For older varieties (heirlooms), it is recommended to separate different varieties by a distance of 10-50 feet to prevent cross-pollination (this difference is due to the flower structure of older tomato varieties).
If growing tomatoes in a greenhouse, it is recommended to select a greenhouse variety (indicated in Table 2). These varieties have been bred specifically for greenhouse conditions — lower light, higher humidity, and high temperature — and have better disease resistance than field types. Nearly all greenhouse varieties are indeterminate hybrids so that they will produce over a long harvest season. While non-greenhouse types can also grow in a greenhouse, the yield and quality may be reduced. In controlled environments (greenhouse or high tunnels), blowing/shaking of flowers or using bumble bees is required to ensure adequate pollination.
It is recommended to select disease resistant-varieties whenever possible. See the recommended tomato varieties for Louisiana in Table 1.
When and How to Plant
Tomatoes are warm season, frost-sensitive annuals. Tomato seeds should be started inside 6-8 weeks before the desired transplant date (refer to theTomato Planting Guide, Table 2). Using seed germination trays (with at least 1.5-inch diameter cells; larger cells work well for this crop too), plant 1 seed per cell at a shallow depth, about 1/8-inch deep; just deep enough to be covered with a thin layer of soilless potting mix. Seeds will germinate best in a warm, well-lit area in soil temperatures between 60-85 degrees F (tomato seeds will germinate very slowly in cooler soil). The minimum soil temperature for germination is 50 degrees F; maximum is 104 degrees F. It is important to keep soil moist, which usually requires daily light watering. A seedling heat mat and plastic dome lid are helpful in maintaining ideal germination conditions. Once several true leaves develop, it is recommended to move plants into larger, 3- to 4-inch pots to allow for more root growth before transplanting outside. At this stage, seedlings can be kept at 60-70 degrees F.
Tomato plants easily survive transplanting, but seedlings are susceptible to cold-shock and growth may be stunted if soil and air temperatures are too low. Aim to transplant outside when the temperature is between 65-75 degrees F (minimum temperature of 60 degrees F; there should be no danger of frost) and ideally during a cloudy day or planting late in the day or even at night to reduce wilt. A few days before planting transplants outside, it is recommended to follow a hardening-off process to transition seedlings to outdoor conditions. Refer to the Tomato Planting Guide (Table 2) for the recommended spacing when transplanting.
Tomato plants should be planted about 6 inches deep, or to the lowest leaf, as roots will form on the buried stem and this will encourage a stronger plant. This method will also correct a plant that has bent toward the sun to an upright position (see Figure 5).
Tomato plants are sensitive to cold temperatures below 50 degrees F and hot temperatures above 95 degrees F as this may cause blossom drop, poor fruit set, or cat-facing (deformed fruit). The optimum growing conditions are warm days (80-85 degrees F) and cooler nights (60-70 degrees F).
Table 2. TOMATO PLANTING GUIDE
|Transplant Outside Dates
|Days to Harvest*
|North LA: March 20-May 31
South LA: March 1-May 31
|Determinate: 1-2’ Indeterminate: 2-3’
|Determinate: 4-5’ Indeterminate: 5-6’
*First range of days: seed to first harvest; second range of days in parentheses: transplant to first harvest
Note: Table adapted from LSU AgCenter, UF Extension Planting Guides and Southeastern U.S. Vegetable Production Handbook
Where to Plant
Tomatoes are a warm season crop, and a well-drained clay or loam (sandy or silty) soil and full sun (6-8 hours/day) are recommended. Tomato plants prefer a soil pH between 6.0 and 6.8 but will tolerate acidic soil as low as 5.5. Avoid planting in heavy soils and low areas prone to flooding. It is recommended to plant tomatoes in box beds or in traditional raised garden rows that are about 6 inches tall to ensure good drainage and to prevent disease. In all types of gardens, it is recommended to add a 2- to 3-inch layer of compost, peat, rotted hay, or other organic matter and mix into the soil to optimize plant health. This is especially important for tomato plants as they thrive in soil high in organic matter, phosphorus, and calcium (to prevent blossom-end rot, use calcitic lime or gypsum if needed). Be sure the soil is not too high in nitrogen.
Reflective plastic mulch — or a plastic fabric/film mulch — is recommended to increase soil temperature, yield, fruit size and quality, while controlling weeds. White plastic is recommended for growing tomato plants in temperatures above 85 degrees F, as this will keep the soil cooler during warm weather fruit production. Black plastic is only recommended for cooler climates and during the spring in Louisiana. Drip irrigation is also recommended when using plastic mulch to maintain ideal soil moisture and to encourage productive plants.
Each season, rotate plant families — avoid planting crops from the same plant family in the same area of the garden — to reduce disease and pests. A longer crop rotation of 4 years is recommended for Solanaceous crops like tomatoes to reduce pest pressure and risk of disease.
Check for adequate soil moisture every 2-3 days. The soil should remain moist, but take care to not oversaturate as this encourages blossom-end rot. Drip irrigation helps to meet the high-water demand for this crop, about 1-1.5 inches per week depending on soil type and temperature, which is especially important during the fruiting stage. Deep watering is important to strengthen the root system. If plants are stressed for adequate water, this will significantly impact tomato production.
Insufficient potassium may lead to yellow shoulders on fruit and a tough, white core during hot summer temperatures. Blossom-end rot, a very common tomato nutritional disorder, is caused by lack of calcium. Soil may have sufficient calcium levels, but if the gardener fails to water enough, calcium may not be dissolved in the soil for root uptake. If watering practices are corrected and blossom-end rot persists, conduct a soil test and discuss results with a local county extension agent.
Organic fertilizers such as compost, fish emulsion, composted poultry litter or manure, worm castings, and blood or bone meal originate from living organisms. They are far more environmentally sustainable and safe than traditional synthetic fertilizers. They naturally release nutrients more slowly and over a longer period of time. When applying organic fertilizer, it is important to use in unison with compost, cover crops, and crop rotation, which all work together to build soil health. Learn how to convert inorganic fertilizer recommendations to organic fertilizers here.
Alternatively, a synthetic fertilizer may be used at a rate of about 1.5 pounds (3 cups) of 13-13-13 for every 25 feet of row or 75 square feet. Broadcast, or sprinkle evenly, over the soil and then mix in about 3-6 inches deep using a rake. Supplemental sidedressing, or reapplication of synthetic fertilizer, is recommended when the first immature fruits are visible. Sidedressing is the addition of fertilizer to the soil around already established plants when the plant begins to fruit or vine, primarily to provide nitrogen. When using synthetic fertilizer, sprinkle 2 tablespoons around each plant, keeping it about 6 inches away from the plant stem; water into the soil. Indeterminate tomatoes require the application of additional sidedressing every 3-4 weeks until the end of the crop. Fish emulsion is a good, quick-release source of nitrogen if using organic fertilizers.
Staking of tomatoes improves fruit quality by keeping plants and fruit off the ground, and they are easier to harvest than ground tomatoes. Determinate tomato plants are often staked even though the stems do not grow tall. Indeterminate tomato plants must be supported to train the stem to grow vertically and support the weight of the fruit on very tall stems; this will also optimize yield and fruit quality. There are many options to support tomato plants, but cages are not recommended as they prohibit air circulation and increase risk for disease. Here are three methods to support tomato plants:
- Use one wooden stake per tomato plant (recommended for a few plants). Drive 4- to 5-foot (determinate) or 8-foot (indeterminate) by 1-inch square wooden stakes into the ground (about 12 inches deep) before transplanting at the recommended plant spacing intervals (about 24 inches). One transplant should be planted beside each stake. Once the seedlings are 12-15 inches tall, secure to the stakes using an elastic nylon band, tying in a loose loop to prevent future stem girdling. Continue securing the plants to the stakes for every 12-15 inches of growth. See Figure 6 and this video on the method; start at 3:30.
- Use the Florida Weave Technique (recommended for a row of plants). Place a metal T-post at the end of each row and one in the middle; then place 4- to 5-foot (determinate) or 8-foot (indeterminate) by 1-inch square wooden stakes between every few tomato plants. When the plants are 12-15 inches tall, use garden, tomato, or nylon twine to run lines about 10 inches above the soil. On each side of the row of plants, weave between each plant, and tie the twine to the stakes. In this method, the plant is never tied to the twine or stake. It is recommended to weave additional levels of trellis for every 12-15 inches of plant growth, or about 12 inches above the last support weave. Watch this helpful video tutorial on the Florida Weave System.
- Use a vertical trellis (recommended for a row of plants; minimal staking required). Drive metal T-posts that are 8-10 feet tall about 2 feet into the ground between every 4-5 tomato plants. This will likely require a T-post driver or pounder tool. Then, hang a heavy single-strand wire (about 9 gauge) between each post or attach another structure above. From this wire/structure, hang garden, tomato, or nylon twine down to each tomato plant. Attach the twine to the base of each plant in a very loose knot that won’t be at risk for choking the stem as it grows. Start wrapping the stems around the string early, taking care not to pinch the leaves, and continue to do so as the plants grow. In this method, the plants are never tied to stakes or posts (see Figure 7). This video is helpful in showing how to set up the vertical trellis; this video describes the process of winding twine around the stems. For someone who is more skilled in carpentry, this video shows a simple but more sturdy design for a vertical tomato trellis that could function as a permanent addition to a raised garden bed.
Suckering and Pruning
Pruning and suckering are essential for optimal fruit size and yield, while also controlling pests and preventing disease. Pruning is practiced to establish a desired balance between vine growth and fruit growth. Little to no pruning results in a plant with a heavy load of smaller fruit. Moderate pruning results in fewer fruits that are larger and easier to harvest. Pruning can result in earlier maturity of the crown fruit and improves spray coverage and pest control. The amount of pruning that is recommended is dependent on the specific variety, the season, and growing conditions.
Removing suckers is an ongoing process of removing the buds or suckers that would produce additional side shoots off the main plant stem. Suckering can be done by pinching off shoots by hand unless they have grown more than a few inches; then sharp snips or clippers should be used to prevent damage to the plant during removal. See Figure 8.
Indeterminate varieties should be pruned to one or two main stems, removing all suckers along those main stems. It is generally not recommended to prune determinate varieties as they have a limited stem growth, are generally bushier, and are less vigorous. For all varieties, be sure to prune the lower leaves/stems to keep the base of the tomato plants clear; there should be no leaves touching the ground.
Plastic mulch will control most of the weeds; hand-pull weeds close to the plant, especially in the planting holes. Organic mulches such as hay and straw may also be used to control weeds in plant rows.
Insect Pests and Disease
Aphids and thrips are common insect pests for tomato plants and can transmit harmful viruses like tomato spotted wilt virus and tobacco mosaic virus. Tomatoes are susceptible to viruses (e.g., tomato spotted wilt virus and tobacco mosaic virus), fungal diseases (e.g., anthracnose), and physiological disorders (e.g., blossom-end rot and sun scald). Many tomato varieties are resistant to specific diseases, and these should be selected and planted — especially if the garden has been afflicted by one or more diseases in previous growing seasons. Generally recommended tools for prevention are using reflective mulch; avoiding overhead irrigation; and crop rotation. See Table 3 to aid in diagnosis and management of some common tomato insect pests and diseases.
Table 3. Organic and Natural Management for Common Tomato Insect Pests and Diseases
|Organic and Natural Pest Management
|• Occurs before fruit set
• Irregular brown-black elongated cankers or spots on stem
• Dark brown sunken lesions with concentric rings on green fruit
• Stem girdling and collapse
|Alternaria stem canker
|• Wet, humid conditions
• Black spots on fruit
|• Curled and yellowed leaves
• Stunted crops
• Sticky honeydew on leaves
|• Warm, humid conditions
• Small yellow-green, water-soaked spots on lower, older leaves
• Older spots become brown-black with yellow halo
• Yellowed leaves; defoliation
• Blossom drop and yield loss
|Bacterial leaf spot
|• Green-yellow or black sunken spot on bottom of fruit
• Premature fruit ripening
• Calcium deficiency
• Drought stress; root damage
• Over-irrigation; high humidity
|• Soil-borne fungus
• Leaf blight and defoliation; low-quality fruit; sun scald
• May cause collar rot, stem canker, and fruit rot
|• Small, irregular holes in leaves
• Concentrated damage in young plants and seedlings
• Stunted plants; reduced yield
|• Larvae and caterpillars bore into fruit and eat leaves
• Hornworms have a horn on the back end; green with stripes
• Fruit decay and rot
|Hornworm and fruitworm
|• Soil-borne fungus
• Fast-spreading and sporadic
• Mild, moist weather
• Irregular, water-soaked dark lesions on leaves that enlarge to green-black blotches
• White, downy fungal growth on underside of lesions
|• Small, yellow larvae
• Tunnels inside leaves with white trails
|• Uneven distribution of stunted plants
• Pale green/yellow leaves; wilt
• Root galls, knots, swellings
|• Girdled stem
• Plant wilt and death
• White fungal growth; mustard seed-like structures at plant base
|• Humid climate
• Defoliation and sunscald
• Small, dark brown specks on leaves that expand to spots with a yellow halo
• Lesions enlarge and center turns gray and cracked
|Stemphylium gray leaf spot
|• Transmitted by aphids
• Mottled (mosaic) light and dark green foliage
• Stunted plants
• Uneven fruit ripening; yield loss
|Tobacco mosaic virus
|• Transmitted by thrips
• Black, irregularly shaped lesions on leaves
• Discolored or lesioned fruit
• Stunted plants; wilt
|Tomato spotted wilt virus
|• Transmitted by whiteflies
• Yellowed and distorted leaves
• Stunted plants; small leaves; bushy appearance
• Reduced yield; blossom drop
|Tomato yellow leaf curl virus
|• Leaf discoloration and wilt
• Tiny white flies flutter when plants are disturbed
• Sticky honeydew on leaves
• Black, sooty mold fungus
|• Plants wilt and die
• Brown streaks inside root and stem when split lengthwise
• Bacterial wilt is transmitted by the cucumber beetle
|Wilt (bacterial, Fusarium, Verticillium)
Note: Table adapted from LSU AgCenter; Texas A&M AgriLife Extension; UMass Extension; Alabama A&M and Auburn Universities Extension; Connecticut Agricultural Experiment Station; University of California; and University of Tennessee Extension. The Louisiana Pesticide Law regulates the use of pesticides in schools to protect children and staff from harmful exposure to chemicals and is enforced by LDAF. The recommended alternative to routine pesticide use is Integrated Pest Management (IPM), which combines pest control, disease management techniques and organic/natural alternatives, many of which are found in this table.
Harvest and Storage
Tomatoes may be harvested unripe and green, or at any stage of ripeness, usually marked by a color change to red, pink, orange, yellow, or purple. Fruit can be harvested with just a blush of color, as ripening continues after harvest. For the best-quality taste, harvest ripe fruits that are firm, glossy, and easily dislodge from the plant. Harvest the fruit by hand, lifting from the plant. Remove the pedicel (stem) to encourage ripening and to prevent the bruising of other fruit. During peak production, tomatoes may be harvested 2-3 times per week for at least 3-4 weeks for determinate varieties or 5-6 weeks for indeterminate varieties, or until fruit production stops. The fruit is bruised easily and should be handled with care postharvest.
Ripe tomatoes stored at 50-70 degrees with high humidity (85-95%) will hold for 4-7 days; green or partially ripe tomatoes for 1-3 weeks. Take care not to store tomatoes below 50 degrees F as they are cold sensitive, and taste and texture will be adversely affected.
Preserve tomatoes by canning, drying, or freezing.
Tomatoes are Nutritious and Good for You
Good source of Vitamin A
Important for eye health, a strong immune system, and cell growth
High in Potassium
Essential for body function, especially the heart, kidney, nerves, bones, and muscles
Rich in Vitamin C
Important for bones, skin, blood vessels
Contains the carotenoid Lycopene
Antioxidant that may prevent cancer and improve heart health
Louisiana Harvest of the Month recipe: Tomato Cucumber Salad
Video on how to cut tomatoes
Common methods of preparing and cooking tomatoes
Taste-testing ideas: bruschetta, salsa, chili, roasted tomato soup, spaghetti sauce, baked tomatoes with cheese, Panzanella
Other websites with many tomato recipes:
- Southeastern Vegetable Extension Workers, 2020 Southeastern U.S. Vegetable Crop Handbook
- LSU AgCenter, Louisiana Vegetable Planting Guide
- LSU AgCenter, Louisiana Commercial Vegetable Production Recommendations
- LSU AgCenter, Vegetable Gardening Tips: Tomatoes
- UF Extension, Planting Guide
- UF Extension, Vegetable Production Handbook of Florida
- Texas A&M AgriLife Extension, Vegetable Varieties for Central Texas
- Texas A&M AgriLife Extension, Easy Gardening: Tomatoes
- Texas A&M AgriLife Extension, Commercial Crop Guides: Tomato
- UT Extension, Plant Diseases: Foliar Diseases of Tomato
- Connecticut Agricultural Experiment Station, Stemphylium Gray Leaf Spot of Tomato
- Alabama A&M and Auburn Universities Extension, Bacterial Spot of Tomato and Pepper
- Alabama A&M and Auburn Universities Extension, Blossom-End Rot in Tomatoes: Causes and Prevention
- Alabama A&M & Auburn Universities Extension, Crop Production,
- UMass Extension Vegetable Program: Disease, Insect, and Mites Fact Sheets
- UC IPM, Agriculture: Tomato Pest Management Guidelines, Tomato Yellow Leaf Curl
- Texas Cooperative Extension, Gardening Fact Sheet: As American as Tomatoes, a History of Tomatoes
- Texas A&M AgriLife Extension, Aggie Horticulture: The Tomato Had To Go Abroad To Make Good
- Purdue Extension FoodLink: Tomato
- Maynard, Donald N & Hochmuth, George J (2007). Knott’s Handbook for Vegetable Growers (5th edition). John Wiley & Sons, Inc.
- Decoteau, Dennis R (2000). Vegetable Crops. Prentice-Hall, Inc.
- Swiader, John M & Ware, George W (2002). Producing Vegetable Crops (5th edition). Interstate Publishers, Inc.
- Sukprakarn, S, Juntakool, S, Huang, R, and Kalb, T (2005). Saving your own vegetable seeds—a guide for farmers. AVRDC publication number 05-647. AVRDC—The World Vegetable Center, Shanhua, Taiwan. 25 pp.
- Seed Savers Exchange, A Guide to Isolation Distances
- University of Georgia Extension, How to Convert an Inorganic Fertilizer Recommendation to an Organic One, Circular 853