Learn About Tomatoes

How to Sow

How to Sow and Plant

  • Sow tomato seeds indoors 6-8 weeks before the last frost in spring using a seed starting kit
  • Sow seeds ¼  inch deep in seed-starting formula
  • Keep the soil moist at 75 degrees F
  • Seedlings emerge in 7-14 days
  • As soon as seedlings emerge, provide plenty of light on a sunny windowsill or grow seedlings 3-4 inches beneath fluorescent plant lights turned on 16 hours per day, off for 8 hours at night. Raise the lights as the plants grow taller. Incandescent bulbs will not work for this process because they will get too hot. Most plants require a dark period to grow, do not leave lights on for 24 hours.
  • Seedlings do not need much fertilizer, feed when they are 3-4 weeks old using a starter solution (half strength of a complete indoor houseplant food) according to manufacturer’s directions.
  • If you are growing in small cells, you may need to transplant the seedlings to 3 or 4 inch pots when seedlings have at least 3 pairs of leaves before transplanting to the garden so they have enough room to develop strong roots
  • Before planting in the garden, seedling plants need to be “hardened off”. Accustom young plants to outdoor conditions by moving them to a sheltered place outside for a week. Be sure to protect them from wind and hot sun at first. If frost threatens at night, cover or bring containers indoors, then take them out again in the morning. This hardening off process toughens the plant’s cell structure and reduces transplant shock and scalding.

Planting in the Garden:

  • Select a location in full sun with good rich moist organic soil. Make sure you did not grow tomatoes, peppers, eggplant or potatoes in the bed the previous year to avoid disease problems.
  • Prepare the bed by turning the soil under to a depth of 8 inches. Level with a rake to remove clumps of grass and stones.
  • Tomatoes should be set 30-48 inches apart in a row with the rows spaced 3-4 feet apart. It can be tempting to space tomatoes more closely at planting time, but if you plant too closely you will increase the chance of disease, and decrease yields.
  • Dig a hole for each plant large enough to amply accommodate the root ball. 
  • Carefully remove the plant from its pot and gently loosen the root ball with your hands to encourage good root development. 
  • Tomatoes can be planted deeply, with the stem buried to the first set of leaves. The more deeply they are planted the more roots will form, providing the plant with additional support and better ability to take up nutrients. Some gardeners plant tomatoes by digging a horizontal trench and laying the plant in the trench with the top 2-4 inches of the plant pointing upward.
  • Fill the planting hole with soil to the top and press soil down firmly with your hand leaving a slight depression around the plant to hold water. 
  • Use the plant tag as a location marker. This is particularly important if you are trying different varieties. It is very difficult to tell which variety is which from the foliage.  
  • Water thoroughly, so that a puddle forms in the saucer you have created. This settles the plants in, drives out air pockets and results in good root-to-soil contact.
  • Place your plant support at this time. You can try tomato cages or staking. Unsupported plants will sprawl on the ground, require no pruning, and will probably produce a larger yield of smaller fruit than will staked plants. For larger, cleaner, more perfect fruits, support plants as they grow. Growing on stakes: Place strong stakes in the ground and set plants about 6 inches from the stakes. Growing in cages: Place a cage around a single plant; let the vines grow and enlarge within the cage, no pruning  will be necessary

How to Grow

How to Grow

  • Keep weeds under control during the growing season. Weeds compete with plants for water, space and nutrients, so control them by either cultivating often or use a mulch to prevent their seeds from germinating. 
  • Mulches also help retain soil moisture and maintain even soil temperatures. This is especially important for tomatoes as their roots may be easily damaged when weeding, and this can lead to blossom end rot.
  • Keep plants well-watered during the growing season, especially during dry spells. Plants need about 1-2 inches of rain per week during the growing season. Use a rain gauge to check to see if you need to add water. It's best to water with a drip or trickle system that delivers water at low pressure at the soil level. If you water with overhead sprinklers, water early in the day so the foliage has time to dry off before evening, to minimize disease problems. Keep the soil moist but not saturated.
  • If growing on stakes: As the plants grow, allow only one or two main stems to grow and pinch out any other side shoots as they form. Gently tie the one or two remaining shoots to the stake; don't pull them tightly against the stake. If growing in cages, no pruning is necessary.
  • Whether to remove the side shoots, or suckers, that grow out of the leaf axils or not depends on the support system used. Gardeners using stakes usually snap off these side shoots. They typically get earlier and larger tomatoes but overall production tends to be less. If tomatoes are grown in cages, the suckers are generally left on, although it's a good idea to pinch the tip out of them when they are 6-8 inches long. Regardless you may want to remove all the growth from the bottom 6-10 inches of the plant. This helps to improve air circulation and reduce the spread of diseases such as early blight. Wait until the plants are knee-high. In the morning when the plants have the most water in them, snap off the lower growth while it is small. Any plants that look sick with distorted foliage or have a mosaic pattern on the leaves should be removed as they may have a virus that can spread to the other plants. It is best to do this early in the season.
  • Monitor for pests and diseases. Check with your local Cooperative Extension Service for pest controls recommended for your area.

Growing tips

Harvesting and Preserving Tips

  • Determinate tomato plants ripen a heavy crop over a few weeks. Indeterminate varieties bear fruit continuously until frost. Remember that the days to harvest refers to the time from setting out transplants in the garden.
  • Pick tomatoes when they are as ripe as possible. They should be fully colored and firm and picked regularly to avoid overloading plants.
  • At the end of the season, when you know there will be a frost, pick all the almost-ripe tomatoes you can, and ripen them in brown bags or spread on newspapers at room temperature. Many cultivars will store for months. Store only sound fruit, at 50-60°F. Do NOT refrigerate and try to avoid having the fruit touch each other.
  • The foliage of tomatoes is toxic and should not be eaten.
  • Tomato fruits are enjoyed in many cooked dishes as a flavoring. Use them to make soups, sauces, stews, ketchup, paste, juice, quiche, and pies. Add them to curries, casseroles, and chutney.

Common Pests and Problems

Common Disease Problems

Anthracnose: This is a fungus disease that attacks the fruit as it is ripening. The first visible sign is a circular spot on the skin that is slightly sunken. The spots enlarge and turn black; the fruit rots. Extended periods of heat and humidity facilitate anthracnose growth. The fungus overwinters in diseased plant debris. Burpee Recommends: Plant resistant varieties, provide sufficient space between plants for good air circulation, avoid overhead watering which can spread the fungus spores, keep a clean garden, remove and discard all diseased plant material and rotate crops. Use a mulch to prevent spores from splashing from the soil onto plants.

Blight: Early Blight is a very common disease which causes brown concentric rings to appear on the lower leaves. The spots coalesce; the leaf turns brown and may drop off the stem. Leaf drop moves up the stem. Fruit does not grow to full size and is left exposed to possible sunburn/sunscald. This fungus overwinters in plant debris and weeds. Late Blight is another fungus disease that causes defoliation and fruit rot. Greasy, greenish-black, water soaked spots appear on the lower leaves. The spots enlarge and if the weather is wet they will look mildewed. Fruits develop dark rough spots. Rainy or cloudy days with temperatures of 70-80 degrees F and nights at 40- 60 degrees F provide ideal conditions for the rapid growth of this fungus. It is retarded by hot dry weather. The fungus is air-borne and can spread from diseased plants growing nearby. Burpee Recommends: Practice good garden hygiene at the end of the season and discard, do not compost, possibly diseased plants. Space plants to allow for adequate air circulation. Avoid overhead watering which may spread fungus spores. Plant in at least a 3 year rotation, do not alternate with plants in the same family (potatoes, peppers or eggplants). Plant resistant varieties such as ‘Cloudy Day’.

Septoria Leaf Spot: This disease causes severe losses in the Atlantic and Central states. It is most severe during rainy seasons in closely planted gardens. It usually appears when the plants begin to set fruit. Circular spots with gray centers and dark margins appear on the lower older leaves. Fungus spores are produced and darken the center of the spots. There is a progressive loss of foliage and fruits suffer from sunscald.  Burpee Recommends: Remove and destroy Infected plant debris. Don't handle or brush against plants when they are wet. Rotate plantings. Remove weeds growing nearby.

Wilt Diseases: Bacterial wilt is evidenced by rapid wilting and the death of the plant caused by soil-borne bacteria. There is no forewarning of yellow or spotted leaves. When the affected stem is cut near the soil line, the area is dark and oozes a gray slime. The wilt does not attack the fruit. The bacteria live in the soil and enter the plant through the roots. Control Measures: Do not grow plants in the same family in that area or nearby for 4 or 5 years. Continue to apply generous amounts of healthy compost to soil while fallow or support other crops. Fusarium wilt is one of the most damaging tomato diseases because of its spread during periods of hot weather. The first symptom of fusarium is the appearance of a few yellow leaves or a slight drooping of the lower leaves. Caused by a soil-borne fungus, the fungus enters through the roots and passes up into the stem producing toxic substances. This fungus is similar to verticillium wilt but will affect first one side of the plant and then the other. Burpee Recommends: Destroy affected plants at the first sign of fusarium; rotate crops and plant resistant varieties. Verticillium wilt causes a wilting of the leaves and stems on several branches. Leaf margins cup upward, leaves turn yellow and drop off. If fruit is produced, it is usually smaller than normal. Like fusarium this will enter through the roots, migrating up the stem and plugging a plant's transport vessels. It is transmitted in the soil. It can also be spread by water and tools. Burpee Recommends: Practice at least a 4 year crop rotation. Remove and burn crop debris. Plant resistant varieties. Walnut wilt causes overall wilting of plants, or dwarfed growth, in close proximity to black walnut tree. Some or all plants in a planting may be affected. Burpee Recommends: Do not plant tomatoes near black walnut trees. These trees exude a toxin from their roots which kills many plants.

Virus (Various causes): The most characteristic sign of virus is tight and dark green mottling of the leaves. Young leaves may be bunched. Young plants may have a yellowish tone and become stunted. Fruit is usually not affected in outward appearance, but it may be smaller and scarcer. Leaflets may point upward and have a grayish cast. Burpee Recommends: Plant resistant varieties. This disease is readily spread by handling. Destroy diseased plants and the plants on either side. Never smoke in the garden as tobacco mosaic virus can be transmitted from a smoker's unwashed hands while handling plants.

Common Pest and Cultural Problems

Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps who feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.

Blossom End Rot (BER): Blossom End Rot causes large brown or black dry or sunken spot(s) to appear, usually starting at blossom end (opposite the stem) of the fruit. Fruits often ripen prematurely. BER occurs when a plant cannot metabolize the calcium it needs to develop properly. This can occur when there is not enough calcium in the soil or when root damage and water stress reduce the uptake and movement of calcium through a plant. Occasionally, BER is the result of excessive nitrogen fertilization. It only takes a day for a lack of calcium to affect fruit, and that day can occur any time after blossom set.

  • Once a fruit has BER it will not recover. The plant is still healthy, just remove the affected fruit from the plant. The fruit is still good to eat if you remove the affected part.
  • BER most frequently occurs on fruit produced earlier and later in the season as this is when natural fluctuations in precipitation and cold weather occur. 
  • To avoid BER, properly site and prepare your garden bed before planting. Most crops need full sun and loose, well-drained organic soil. Make sure soil pH is slightly acidic, between 6.2 to 6.8, for optimum nutrient uptake. Test your soil to see if calcium is recommended. If it is, apply lime in the recommended quantity according to manufacturer's instructions. 
  • Avoid planting too early in cool soils as this can inhibit early root development, making the plant more susceptible to BER. Start with a quality transplant: a healthy seedling with strong roots will make a healthy plant.
  • Avoid wide fluctuations in soil moisture by applying 2-3 inches of mulch. This will moderate the release of water to plant roots, and also keep the soil from drying out when it is directly exposed to the sun. 
  • Avoid drought stress by making sure your plants get at least 2 inches of rain or water per week. Apply enough water to moisten more than the top inch of soil. Container grown plants will need more than 2 inches of applied-water per week in hot weather, check them daily if possible. Consider using drip irrigation or soaker hoses. One or two soakings are better than many light waterings.
  • Avoid over-fertilizing during the early fruiting stage, especially if the fertilizer contains high percentages of nitrogen. Use fertilizers especially formulated for tomatoes. These fertilizers have just the right amount of nitrogen and other micronutrients best for fruit production.
  • Avoid close cultivation around the base of plants when weeding. A layer of mulch should help prevent the possible disturbance or damage of fragile roots accidentally.

Fruit Cracking: This indicates that when the fruit was forming, it did not get an even supply of moisture from the roots. A sudden rush of water from sudden and heavy summer rains through the stem can pop the skin of a ripening fruit like an overfilled water balloon. The condition is particularly pronounced after a drought when a summer storm delivers a great amount of water to the tissues in the fruit. The skin cannot expand fast enough and cracks appear. The crack may rupture allowing the entrance of blight and rot. Burpee Recommends: Take care with your watering: instead of a quick sprinkle every day, water deeply once or twice a week (depending on rainfall) so the moisture soaks deeply into the soil where roots can take it up as needed. Soaker hoses can help here. Stick your finger into the soil every day to check that it is evenly moist a couple of inches below the surface. Always mulch tomatoes to keep moisture from evaporating, even in containers. 

Nematodes: Microscopic worm-like pests that cause swellings (galls) to form on roots. Plants may wilt or appear stunted. This is a serious problem in many Southern states. Burpee Recommends: Do not plant into infested soil. Grow resistant varieties. Try planting ‘Nema-Gone’ marigolds around your plants.

Tomato Horn Worm: Large, green caterpillars can quickly devour foliage. Burpee Recommends: With sturdy gloves on, hand pick them. If you see white projections coming from the back of the caterpillar, do not destroy it. These are the egg cases of a parasitic wasp that will destroy the caterpillar. These wasps should be allowed to remain in your garden.


Tomato FAQs

Why do I have lots of leaves but no flowers? The plant is likely getting too much nitrogen, which triggers it to grow foliage, and not enough phosphorus, which favors flowering and fruiting. Choose a fertilizer that has a balanced ratio of the three major elements, such as 10-10-10, or where the middle number (phosphorus) is larger than the first number (nitrogen) such as 2-3-1. Tomatoes are heavy feeders and usually do need fertilizer unless your soil is very rich. But follow manufacturer's directions to avoid overdoing it.

Why do I have flowers but no fruit? Flowers are aborting because of heat or cold or drought stress OR flowers are aborting because of a lack of pollination OR the plant is not ready to set fruit and the plant is self-aborting flowers to conserve and direct energy towards more growth.

Why are my fruits malformed? There are multiple causes for deformities but the two most common are catfacing and cracking. All are cosmetic only, the fruits are still edible. No tomato crop will ever be perfect. A certain amount of imperfection and loss is normal, though some years are tougher on tomatoes than others. However, many diseases and cultural reasons for misshapen tomatoes can be prevented. Properly choose, plant and care for your tomatoes; and let last year's challenge inform how you grow this year and this year's challenges inform how you grow next year. Bear in mind, too, that many older varieties prized for their flavor, such as 'Brandywine', are normally not perfectly red and round.

How do I grow tomatoes in a really hot climate? Tomatoes perform best when temperatures are between 50 and 90 degrees F. In warmer climates tomatoes cannot be grown in the heat of summer. Gardeners there grow them during their mild winters. Some varieties are more heat resistant than others: Arkansas Traveler; Heatwave II Hybrid; and Tasti-Lee.

Something is eating my tomatoes?!  Squirrels, skunks, possums, voles, birds and other small animals like tomatoes as much as people do. The only real way to protect a tomato crop is with a physical barrier such as a sturdy chicken wire or tomato cages. To be safe from diseases, discard animal-sampled tomatoes.

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