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How to Grow Tomatoes: Complete Guide to Planting & Harvesting

red tomatoes ripening on the vine in the garden
Image Credit:
Helios4Eos/Getty Images
Botanical Name
Solanum lycopersicum
Grown as
Tender Perennial
USDA Zones
10a
10b
11a
11b
Toxicity
Toxic to Dogs and Cats
Sun Exposure
Full Sun
Water Needs
Moderate
Height
3-6 feet
Spread
3-6 feet
Soil pH
Acidic
Bloom Time
Summer
Flower Color
White
Yellow
Special Features
Container-Friendly
Long Blooming
Attracts Pollinators
Resilience
Heat-Tolerant
Plant Type
Vegetables
Written By: Catherine Boeckmann Executive Digital Editor and Master Gardener

Let’s be honest: store-bought tomatoes just can’t compete with the sun-ripened sweetness of one plucked from your own garden. Whether you’re dreaming of salsa, sauce, or that perfect BLT, growing tomatoes is the garden goal of summer. 

From tiny seeds to tangy fruits, we’ll walk you through every step to tomato glory. Get ready to dig in—your sandwich will thank you!

Tomato plants are tender, warm-season crops that love the sun and cannot bear frost. It’s important not to put plants in the ground too early. In most regions, the soil is not warm enough to plant tomatoes outdoors until late spring and early summer, except in Zone 10, where they are a fall and winter crop. See when to start tomatoes for your location.

Buy Seeds Now

Tomatoes take 60 days to more than 100 days to harvest, depending on the variety (see more about varieties below). Due to their relatively long growing season requirements (and late planting date), gardeners either 1) plant small starter plants from a reputable nursery or 2) start tomato seeds indoors to get a head start. 

Now, let’s dig into the complete guide to growing tomatoes!

Planting

When to Plant Tomatoes

Tomatoes are long-season, heat-loving plants that won’t tolerate frost, so wait until the weather has warmed up in the spring. See our Planting Calendar for when to start tomatoes in your location.

If you are starting tomatoes from seed, sow indoors 6 weeks before the last expected spring frost date in your area. Sow seeds 1/2 inch deep in small trays. Plant seedlings outdoors about 2 weeks after that date or when temperatures stay in the mid-50°F range both day and night. See our full guide to starting tomato seeds indoors.

If you have a long enough growing season, it is also possible to direct-seed tomatoes in the garden soil (1/2 inch deep)—but not before the soil is at least 55°F. Note that 70°F soil is optimum for maximum germination within 5 days.

Where to Plant Tomatoes

Select a site with full sun! In northern regions, 8 to 10 hours of direct sunlight are preferred. In southern regions, light afternoon shade (natural or applied, e.g., row covers) will help tomatoes to survive and thrive. Dig the soil to about 1 foot deep and mix in aged manure and/or compost. Give it 2 weeks to break down before planting.

Also, choose a space where tomatoes (and members of their family, especially eggplants, peppers, and potatoes) have not grown in the previous couple of years. See tips on crop rotation. 

Hardening Off Tomatoes

If you’re buying or growing the starter plants, you’ll need to harden off the seedlings for a week before transplanting them into the ground. Set them outdoors in the shade for a few hours on the first day. Gradually increase this time each day to include some direct sunlight. Learn more about hardening off seedlings.

Tomato seedlings

How to Plant Tomatoes

  • Transplant your seedlings (or your nursery-grown plants) into the ground outdoors after all danger of frost has passed and the soil is at least 60°F. See our Planting Calendar for suggested transplanting dates.
  • Place tomato stakes or cages in the soil when planting. Staking and caging keep developing fruit off the ground (to avoid disease and pests) and also help the plant to stay upright. See instructions on how to build stakes, cages, and tomato supports.
  • Optional: When you transplant tomatoes, add a handful of organic tomato fertilizer or bone meal (a good source of phosphorus) to the planting hole. Do NOT apply high-nitrogen fertilizers such as those recommended for lawns, as this will promote luxurious foliage but can delay flowering and fruiting.
  • When planting seedlings, pinch off a few of the lower leaves. Here are two ways to set seedlings in the soil:
    1. Place each root ball deep enough so that the bottom leaves are just above the surface of the soil. Roots will grow all along the plant’s stem underground. Plant seedlings 2 to 3 feet apart. Crowded plants will not get sufficient sun, and the fruit may not ripen.
    2. Alternatively, lay long, leggy transplants on their sides in trenches 3 to 4 inches deep. Bury the stems up to the first set of true leaves. Roots will develop along the buried stem. If you plant this way, consider setting four tomato plants in compass-point positions (north, south, east, and west). This formation enables you to fertilize and water the plants in the middle.
  • Remember to allow enough space for the plants to spread out.
  • Water well to reduce shock to the roots.

Spacing for Tomatoes

Growing Tomatoes in Containers

  • Use a large pot or container (at least 20 inches in diameter) with drainage holes in the bottom.
  • Use loose, well-draining soil (e.g., at least 12 inches of a good potting mix with added organic material).
  • A tray of some sort should be placed under the pot to catch any excess water that drains out the bottom.
  • Choose determinate types, such as bush or dwarf varieties. Many cherry tomatoes grow well in pots. Taller varieties may need to be staked.
  • Plant one tomato plant per pot and give each at least 6 hours of sun per day.
  • Keep soil moist. Containers will dry out more quickly than garden soil, so check daily and provide extra water during heat waves.
  • Learn more about how to grow tomatoes in containers.

Growing

Watering Tomatoes

  • Water in the early morning so that plants have sufficient moisture to make it through a hot day.
  • Water generously the first few days that the tomato seedlings or transplants are in the ground.
  • Then, water with about 2 inches (about 1.2 gallons) per square foot per week during the growing season. Deep watering encourages a strong root system.
  • Avoid overhead watering and afternoon watering. Water at the base/soil level of a plant to avoid splashing water on the leaves (which invites disease).
  • Mulch the plants 5 weeks after transplanting to retain moisture, keep soil from splashing the lower leaves, and control weeds. Apply 2 to 4 inches of organic mulch, such as straw, hay, or bark chips.
  • To help tomatoes through periods of drought, find some flat rocks and place one next to each plant. The rocks prevent water from evaporating from the soil.

Fertilizing Tomatoes

  • You should have already worked compost into the soil before planting and added some bonemeal to the planting hole when transplanting.
  • Side-dress plants, applying liquid seaweed or fish emulsion or an organic fertilizer every 2 weeks, starting when tomatoes are about 1 inch in diameter (some folks say golf ball-size). If you are using an organic granular formula such as Espoma Tomato-Tone (4-7-10 or 3-4-6), pull mulch back a few inches and scratch 2 to 3 tablespoons fertilizer around the drip line of the plant. Water in, and replace mulch.
  • Continue fertilizing tomatoes about every 3 to 4 weeks until frost.
  • Note: Avoid fast-release fertilizers and avoid high-nitrogen fertilizers. As stated, too much nitrogen will result in lush foliage but few flowers and little or no fruit.

Pruning Tomatoes

  • If growing vining tomatoes, pinch off suckers (new, tiny stems and leaves between branches and the main stem). This aids air circulation and allows more sunlight into the middle of the plant.
  • Gently tie the stems to stakes with rags, nylon stockings, twine, or soft string.
  • As a plant grows, trim the lower leaves from the bottom 12 inches of the stem.

Check out this post for even more tomato tips.

Tomatoes
Photo by Ozgurdonmaz/Getty Images

Harvesting

  • Leave garden tomatoes on the vine as long as possible.
  • Harvest tomatoes when they are firm and very red, regardless of size, with perhaps some yellow remaining around the stem. Harvest tomatoes of other colors (orange, yellow, purple, or another rainbow shade) when they turn the correct color.
  • If temperatures start to drop and your tomatoes aren’t ripening, use one of these methods:
    1. Pull up the entire plant, brush off dirt, remove foliage, and hang the plant upside down in a basement or garage.
    2. Place mature, pale green tomatoes, stem up, in a paper bag and loosely seal it. Or wrap them in newspaper and place in a cardboard box. Store in a cool (55° to 70°F), dark place. Cooler temperatures slow ripening; warmth speeds it. Check weekly and remove soft, spotted, diseased, or ripe fruit.
  • Never place tomatoes on a sunny windowsill to ripen. They may rot before they are ripe!
  • Watch this video for tips on how to ripen green tomatoes.
  • You can harvest seeds from some tomato varieties. Learn how here.

How to Store Tomatoes

  • Never refrigerate fresh garden tomatoes. Doing so spoils the flavor and texture that give them that garden tomato taste.
  • To freeze, core fresh and unblemished tomatoes and place them whole in freezer bags or containers. Seal, label, and freeze. The skins will slip off when they thaw.

See more on properly storing tomatoes and other vegetables.

Pests and Problems

Tomato Problems

If no flowers form, plants may not be getting enough sun or water. Too little of either can stop flowering.

If plants are producing abundant flowers but no fruit, it could be due to insufficient light, inadequate watering or irregular watering schedule, extreme temperatures (above 75°F during the night and 90°F during the day), or insufficient pollination by bees.

If flowers form but drop off the plant, this is due to high daytime temperatures (over 90°F). Provide shade during the hottest part of the day by using row covers or shade cloth.

Low humidity can also affect pollination. The ideal is 40 to 70 percent. If humidity is low, mist the plant to help pollen stick.

Tomato Pests

Tomatoes are susceptible to insect pests. To avoid overpopulation of insect pests, follow these basic tips:

  1. Monitor tomato plants daily, checking under leaves, checking fruit, and checking near the soil.
  2. To dislodge many pests like aphids, spray plants with a good jet stream from the hose.
  3. Handpick bigger insects like tomato hornworms with gloves on, dropping them into a bucket of soapy water.
  4. Apply insecticidal soap directly to the insect on the plant. This works for smaller pests, such as aphids and spider mites.
  5. Apply horticultural oils or sprays diluted in water. Neem oil sprays block an insect’s air holes.
  6. If you choose as a last resort to use insecticides like Sevin, keep in mind that you may be killing beneficial insects as well.

When it comes to tomato diseases and other problems, most of the work is in prevention. Here are some tips to avoid tomato diseases:

  1. Plant disease-resistant tomato varieties. Tomato disease-resistant codes are listed on seed or seedling packets (example: F = Fusarium Wilt).
  2. Rotate crops at least every 3 years in the same spot. Avoid planting other members of the nightshade (Solanaceae) family in the same area as well. This group includes potatoes, peppers, and eggplants.
  3. Ensure well-draining soil. Always mix in compost or organic matter.
  4. Water consistently! Do not overwater or underwater. Uneven watering may cause a condition called blossom end rot.
  5. Destroy infected plants. Unfortunately, you often need to remove and discard infected plants, or the disease will overwinter. Do NOT put them in your compost pile.
  6. Solarize the soil. If the problem is really bad, you can treat your soil by covering it with plastic during the hottest part of the summer for 6 to 8 weeks; the sun will destroy the bacteria.

Tomato Diseases

  • Blossom-End Rot causes the bottom side of the tomato to develop dark, sunken spots due to a calcium imbalance due to uneven watering. See the link for remedies and prevention.
  • Early Blight is a fungal disease that causes leaves to drop. In July, the risks of blight increase due to the combination of high humidity and warm days and nights. It starts with dark, concentric spots (brown to black), about 1/2 inch in diameter, on the lower leaves and stems. If you catch it early and destroy infected leaves, your plant may survive. The best defense for outdoor tomatoes is good ventilation and stripping off the lower leaves as the fruits develop. This also helps the ripening process, as tomatoes have maximum exposure to the sun.
  • Late Blight is a fungal disease that causes gray, moldy spots on leaves and fruit, which later turn brown. The disease is spread and supported by persistent damp weather. Unfortunately, once your tomato has late blight, there’s really no solution.
  • Mosaic Virus creates distorted leaves and causes young growth to be narrow and twisted, and the leaves become mottled with yellow. Unfortunately, infected plants should be destroyed (but don’t put them in your compost pile).
  • Fusarium Wilt starts with yellowing and wilting on one side of the plant and moves up the plant as the fungus spreads. Unfortunately, once this disease strikes, the plant needs to be destroyed.
  • Powdery Mildew is a fungal disease that leaves white spots or a dusting of white on the leaves. It can be managed. See the link to learn more.
  • Cracking: When fruit growth is too rapid, the skin will crack. This usually occurs due to uneven watering or uneven moisture from weather conditions, such as very rainy periods mixed with dry periods. Keep moisture levels constant with consistent watering and mulching.

See more information about Tomato Diseases and Disorders.

 

Types

The first job is deciding what to grow, and with at least 10,000 different varieties of tomato, there’s certainly plenty to choose from, including cherry tomatoes, paste types, varieties with standard round fruits, and chunky beefsteak tomatoes.

Whatever you grow, they’ll fall into one of two categories: ‘bush’ tomatoes, sometimes called determinate tomatoes, which grow to around 3 feet (1 m) tall, and ‘vining’ tomatoes, also called indeterminate or ‘cordon’ tomatoes, which continue growing to produce fruits on one long stem. Learn more about the difference between determinate and indeterminate tomatoes.

Do you only have a hanging basket? Hey, that’s no problem—there are compact tomatoes for this situation, too.

  • Determinate tomatoes, better known as bush varieties, grow 2 to 3 feet tall. These varieties tend to provide numerous ripe tomatoes at one time. They do not put on much leaf growth after setting fruit and tend to fruit for a (relatively) brief period of time. They are generally productive earlier than the vining varieties and not in the latter part of the growing season. Determinate tomatoes do not require staking or caging. These plants are ideal for containers and small spaces. Most paste tomatoes are determinate, which works well for making sauce and canning. Because they produce determinate tomatoes at the same time, they are a good selection for canning.  
     
  • Indeterminate tomatoes, better known as vining varieties, produce the largest types of mid- to late-season slicing tomatoes all summer and until the first frost. Because indeterminates experience more leaf growth, their production tends to be spread more evenly throughout the season. Indeterminate tomatoes need staking. They are ideal in large gardens. Most beefsteak and cherry tomatoes are indeterminate.
green zebra tomatoes
Tomatoes aren’t only red! The flavorful heirloom ‘Green Zebra’ is featured here, a high-yielding indeterminate plant. Credit: VZaitsev/GettyImages

Tomatoes come in a wide range of flavors, colors, and sizes. The choice also depends on how you use this versatile fruit in the kitchen. Cherry tomatoes are great for salads. Beefsteaks are great for sandwiches. 

Romas are not usually eaten fresh out of hand but are perfect for sauces and ketchup. See our separate Guide to Growing Roma Tomatoes.

Also, tomatoes can be susceptible to pests and diseases. To avoid problems, choose disease-resistant cultivars whenever possible. 

Early Varieties (fewer than 70 days to harvest)
Early-maturing cultivars such as ‘Early Girl’ may be slightly less flavorful but will produce fruit 2 to 3 weeks earlier than mid- or late-season cultivars. 

  • ‘Early Cascade’: indeterminate trailing plant, fruit in clusters; disease-resistant
  • ‘Early Girl’: indeterminate, meaty fruit; produces through the summer

Mid-season Varieties (70 to 80 days to harvest)

  • ‘Floramerica’: determinate; disease-resistant; firm, deep red flesh; strong plant
  • ‘Fantastic’: indeterminate; disease- and crack-resistant; meaty, rich flavor; heavy yields

Late-season Varieties (80 days or more to harvest)

  • ‘Amish Paste’: indeterminate; heirloom; large plum tomatoes, acorn-shaped fruit; juicy, excellent for sauce.
  • ‘Brandywine’: indeterminate; heirloom; beefsteak with perfect acid-sweet combination; many variants are available
  • ‘Tomato, Roma VF’: determinate; compact Roma tomatoes; resistant to wilts. Meaty interiors and few seeds; heavy-yielding; good for paste and canning.
roma tomatoes
Roma tomatoes. 
Credit: Ben185/Getty

Cherry Tomatoes 

  • ‘Sun Gold’: 57 days to maturity; indeterminate; resistant to Fusarium wilt and tobacco mosaic virus; bright tangerine-orange color on grapelike trusses; intensely sweet taste
  • ‘Matt’s Wild Cherry’: indeterminate, disease-resistant (including blight)
  • ‘Yellow Mini (F1)’: 57 days to maturity; indeterminate; sweet, juicy flavor; compared with other cherry tomatoes, Yellow Mini resists the splitting that is caused by too much rain or inconsistent watering; high resistance to tobacco mosaic virus.
yellow cherry tomatoes
Cherry tomatoes (‘Yellow Mini F1’). 
Credit: Johnny Seeds.

Large Tomatoes

  • Beefsteak, Beefmaster, Ponderosa, and Oxheart are noted for their large fruit. However, these larger-fruited types often are more susceptible to diseases and skin cracking.
black krim heirloom beefsteak tomato
 Black Krim heirloom beefsteak tomato. 80 days; indeterminate; wonderfully rich flavor. 
Credit: Park Seed.


Learn how to choose tomato varieties.

Wit and Wisdom

  • The tomato originated in South America. Spanish explorers brought the seed from the “New World” to Europe.
  • Initially, tomatoes were thought to be poisonous and only grown in the 19th century as an ornamental plant called “The Apple of Paradise” in Germany and “The Apple of Love” in France.
  • The mistaken idea that tomatoes were poisonous probably arose because the plant belongs to the nightshade family (Solanaceae), of which some species are truly poisonous.
  • In 1781, there is a record of Thomas Jefferson, an experimental farmer, raising tomatoes for his guests!
  • People have argued for quite a long time about whether tomatoes are fruits or vegetables!
  • Ease a headache by drinking tomato juice blended with fresh basil.
  • The various varieties of tomatoes range from as large as grapefruits to as small as marbles.
  • Compact tomato plants may be referred to as “dwarf,” “micro,” or “patio.”

Vegetables

About The Author

Catherine Boeckmann

Catherine Boeckmann

Executive Digital Editor and Master Gardener

Catherine Boeckmann loves nature, stargazing, and gardening, so it’s not surprising that she and The Old Farmer’s Almanac found each other. She leads digital content for the Almanac website and is also a certified master gardener in the state of Indiana.

Read more from Catherine Boeckmann

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Comments

<a title="View user profile." href="/author/editors">The Editors</a> Tue, 05/29/2012 - 16:30
Although several conditions may cause yellowing and wilting, the tomatoes may possibly have a type of wilt, perhaps fusarium or verticillium wilt. Symptoms begin as yellowing and wilting of lower leaves (verticillium often shows up as wedge-shaped yellow spots on the leaves). Plants can be stunted or not recover from wilting after being watered. To check for verticillium or fusarium wilt, cut a troubled stem by the base and look for brown discoloration inside the stem. Fusarium may affect just a few shoots in the beginning. It only attacks tomato plants, reduces vigor and yield, often killing the plant. Verticillium may affect whole plants and can travel to other types of plants. It may not kill tomato plants but will reduce vigor and yield. It’s best to destroy the plants (do not add to compost pile). In future, plant resistant cultivars. Sanitize tools. Rotate crops—avoiding any in the tomato/potato family in the same spot for the next few years. One can try soil solarization to try to get rid of the disease in the soil. Hope this helps. For more info and photos, see: http://ohioline.osu.edu/hyg-fact/3000/3122.html
<span>Anonymous</span> Thu, 05/24/2012 - 21:34
i ate a fresh tomatoes after i got it off the vine yes i did wash it off and i sliced it and put it on a sandwich and ever since i did this i have been sick what could have caused this
<a title="View user profile." href="/author/editors">The Editors</a> Wed, 05/30/2012 - 12:29
Fresh garden tomatoes do NOT naturally contain bacteria that can make you sick. Possibilities: Contact with raw food on cutting board, bacteria on your hands or in your sink, contaminated water or soil, improperly composted manure, etc. If you are still sick, please see a heath professional and take care!
<span>Anonymous</span> Sun, 05/13/2012 - 15:40
I couldnt help but notice how many people use fertilizer and are having trouble with their plants. I am using potting soil with a small amount of fertilizer in it (couldnt find any without), but I DO NOT use any extra. I have about 30 plants all ranging in height, but all very healthy. I might make compost tea, but really I find that fert is unnecessary. You're growing your own tomatoes so you dont have to buy the ones grown with pesticides at the store, right?
<span>Anonymous</span> Sat, 05/12/2012 - 10:41
I have several Celebrity plants growing...They are between 12"-24" tall. The 12" and a 16" already have Tomatos beginning to grow...(and yes I did mean 12 & 16 inches tall)Should I allow the fruit to mature or will it hurt the overall growth of the plant, since they are so small?
<a title="View user profile." href="/author/editors">The Editors</a> Mon, 05/14/2012 - 16:11
Celebrity tomato plants can get very tall (5 to 6 feet) and will get lots of tomatoes. Just make sure all the weight is supported with stakes/wire mesh or cages, preferably strong caging if budget allows.
<span>Anonymous</span> Thu, 05/03/2012 - 12:40
Hi, I thought of growing tomatoes in my small patio. This is my first trial. Can anyone help me like what all things i need to buy? like manure, fertilizer, seed, how to start with? how much to buy? And i need to grow in the cheapest way because as it is my first trial, i dont want to waste money if it fails. Guide me in detail. Thanks.
<a title="View user profile." href="/author/editors">The Editors</a> Thu, 05/03/2012 - 22:03
If you're growing tomatoes on a patio, it sounds as if you'd grow them in pots? You can certainly grow tomatoes in containers. Plant one tomato per container and make sure the container has holes in the bottom. Cherry tomatoes are great in containers and here are a few other smaller varieties to try: Early Girl, Patio, Small Fry, Sweet 100, Tiny Tim. Ask your garden center to advise on size of pots. Most tomatoes use large containers (18-gallon). Use potting soil (such as Miracle Grow), 1 cup of Osmocote slow release 13-13-13 and 1/4 cup of lime. Every 12 days, feed with a high phosphorous fertilizer. You can also add some mulch on top to retain moisture. Make sure your tomatoes are in a location where they will get 6 hours of sunshine daily. Water after planting and then consistently. When to water? If the soil is dry on the top, but you can feel moisture further down, you probably don't need to water them yet. If it feels dry all the way through, water them until the water leaks through the holes. You'll need to stake the tomatoes for support. You can find more detail about tomato plant care and harvesting on this page. Good luck!
<span>Darka Dusty</span> Tue, 09/06/2011 - 03:04
My great tomato experiment of 2011 has my husband & me totally confounded. I've been bugging my friend with ridiculously elementary questions... requiring her garden 'tech-support' so I don't really want to annoy her any longer. Maybe one of you can help? This was the first year we planted anything at all - three tomato plants. We had expert supervision when planting and followed all the advice we got. Recently someone told us to stop watering tomatoes at a certain time... which we did. Two days later, all the vines have all drooped. Garden Tech Support Friend said that's normal. Cool. I went outside just to see the extent of the 'droopage' and I noticed on one of the tomato plants that finally, after weeks of care, we had actual red tomatoes! I was so happy to see them, I picked all five or six of them, like a proud parent - and went to show my husband: We tried them - but they were mealy and mushy and not that sweet. So then I went to the other two plants, and indeed, down below and way in the back there more red ones. But the odd thing is, each of the three plants produced the exact same result. Smallish mealy mushy fruit, and the color was not the right red, more of a red/dark pink. They're all exactly the same - just a bit bigger than cherry tomatoes. We did everything right! Or maybe not!? Did we over water them? And if that's the case, now that we've stopped over watering them, will the future little green ones have any chance of being nice tomatoes? Or have we ruined all subsequent tomatoes too? The internet has lots of theories, but most of them say the reason is leaving them on the vine too long - which I know isn't the case with these. Now today I just heard that "Heritage" Tomatoes are having a bad year. Is that possible? I feel like apologizing to the plants and promising never to try to grow anything again. I'm a former New Yorker. Nature is the potted plant on your fire escape. Help.
<a title="View user profile." href="/author/editors">The Editors</a> Thu, 10/13/2011 - 14:45

Don’t get discouraged. All beginner gardeners have learning hurdles and even experienced gardeners never stop learning! We’re not sure where you live—and we wonder if it’s in a warm place. Here are a few common reasons for soft tomatoes:

1. If tomatoes are soft, usually it’s just overripe and you want to harvest sooner.
 

2. Or, if the temps have gone over 90 degrees and you let them fully ripen on the plant, they can become mushy.

3. Did you overfeed the tomatoes?  This is most likely is a nutrient imbalance, most likely too much nitrogen. Too much fertilizer with nitrogen or not enough potassium can be an issue.  If you buy a fertilizer, be sure to apply a 1:3 nitrogen-to-potassium liquid fertilizer.


We’re not sure why the tomatoes are smaller than you expected. Is it a ripening issue? Temps above 85*F and under 55*F will affect the ripening of tomatoes. If the temp is too low, the tomatoes can freeze overnight, causing them to become mushy as they thaw the next day (this is a sign of decay and means they are not safe to eat).

Did you get enough sun?  Tomatoes need a LOT of sun: 6 to 8 hours a day. Or, if it’s just size, that could be due to lack of moisture. You could also help growth by removing the small tomatoes and the stems and leaves that are offshoots to help channel energy into the rest of the tomatoes.

http://aces.nmsu.edu/ces/yard/2004/110604.html