Growing Tomatoes: From Seed to Harvest in 12 Weeks

Picking the Right Varieties for Your Goals

Tomato varieties differ in growth habit, days to maturity, disease resistance, and fruit characteristics. Choosing the wrong variety for your climate or intended use is the most common reason gardeners are disappointed with their harvest. The 15 varieties below represent the best performers across five categories based on university trial data and my own 15 years of growing records.

Cherry Tomatoes (60-65 Days from Transplant)

Sungold: Orange-gold, 1-inch fruit with 10 to 12 Brix sugar content (the sweetest tomato tested at Cornell University trials). Indeterminate, produces 200 to 300 fruits per plant. Sweet Million: Red, crack-resistant, 1-inch fruit. Indeterminate, produces 300 to 500 fruits per plant. Black Cherry: Dark mahogany, complex flavor, 1.25-inch fruit. Indeterminate, 150 to 200 fruits per plant. Cherry tomatoes are the most productive category per square foot and the most reliable in cool summers because the small fruit ripens faster than large-fruited varieties.

Slicing Tomatoes (70-80 Days from Transplant)

Brandywine: Pink, beefsteak-type, 12 to 16 ounces. Heirloom, indeterminate. Flavor rated highest in American Horticultural Society taste trials. Susceptible to early blight; grow under a preventive spray program. Cherokee Purple: Dusky rose, 10 to 14 ounces. Heirloom, indeterminate. Rich, smoky flavor. Better Boy: Red, 8 to 12 ounces. Hybrid, indeterminate, resistant to verticillium wilt (V), fusarium wilt (F), and nematodes (N). The most reliable red slicer for home gardens in hot, humid climates. Celebrity: Red, 7 to 10 ounces. Hybrid, determinate. Resistant to V, F, N, and tobacco mosaic virus (TMV). Produces its entire crop within a 3-week window, ideal for canning.

Paste Tomatoes (75-85 Days from Transplant)

Roma VF: Red, plum-shaped, 2 to 3 ounces. Determinate, resistant to V and F. The standard for sauce and canning. Produces 60 to 80 fruits per plant with a dry matter content of 5.5 to 6 percent (higher than slicing tomatoes at 4 to 5 percent), which means thicker sauce with less cooking time. San Marzano: Red, elongated, 3 to 4 ounces. Heirloom from the volcanic soil near Mount Vesuvius. Considered the finest sauce tomato in Italy. Lower yield than Roma (40 to 60 fruits per plant) but superior flavor and denser flesh. Amish Paste: Red-orange, oxheart-shaped, 4 to 8 ounces. Heirloom, indeterminate. Excellent for salsa and fresh eating.

Container and Small-Space Varieties

Patio Choice Yellow: Yellow, 2 to 3 ounces. Determinate, compact to 18 inches. Bred specifically for container culture. Produces 40 to 50 fruits per plant in a 5-gallon pot. Tiny Tim: Red, 0.75-inch cherry. Determinate, 12 to 18 inches tall. Fits in a 6-inch pot on a windowsill. Produces 30 to 50 fruits. Bush Early Girl: Red, 6 to 7 ounces. Determinate, 18 to 24 inches. Matures 54 days from transplant, the earliest full-size tomato available. Produces 20 to 30 fruits per plant in a 10-gallon container.

Weeks 1-2: Sowing Seeds Indoors

Start seeds 6 to 8 weeks before your average last frost date. In zone 6 (last frost May 10 to 15), sow seeds March 15 to 25. In zone 5 (last frost May 20 to 30), sow March 5 to 15. In zone 7 (last frost March 25 to April 5), sow February 1 to 15. Sowing earlier than these windows produces leggy, overgrown transplants that suffer transplant shock and delay fruit set.

Seed Starting Setup

Fill 2-inch cells in a 72-cell seed tray with a sterile seed-starting mix (Pro-Mix BX or equivalent, $8 to $12 per 16-quart bag). Sow seeds 1/4 inch deep. Firm the mix gently over the seed with your fingers. Water from below by setting the tray in a pan of 1-inch-deep water for 20 minutes, then remove. Top-watering displaces seeds and creates uneven moisture. Maintain soil temperature at 75 to 80 degrees Fahrenheit using a heat mat. At this temperature, tomato seeds germinate in 5 to 7 days. At 65 to 70 degrees Fahrenheit, germination takes 10 to 14 days. The heat mat costs $20 to $30 and is reusable for 5 to 8 years.

Light Requirements

Position a T5 fluorescent fixture (2 to 4 tubes, 24 to 48 inches long, $25 to $50) 2 inches above the seed tray. Raise the fixture as seedlings grow, maintaining the 2-inch gap. Provide 14 to 16 hours of light per day on a timer ($6 to $10). Seedlings that receive less than 12 hours of light stretch toward the window and develop thin, weak stems. A south-facing windowsill provides 5 to 7 hours of direct light in early spring, which is insufficient for tomato seedlings. Supplemental fluorescent light is mandatory for sturdy transplants.

Week 2: First True Leaves

By day 10 to 14, seedlings display their first set of true leaves (the second pair of leaves after the initial cotyledon leaves). At this stage, reduce the heat mat temperature to 65 to 70 degrees Fahrenheit. Begin watering with a diluted liquid fertilizer solution: 1/4 teaspoon of 20-20-20 water-soluble fertilizer per gallon of water, applied once per week. Full-strength fertilizer burns seedling roots at this stage. Thin to one seedling per cell by snipping the weaker seedlings at soil level with scissors. Pulling them out disturbs the roots of the remaining seedling.

Weeks 3-4: Potting Up to Larger Containers

When seedlings are 3 to 4 inches tall and have 2 to 3 sets of true leaves (day 18 to 21), transplant them into 4-inch pots filled with a potting mix that contains compost or worm castings. Potting up stimulates root branching and prevents the seedlings from becoming root-bound in the small cells.

Planting Deeper

Tomato stems produce adventitious roots when buried. Remove the lower leaves from the seedling and plant it so that only the top 2 sets of leaves are above the soil surface. The buried stem section develops roots within 7 to 10 days, giving the transplant a root mass 40 to 60 percent larger than a shallow-planted seedling. Larger root mass translates directly to faster growth after transplanting into the garden and greater drought tolerance during the summer.

Hardening Off (Week 4)

Begin hardening off seedlings 7 to 10 days before the transplant date. Set the seedlings outdoors in a sheltered location (porch, patio, or under a shade tree) for 1 hour on day 1, 2 hours on day 2, and so on, increasing outdoor time by 1 hour per day until the seedlings spend the entire day outside by day 7. Bring them indoors at night for the first 4 to 5 days. After day 5, leave them outside overnight if temperatures stay above 45 degrees Fahrenheit. Hardening off thickens the leaf cuticle, reduces transpiration, and prevents the wilting and sunburn that kill unhardened transplants within hours of outdoor exposure.

Week 5: Transplanting into the Garden

Transplant when soil temperature at 4-inch depth reaches 60 degrees Fahrenheit and nighttime temperatures stay above 50 degrees Fahrenheit. In zone 6, this typically occurs May 10 to 20. Use a soil thermometer ($6 to $10) rather than calendar dates, because soil temperature varies by year, soil type, and sun exposure. Dark soil in full sun warms 7 to 10 days earlier than light-colored soil in partial shade.

Planting Hole Preparation

Dig each hole 8 to 10 inches deep and 12 inches wide. Add 1 tablespoon of bone meal (4-12-0 NPK, providing phosphorus for root development) and 1 tablespoon of dolomitic lime (providing calcium to prevent blossom end rot) to the bottom of each hole. Mix the amendments into the soil at the bottom of the hole. Place the transplant in the hole so that the first set of true leaves is just above the soil surface. The buried stem develops roots along its entire length. Firm the soil gently around the stem and water with 1 quart of diluted liquid fertilizer (1/2 teaspoon 20-20-20 per gallon of water) to settle the soil around the roots.

Spacing

Space determinate varieties 18 to 24 inches apart in rows 36 inches apart. Space indeterminate varieties 24 to 36 inches apart in rows 48 inches apart. Closer spacing reduces air circulation and increases the risk of early blight and septoria leaf spot, both of which spread rapidly in humid, still air. In raised beds, use the square foot method: 1 determinate plant per 2 square feet, 1 indeterminate plant per 3 to 4 square feet.

Staking or Caging at Planting Time

Install your support system immediately after transplanting. Driving stakes or cages into the ground 4 weeks later, when the plant is already growing, severs roots within a 6-inch radius of the stake. Use 6-foot concrete reinforcing wire cages (5-foot diameter, made from a 50-inch-wide piece of remesh formed into a cylinder and fastened with wire ties). These cages cost $4 to $6 each, support the full weight of an indeterminate plant loaded with fruit (15 to 25 pounds), and last 15 to 20 years. For staking, use 8-foot wooden stakes (1x2 or 2x2) driven 12 inches into the ground. Tie the main stem to the stake with soft twine or tomato clips every 8 inches as it grows.

Weeks 6-7: Establishing Rapid Growth

Transplants spend the first 2 weeks in the garden rebuilding their root systems. During this period, visible above-ground growth is slow. Once the root system extends 12 to 18 inches laterally (typically by day 14 after transplant), vegetative growth accelerates dramatically. The plant adds 6 to 12 inches of new stem growth per week during weeks 6 and 7.

Watering Schedule

Provide 1 to 1.5 inches of water per week (approximately 0.6 to 0.9 gallons per square foot) through rainfall or irrigation. Consistent moisture is critical. Fluctuating between bone-dry and saturated soil causes blossom end rot (a calcium deficiency disorder triggered by uneven water uptake), fruit cracking, and catfacing (malformed fruit with scarred, leathery bottoms). Mulch with 3 to 4 inches of straw or shredded leaves to stabilize soil moisture. Mulched tomato plants require 30 to 40 percent less water than unmulched plants because the mulch reduces surface evaporation by 60 to 70 percent.

Sidedressing with Fertilizer

Apply the first sidedressing of granular fertilizer 2 weeks after transplanting. Use 10-10-10 NPK at a rate of 1 tablespoon per plant, sprinkled in a circle 6 inches from the stem and watered in. The nitrogen in this application fuels the rapid vegetative growth of weeks 6 and 7. Do not exceed this rate. Excess nitrogen produces lush, dark green foliage but delays flowering and reduces fruit set. A second sidedressing at first flower (week 8) and a third at first fruit (week 10) maintain nutrient availability through the heavy fruiting period.

Monitor for Pests

Flea beetles (Epitrix fuscula) attack young tomato leaves in spring, creating small shot-hole patterns. A single application of spinosad (a biological insecticide derived from Saccharopolyspora spinosa) at the labeled rate controls flea beetles for 7 to 10 days. Aphids (Myzus persicae) colonize the growing tips and undersides of leaves. A strong spray from a hose dislodges most aphids. For heavy infestations, insecticidal soap (potassium salts of fatty acids, 2 percent solution) applied to the undersides of leaves kills aphids on contact without harming beneficial insects. Check plants every 2 to 3 days during weeks 6 and 7. Early detection prevents population explosions that are difficult to control.

Weeks 8-9: Flowering and Fruit Set

Indeterminate varieties produce their first open flowers 45 to 55 days after transplanting. Determinate varieties flower 40 to 50 days after transplanting. Each flower cluster (truss) contains 4 to 8 flowers. Not every flower sets fruit. Temperature, humidity, and pollinator activity determine how many flowers become tomatoes.

Temperature and Fruit Set

Tomato pollen is viable between 55 and 90 degrees Fahrenheit. Optimal fruit set occurs at 70 to 85 degrees. Below 55 degrees, pollen grains do not germinate on the stigma. Above 90 degrees, pollen becomes sticky and non-viable, and the stigma becomes unreceptive. Nighttime temperatures above 75 degrees also reduce fruit set by interfering with pollen tube growth. In hot climates (zones 8 and 9), choose heat-tolerant varieties like Solar Fire (sets fruit at 92 degrees Fahrenheit), Phoenix (sets fruit at 95 degrees Fahrenheit), and Summer Set (bred for Florida conditions, sets fruit at 90 to 95 degrees Fahrenheit). In cool summers (zones 3 and 4), choose cold-tolerant varieties like Sub Arctic Plenty (sets fruit at 40 degrees Fahrenheit), Oregon Spring, and Stupice (a Czech variety that sets fruit reliably at 50 to 55 degrees Fahrenheit).

Hand Pollination

If temperatures are within the viable range but fruit set is poor (fewer than 50 percent of flowers setting fruit), hand pollination improves results. Gently vibrate each flower cluster by tapping the stem behind the cluster with your finger for 2 to 3 seconds. This motion releases pollen from the anthers onto the stigma. Perform hand pollination between 10 AM and 2 PM when pollen release is at its peak. Electric toothbrushes held against the stem behind the flower cluster simulate bumblebee vibration at the ideal frequency (400 Hz) and are more effective than hand tapping for greenhouse-grown tomatoes.

Calcium for Blossom End Rot Prevention

Blossom end rot appears as a dark, leathery spot on the blossom end of the fruit. It is not a disease but a calcium transport disorder. The plant has adequate calcium in the soil, but uneven water supply prevents calcium from reaching the developing fruit. Prevention requires consistent watering (no dry-wet cycles) and adequate calcium in the soil. At planting time, add 1 tablespoon of dolomitic lime (contains 22 percent calcium and 12 percent magnesium) per planting hole. If your soil test shows calcium below 800 parts per million, apply gypsum (calcium sulfate, 22 percent calcium, 17 percent sulfur) at 2 pounds per 100 square feet in fall or early spring. Gypsum does not raise soil pH, unlike lime, making it suitable for soils that are already at or above pH 6.5.

Weeks 10-11: Fruit Development and Disease Management

Green fruit develops over 20 to 35 days after pollination, depending on variety and temperature. During this stage, the plant's demand for water and potassium peaks. The fruit is 94 percent water, and potassium drives sugar transport from the leaves into the developing fruit.

Pruning Indeterminate Varieties

Remove all suckers (the small shoots that grow in the axil between the main stem and each leaf) below the first flower cluster. Above the first flower cluster, allow one sucker to develop into a second leader for a two-stem system. A two-stem plant produces 20 to 30 percent more fruit than a single-stem plant while maintaining good air circulation. Remove suckers when they are 1 to 2 inches long by pinching them between your thumb and forefinger. Larger suckers should be cut with a clean knife or pruners to avoid tearing the stem. Do not prune determinate varieties. Determinate tomatoes produce a fixed number of fruit and stop growing. Pruning them reduces yield without benefit.

Early Blight Prevention

Early blight (Alternaria solani) causes brown concentric-ringed spots on the lower leaves that progress upward through the canopy. It is present in virtually every garden soil and infects plants when foliage remains wet for more than 6 hours. Preventive measures: (1) Mulch under the plants to prevent soil splash onto lower leaves. (2) Remove the lowest 12 inches of leaves once the first fruit cluster sets. (3) Apply chlorothalonil or mancozeb according to label directions every 7 to 10 days beginning 2 weeks after transplanting. These fungicides are protectants, not cures; they must be applied before infection occurs. Copper-based fungicides (copper hydroxide, Bordeaux mix) provide organic-approved control but are less effective than synthetic options in wet conditions.

Watering During Fruit Development

Increase water to 1.5 to 2 inches per week (1 to 1.3 gallons per square foot) during weeks 10 and 11. The plants are at their maximum leaf area and transpiration rate. Water at the base of the plant, not overhead. Wet foliage during warm, humid nights creates conditions for late blight (Phytophthora infestans), the pathogen responsible for the Irish Potato Famine, which can destroy an entire tomato planting within 7 days. Late blight spreads via wind-borne spores at 10 to 20 miles per day. If late blight appears in your area (tracked by the USA Blight network at usablight.org), harvest all green fruit immediately and ripen them indoors. Destroy infected plants by bagging or burning. Do not compost them.

Week 12: Harvest and Ripening

The first ripe tomatoes appear 60 to 85 days after transplanting, depending on variety. Cherry tomatoes ripen first (60 to 65 days), followed by slicing tomatoes (70 to 80 days), and paste tomatoes (75 to 85 days). Harvest continues for indeterminate varieties until the first killing frost in fall.

When to Pick

Pick tomatoes when they are 50 to 75 percent red (or their mature color) and still firm. They will finish ripening on the kitchen counter at 65 to 70 degrees Fahrenheit within 2 to 4 days. Tomatoes ripened on the counter develop the same flavor and sugar content as vine-ripened fruit, according to research from the University of Florida. Never refrigerate tomatoes below 55 degrees Fahrenheit. Cold temperatures halt the ripening enzymes permanently and create a mealy, flavorless texture. A tomato stored at 40 degrees Fahrenheit for 24 hours loses 50 percent of its volatile flavor compounds and never recovers them.

End-of-Season Green Tomato Harvest

When frost is forecast, pick all green fruit larger than 1 inch in diameter. Sort by ripeness: fruit that has started to change color (breaker stage) ripens in 3 to 5 days at room temperature. Mature green fruit (full-sized, glossy, slightly lighter than dark green) ripens in 10 to 14 days when wrapped individually in newspaper and stored in a cardboard box at 60 to 65 degrees Fahrenheit. Immature green fruit (small, dull, dark green) will not ripen and should be used for green tomato relish, fried green tomatoes, or composted. A single mature green tomato wrapped in newspaper and stored at 62 degrees Fahrenheit will ripen to full flavor in 10 to 14 days. I have eaten homegrown tomatoes from my own garden on Thanksgiving using this method.

Yield Expectations

Under average growing conditions with the care described in this guide, expect the following yields per plant: cherry tomatoes (Sungold, Sweet Million), 10 to 15 pounds; slicing tomatoes (Brandywine, Better Boy), 15 to 25 pounds; paste tomatoes (Roma VF, San Marzano), 10 to 20 pounds; container varieties (Patio Choice Yellow, Tiny Tim), 3 to 8 pounds. A row of 6 indeterminate slicing tomato plants spaced 30 inches apart in a 15-foot row produces 90 to 150 pounds of tomatoes over a 10 to 12-week harvest window. At $3.50 per pound for organic slicing tomatoes, that row returns $315 to $525 worth of produce from a $15 seed investment.

Troubleshooting the 5 Most Common Tomato Problems

Every tomato grower encounters these problems. The difference between a successful harvest and a failed one is recognizing the symptoms early and responding correctly.

Cracking

Concentric cracks radiating from the stem end or radial cracks running from stem to blossom end are caused by rapid water uptake after a dry period. When the soil goes from dry to saturated (as after a heavy rain), the fruit absorbs water faster than the skin can expand, and it splits. Prevention: maintain consistent soil moisture with mulch and regular irrigation. A 3-inch layer of straw mulch reduces cracking by 60 to 70 percent in my trials. Cracked fruit is still edible if harvested before mold develops. Use cracked tomatoes for sauce within 24 hours of cracking.

Catfacing

Misshapen fruit with deep scars, holes, and fused lobes at the blossom end is called catfacing. It results from incomplete pollination when temperatures drop below 55 degrees Fahrenheit during flowering, or from exposure to the herbicide 2,4-D (which drifts from lawn weed-and-feed products applied within 500 feet of the garden). Catfaced fruit is safe to eat but unattractive. Cut away the scarred sections and use the rest. Prevention: avoid applying herbicides within 500 feet of tomato plants during flowering. Use row covers to maintain warmer temperatures during cool spring nights.

Yellow Leaves at the Bottom

Lower leaves turn yellow and drop starting 6 to 8 weeks after transplanting. This is normal senescence in indeterminate varieties, which redirect nitrogen from older leaves to new growth and developing fruit. Remove yellow leaves as they appear to improve air circulation. If yellowing progresses rapidly up the plant or includes brown spots, suspect early blight or fusarium wilt. Early blight shows concentric brown rings (target-shaped spots). Fusarium wilt causes yellowing on one side of the plant only, followed by wilting of the same side. Remove and destroy plants with fusarium wilt. Do not replant tomatoes in that location for 3 to 4 years.

Wilty Plant with Green Leaves

A plant that wilts during the day but recovers overnight is suffering from heat stress or insufficient water. Increase irrigation to 2 inches per week and add 2 inches of mulch. A plant that wilts and does not recover overnight may have bacterial wilt (Ralstonia solanacearum), confirmed by cutting the stem and suspending it in a glass of water. Milky white bacterial ooze streaming from the cut end within 5 minutes confirms the diagnosis. There is no cure. Remove and destroy the plant immediately. Bacterial wilt persists in the soil for 2 to 5 years. Rotate to non-solanaceous crops for that period.

Hornworms

Tomato hornworms (Manduca quinquemaculata) are 3 to 4-inch green caterpillars that strip leaves from stems overnight. A single hornworm consumes 1 square foot of foliage per day. Hand-pick them in early morning when they are visible on the upper parts of the plant. Look for their dark droppings (frass) on leaves below the feeding area. If you find a hornworm covered with white rice-like cocoons, leave it alone. The cocoons are pupae of the braconid wasp (Cotesia congregata), a parasitoid that kills the hornworm and produces 150 to 200 wasps that parasitize other hornworms in your garden. Bacillus thuringiensis (Bt, sold as Dipel or Thuricide) applied to foliage kills hornworms under 1 inch in length but is less effective against full-grown caterpillars.