Quick answer: To learn how to grow tomatoes in containers start with the right pot size, a loose mix of potting soil, compost and coir, plant after soil is 60 F and your last frost has passed, give 1 cup slow release per 5 gallons, stake or cage at planting, water by weight and feed on a steady schedule. Read on for exact pots, recipes, depths, and timings.
Choose the right container
Pot size by tomato type, with exact gallons and examples
Pick the pot size by the tomato type. Use these clear rules.
- Small determinate or patio types: 5 gallon pot, about 12 to 14 inches wide and 12 inches deep. Example, a 5 gallon nursery bucket or a commercial 12 inch patio planter.
- Larger determinate or compact indeterminate: 10 gallon pot, 16 to 18 inches wide and 14 to 16 inches deep. Good for Celebrity or Bush Early Girl.
- Full size indeterminate: 15 to 20 gallon pot, 18 to 24 inches wide and 18 to 24 inches deep. Use for Sungold, Brandywine, or any vigorous slicer you want to grow to full size.
A common mistake is underpotting an indeterminate, then blaming the variety. I lost plants when I tried a large vine in a 5 gallon bucket. Match plant vigor to pot gallons.
Material choices, pros and cons of plastic, fabric, and clay pots
- Plastic: Lightweight, holds moisture, stays cooler than clay in sun. Use for balconies where weight matters. Choose UV rated pots.
- Fabric grow bags: Excellent root air pruning, warm faster in spring, drain well. They dry faster, so expect more frequent watering in heat.
- Unglazed clay: Breathable and pretty, but heavier and will dry faster. Not ideal for very sunny or windy balconies unless you want to water more often.
Drainage, saucer use, and placement for sun and wind
All containers need holes. Drill more if you are unsure. Use a saucer to catch run off on patios, but tip or empty the saucer after 20 to 30 minutes so roots do not sit in cold water.
- Place pots where they get 6 to 8 hours of direct sun. Morning sun is best. In zones hotter than 7, some afternoon shade helps in July and August.
- Protect pots from strong wind which dries leaves and can stress stems. Move pots closer to a wall or use windbreak lattice if needed.
Pick tomato varieties that do well in containers
Determinate versus indeterminate, how many plants per pot for each type
- Determinate: Bush habit, stop growing at a set height, good single season harvest. Plant one determinate per 5 gallon pot, up to two per 10 gallon, or up to three in a 15 to 20 gallon if you space them 10 to 12 inches apart.
- Indeterminate: Vining, keep growing and fruiting. Plant one indeterminate per 10 gallon at minimum. Prefer 15 to 20 gallon for a single plant to reach full yield.
Compact varieties to buy now
These reliably fit containers. I recommend starting with named varieties so you know what to expect.
- Patio
- Celebrity
- Bush Early Girl
- Better Bush
- Tiny Tim (very small, fits 2 to a 5 gallon)
- Sunsugar
- Sweet Million
Heat tolerant varieties for warmer zones, short season picks for colder zones
- Warmer zones (zones 8 and warmer): Heat setters like Solar Fire, Florida 91, Phoenix keep setting fruit at high temps.
- Colder zones (zone 6 and colder): Choose early maturing types, for example Early Girl, Stupice, or Patio. Start seedlings indoors 6 weeks before last frost and transplant when soil is 60 F.
Potting mix and exact soil recipe
Mix by volume
Mix by volume so you can fill a pot the same day. Use clean components.
- 2 parts high quality potting mix, not garden soil. Example: 2 gallons potting mix for a 5 gallon pot.
- 1 part coarse finished compost, for a 5 gallon pot use 1 gallon compost.
- 1 part coconut coir or sphagnum peat, for a 5 gallon pot use 1 gallon coir or peat.
- Add 1 cup of slow release granular fertilizer per 5 gallons of final mix. Work into the top third only.
So for one 5 gallon pot, mix 2 gallons potting mix, 1 gallon compost, 1 gallon coir, and 1 cup slow release fertilizer. Scale up for 10 and 15 gallon pots.
pH target, how to test and correct with lime or sulfur
Tomatoes prefer pH 6.0 to 6.8. Test with a soil pH meter or send a sample to your county extension.
- To raise pH, add dolomitic lime, about 1 tablespoon per 5 gallon pot mixed into the potting media before planting.
- To lower pH, add elemental sulfur sparingly, about 1/2 teaspoon per 5 gallon pot, mix in and retest after 6 weeks. Sulfur acts slowly.
When in doubt, test. Overcorrecting pH in a small container is a common cause of nutrient problems.
When to use inoculants or mycorrhizae
Mycorrhizae help root establishment in new or soilless mixes. Apply at planting if you start from bare root or bare soil blocks.
- Use mycorrhizal powder, 1/4 teaspoon per transplant, dust lightly on roots before covering.
- Use bacterial inoculants if reusing old mix to help with nutrient cycling, follow package rates closely.
Planting, spacing, and timing tied to frost dates
How deep to plant transplants, remove lower leaves, bury stem up to first true leaves
Plant deep. Remove the lowest 3 to 4 inches of leaves, leaving the top foliage intact. Lay the plant on its side in the planting hole and bury the stem up to the first set of true leaves. This encourages extra roots on the buried stem.
Number of plants per container, spacing inches for multi plant planters
- 5 gallon: one small determinate or two Tiny Tim seedlings if you want multiple. Space 8 to 10 inches if two.
- 10 gallon: one mid sized determinate or one compact indeterminate, or two small determinate spaced at 10 to 12 inches.
- 15 to 20 gallon: one full indeterminate, or two smaller determinate spaced at 12 inches.
Timing, safe transplant temperature, tie to last frost date and soil temp of 60 F
Transplant tomatoes after your last frost date and when the soil temperature is at least 60 F. Nighttime air temps should be above 50 F for best growth.
Use these adjustments by zone:
- Zone 5 and colder, start indoors 6 to 8 weeks before last frost, transplant 1 to 2 weeks after last frost when soil is 60 F.
- Zone 6 (central Ohio), start indoors 6 weeks before last frost, move out when soil reaches 60 F and nights are above 50 F.
- Warm zones 8 and up can plant outdoors earlier if night temps are consistently above 50 F, but watch heat stress in midsummer.
| Pot Size | Plants | When to Plant |
|---|---|---|
| 5 gallon | 1 small determinate | After soil 60 F, nights >50 F |
| 10 gallon | 1 compact indeterminate or 2 small determinates | After last frost + soil 60 F |
| 15 to 20 gallon | 1 full indeterminate | After last frost, best yields in full sun |
Staking and support for container tomatoes
Cage sizes and heights, 18 inch cages for determinate, 5 to 6 foot cages or single stakes for indeterminate
- Determinate: 18 inch diameter, 18 inch tall cage is fine.
- Indeterminate: 5 to 6 foot tall cage or a single 8 foot stake driven into the potting mix to the bottom of the pot for stability.
How to install supports at planting, tying and pruning for one or two stems
Install supports at planting so you do not disturb roots later. For stakes drive them into the pot center until secure. For cages set the cage over the plant and press down to firm the soil.
- Tie stems to stakes with soft garden twine or cloth strips every 10 to 12 inches of growth.
- Prune indeterminate to one or two stems by removing side shoots up to the first flower cluster for a single leader. For two stems, leave one sucker below the first flower cluster and train both up supports.
Balcony friendly options, attachable trellis and space saving tips
- Use railing planters with a vertical trellis attached. Pick compact varieties so the plant does not outgrow the balcony.
- Mount lightweight spiral stakes to save space and keep fruit off the floor. Secure pots so wind does not tip them over.
Watering rhythm, deep watering, and heat stress care
How much water per pot, measured in cups or liters per gallon pot size
Measure water by volume to get consistent results. These are starting points, increase in heat.
- 5 gallon pot: 1 to 2 quarts per watering, about 4 to 8 cups.
- 10 gallon pot: 2 to 4 quarts per watering, about 8 to 16 cups.
- 15 to 20 gallon pot: 3 to 6 quarts per watering, about 12 to 24 cups.
In hot weather increase each amount by 25 to 50 percent and check weight after watering to learn your pot’s dry and wet feel.
Frequency rules, morning watering, soak then let surface dry, quick check by weight
- Water in the morning. Soak thoroughly until water runs from drainage holes, then let the top 1 to 2 inches dry before the next deep soak.
- Check by lifting the pot. A fully watered 10 gallon pot feels noticeably heavier than a dry one. Weight check beats a schedule.
Midsummer heat tips, shading, mulching, signs of heat stress and how to cool plants
In July watch for heat stress. Leaves wilting mid afternoon, flowers dropping, and sunscald on fruit are common.
- Provide 30 percent shade cloth in afternoon sun when temps are above 90 F for a week long heat wave.
- Mulch with 1 to 2 inches of straw or shredded leaves to slow surface drying.
- Move pots to a spot with morning sun and afternoon shade if you can. A temporary shade umbrella over pots works too.
Feeding schedule, when and what to feed
Starter feed at planting, example 1 tablespoon balanced soluble fertilizer per gallon of water for first week
Give a starter feed right after transplanting. Mix 1 tablespoon of a balanced soluble fertilizer like 10 10 10 into 1 gallon of water and water each 5 gallon pot with 1 pint of that solution, or water larger pots with proportionally more.
Ongoing schedule, feed weekly with 10-10-10 at labeled rate or every two weeks with a bloom fruit formula like 5-10-10, plus side dress instructions
Use one of these two reliable schedules.
- Weekly soluble method: Feed once a week with a balanced soluble fertilizer at label rate, reducing strength to half if leaves scorch. Water first, then feed.
- Granular slow release + side dress: At planting add 1 cup slow release per 5 gallons. Then every 3 weeks side dress with 1 tablespoon of granular 10 10 10 worked into the top 1 inch of soil around each plant for a 5 gallon pot. Increase to 2 to 3 tablespoons for 15 to 20 gallon pots.
Switch to a bloom formula 5 10 10 at fruit set if you want more fruit development and less vegetative growth. Feed every two weeks, following label. Stop heavy feeding two weeks before final harvest to improve flavor.
Common failure mode, blossom end rot, comes from uneven watering and calcium shortage. Keep water steady, use mulch, and side dress with calcium nitrate at 1 teaspoon per gallon for a short corrective treatment if you see small brown spots on the blossom end.
FAQ heading
Can I grow multiple tomatoes in one large pot?
Yes, but space them. In a 15 to 20 gallon pot you can grow up to two small determinate varieties spaced 10 to 12 inches apart. For indeterminate vines plan one plant per 15 to 20 gallon pot to avoid root competition and poor yields.
How do I know when the soil is 60 F?
Use a soil thermometer pushed into the potting mix 3 inches deep in the morning. If it reads 60 F or higher for several days in a row and night temps are above 50 F, transplant outdoors. County extension offices will also publish local soil temps in spring.
Why are my flowers dropping in July?
Flower drop in midsummer is usually heat related. Day temps above 90 F or nighttime temps above 75 F reduce fruit set. Provide afternoon shade, cool roots with mulch, and keep consistent moisture. Some varieties like Solar Fire are better at setting fruit in heat.
How often should I repot or refresh the soil?
Replace or refresh container media every 2 to 3 years, or sooner if you see salt buildup, poor drainage, or disease. Top dress with fresh compost and replace the top 2 to 4 inches of mix annually for best results.
Is blossom end rot a fertilizer problem?
Blossom end rot is a calcium availability issue triggered by irregular watering or high salts from overfertilizing. Keep water even, stop high nitrogen feeds if present, and use a small calcium nitrate drench, 1 teaspoon per gallon, once or twice as a corrective measure.
