You want to grow tomatoes in containers and the first question is clear: what size grow bag for tomatoes works best. In this guide we will give direct, practical answers you can use today. No fluff. You will learn the recommended bag sizes for different tomato types, how much soil you need, planting and care tips tied to bag size, troubleshooting, and simple yield expectations. Let us get started.
Quick Answer — what size grow bag for tomatoes
For most home gardeners the sweet spot is 10 to 15 gallon grow bags for a single tomato plant.
- Use 5 to 7 gallon bags only for dwarf, patio, or very small cherry varieties.
- Use 15 to 20 gallon bags for large indeterminate plants or when you want maximum yield.
- Use 25+ gallon bags if you plan to grow multiple vigorous indeterminate tomatoes in one container or want a truly large root zone.
Why those numbers? Tomatoes need root volume to access water and nutrients and to avoid stress in hot weather. Bigger bags hold more moisture and feed, which equals steadier production.
Why grow bags work for tomatoes
Benefits of grow bags compared with pots and ground
Grow bags offer several real advantages for tomatoes:
- Air pruning. Fabric bags let roots air prune instead of circling, which creates a denser, healthier root system.
- Better drainage. Excess water escapes, reducing risk of root rot and some soil diseases.
- Portability. You can move bags to chase light or protect plants from extreme weather.
- Space efficiency. Ideal for balconies, patios, and small yards where in-ground planting is not possible.
Limitations to keep in mind
Grow bags also dry faster than the ground, so you will likely water more often. They may heat up in direct, intense sun, so in very hot climates some shade or a lighter colored bag helps.
Key factors that determine what size grow bag for tomatoes
Choosing the right bag is not random. Consider these factors.
Tomato type and growth habit
- Determinate (bushy) varieties stop growing at a certain height. Many determinate types do fine in 10–15 gallon bags.
- Indeterminate (vining) varieties grow all season and need more root space. Aim for 15–20 gallon or larger for best results.
- Dwarf and patio varieties can thrive in 5–7 gallon bags. Cherry tomatoes often do well in smaller bags but will still perform better in 10 gallon bags if you want bigger yields.
Expected yield and root space
Larger bags produce steadier yields because they store more water and nutrients. If you want a heavy producer like a beefsteak or large slicer, choose a 20 gallon bag or larger for single-plant comfort.
Climate and watering needs
In hot, dry climates pick larger bags to buffer daily temperature swings and to reduce how often you must water. In cooler, mild climates smaller bags can work with less risk.
Mobility and space constraints
If you plan to move plants regularly, choose bags with sturdy handles and a size you can manage. A filled 20 gallon bag is heavy. For rooftop or balcony use, check load limits.
Recommended grow bag sizes and exact use cases
Below is a practical breakdown so you can pick the right size quickly.
5–7 gallon grow bags — use case and limits
Best for: dwarf patio tomatoes, tiny cherry varieties, seedlings and temporary setups.
- Plant count: 1 small plant only.
- Soil volume: about 4–6 liters per gallon, so roughly 20–40 liters.
- Pros: light, portable, saves space.
- Cons: dries quickly, lower yield, not ideal for large varieties.
Use when you have very limited space or when growing micro varieties on a windowsill.
10–15 gallon grow bags — the most versatile choice
Best for: most cherry, roma, and compact indeterminate varieties.
- Plant count: 1 full-sized or 1 compact and 1 micro plant in some cases.
- Soil volume: roughly 40–60 liters.
- Pros: good moisture buffer, manageable weight, excellent balance of yield and care.
- Cons: still needs regular watering in hot weather.
This is the go-to recommendation for container tomato growing. If you are not sure, choose a 10 or 15 gallon bag.
15–20 gallon grow bags — for full-size indeterminate plants
Best for: full-size vining tomatoes and growers who want larger yields.
- Plant count: 1 vigorous plant for best results. Two small determinate plants possible with careful management.
- Soil volume: roughly 60–80 liters.
- Pros: large root zone, more stable moisture and nutrients, supports heavier fruit loads.
- Cons: heavier to move, more soil to prepare.
Choose this when you plan for peak production of slicers or beefsteaks.
25+ gallon grow bags — maximum yield and multi-plant setups
Best for: serious container gardeners or small-scale growers who want one big plant or multiple plants in one container.
- Plant count: 1 very large plant or 2 smaller determinate plants.
- Soil volume: 100 liters plus.
- Pros: high yield potential, fewer waterings per day.
- Cons: heavy, needs strong support structure.
Use these when you have space and want the biggest harvest from container-grown tomatoes.
Special case: vertical pocket bags and stackable systems
These work well for cherry tomatoes and multiple small plants. They save ground space but each pocket has limited soil volume, so yields per plant are smaller. They are great for decorative or vertical gardening in tight spaces.
How to prepare a grow bag for tomatoes
Recommended soil mix and amendments
Aim for a light, well draining mix with good organic matter. A reliable recipe:
- 50–60 percent quality potting mix
- 30–40 percent well aged compost or rotted manure
- 10 percent perlite or coa
Add a slow release fertilizer at planting time and plan a feed schedule during fruiting. Test soil pH if possible; tomatoes prefer slightly acidic soil around pH 6.0 to 6.8.
Filling technique and drainage
- Place the bag on a flat, stable surface with good sunlight.
- Fill to about one third with your soil mix when starting seedlings or transplants to give space for top dressing and root growth. For direct planting, fill to within 3 inches of the top.
- Ensure the bag has adequate drainage holes. If moisture pools, lift the bag occasionally to allow free drainage.
Placement for sunlight and microclimate
Tomatoes need 6 to 8 hours of sunlight daily. Morning sun is ideal. Avoid strong afternoon sun in very hot climates or provide partial shade during heatwaves. Place bags where you can easily water and tie supports.
Support systems for grow bags
Use sturdy cages, stakes, or trellises anchored to the ground or to heavy objects. Fabric bags can shift in wind when top heavy, so secure cages to prevent tipping. For indeterminate tomatoes use a tall cage or single-stem trellis.
Planting and early care by bag size
Transplanting seedlings into grow bags
- Harden off seedlings outdoors for a week before planting.
- Plant tomatoes deep by burying a portion of the stem to encourage extra root development. In bags, you can bury up to half the plant if your bag depth allows.
- Space single plants in a bag centrally so roots have equal access to soil.
Initial watering and settling in
Water slowly and deeply at planting so soil settles around roots. Avoid soggy conditions by ensuring excess water drains. For the first week water daily if temperatures are high, then reduce frequency as roots establish.
Mulching and surface management
Add a 1–2 inch layer of organic mulch such as straw, shredded bark, or compost on top of the bag. Mulch helps retain moisture, keeps soil temperature stable, and reduces splashback that can spread soilborne disease.
Ongoing care — watering, fertilizer, pruning
Watering schedule by bag size and climate
- 5–7 gallon: likely daily watering in hot weather.
- 10–15 gallon: every 1 to 3 days depending on heat and rainfall.
- 15–20+ gallon: every 2 to 4 days; less frequent in cool weather.
Check soil moisture by feeling the top 1 to 2 inches. If dry, water thoroughly until some water drains from the base. Avoid frequent shallow watering.
Fertilizer plan
Start with a balanced feed at planting. Once flowering begins, switch to fertilizer higher in potassium and phosphorus to support fruiting. Organic options like compost tea, fish emulsion, or seaweed extract work well. Apply as directed every 2–4 weeks during the main growing season.
Pruning and training
Indeterminate tomatoes benefit from removing some suckers to focus energy on main stems and fruit. For container growing, a single stem trained up a stake or trellis is easiest. Determinate types generally do not need heavy pruning.
Monitoring for stress
Heat stress shows as leaf wilting or sun scald on fruit. Mulch, shade netting, and consistent watering help. Nutrient deficiencies show as yellowing or poor fruit set. Adjust feed and check pH.
Troubleshooting common problems for bag-grown tomatoes
Blossom end rot
Blossom end rot is usually a calcium uptake issue aggravated by inconsistent watering. Keep moisture steady, add calcium if needed, and avoid overfeeding with high nitrogen fertilizers.
Overheating and root stress
Black or brown, mushy roots mean heat or poor drainage. Provide shade in hot afternoons and ensure good soil mix with perlite to prevent compaction. Move bags to cooler spots if possible.
Pests and diseases
Common pests: aphids, whiteflies, hornworms. Use hand removal, insecticidal soap, or neem oil. Common diseases: early blight and late blight. Remove infected foliage, improve airflow, and avoid overhead watering.
Plant outgrows its bag
If a plant becomes root bound or highly stressed, transplant to a larger bag if possible, or prune roots lightly and refresh soil. For indeterminate varieties, consider supporting and feeding rather than transplanting midseason.
Harvesting and realistic yield expectations
When tomatoes are ready
Harvest when fruit reaches full color and firmness for your variety. For best flavor pick slightly ripe tomatoes and allow to finish indoors if needed.
Typical yields by bag size (conservative estimates)
- 5–7 gallon: small harvest, perfect for snacking cherry tomatoes — expect a few pounds over the season.
- 10–15 gallon: reliable single-plant production — expect 10 to 20 pounds depending on variety and care.
- 15–20 gallon: better yields for large varieties — 15 to 30 pounds per plant is possible with good management.
- 25+ gallon: high production potential, especially for large indeterminate varieties.
Actual yield depends on variety, climate, and care.
Post-harvest and end of season
After harvest remove plant debris to reduce disease carryover. Refill or refresh soil and consider rotating to different crops next season.
Buyer checklist — what to look for in a tomato grow bag
When you shop select bags with these features:
- Material: durable felt or heavy non-woven fabric, UV resistant.
- Thickness: thicker fabric lasts multiple seasons.
- Handles: reinforced handles make moving easier.
- Drainage: good breathability and drainage holes or woven sides.
- Reusability: washable and refillable for multiple seasons.
- Size options: clear marking of gallon capacity and dimensions.
If you plan bulk planting, choose bags with consistent size and sturdy construction.
Conclusion
Now you know exactly what size grow bag for tomatoes to choose based on variety, space, and goal. For most gardeners a 10 to 15 gallon bag is the best starting point. If you want larger plants and increased yield go to 15 to 20 gallons. If space is tight or you only want small snack tomatoes use 5 to 7 gallons.
We are a grow bag manufacturer and we make durable, breathable grow bags in sizes from 5 gallons up to 30 gallons. If you want custom sizes, reinforced handles, UV resistant fabric, or bulk orders for a garden project we can help. Contact us for samples or a quote and let us help you pick the perfect grow bag for your tomatoes and space.
If you want, tell us your tomato variety and available space and we will recommend the exact bag size and soil mix for your situation.
FAQs
What size grow bag for cherry tomatoes?
For cherry tomatoes a 10 gallon bag is the sweet spot. You can use 5 gallon bags for compact cherries but yields will be lower.
How many tomato plants per grow bag?
One plant per bag is safest for 10–20 gallon sizes. You can fit two small determinate plants into a very large 25+ gallon bag but expect more maintenance.
How much soil for a 10 gallon grow bag for tomatoes?
A 10 gallon bag typically needs about 25 to 35 liters of potting mix depending on bag depth. Measure bag volume or fill by weight calculations if you need precision.
Can I grow tomatoes in a 5 gallon grow bag?
Yes, for dwarf or small cherry varieties. Expect smaller yields and more frequent watering.
What size grow bag for tomatoes in hot climates or zone 9a?
In hot zones choose larger bags like 15–20 gallons to buffer heat and reduce watering frequency. Provide afternoon shade during heat waves.
How often should I water tomatoes in a grow bag?
Water when the top 1 to 2 inches of soil are dry. That may be daily in hot months for small bags and every 2 to 4 days for larger bags.
Are grow bags better than pots for tomatoes?
Grow bags have advantages in root health and drainage but require closer watering attention. For most container growers they outperform plastic pots over time.
How long do grow bags last and can they be reused?
High quality fabric grow bags last 3 to 5 seasons with proper care. Clean, air dry, and store them when not in use to extend life.