Growing tomatoes in 5 gallon buckets is one of the most common ways renters and small space gardeners grow their own. It also fails more often than it should. Most of the time the reasons are predictable.
Grow bags work on the same principle with one key material difference. Fabric breathes, plastic does not, and that changes how often you need to show up with a watering can.
This guide covers container size, drainage, soil, watering, and feeding using university extension guidance. It also covers where real gardeners say buckets and bags actually go wrong.
The short version
Five gallons is the practical floor, not the ideal. It works well for a determinate variety and works poorly for a sprawling indeterminate one.
Buy or use a soilless potting mix, never garden soil, and drill extra drainage. Water daily in hot weather, and feed every couple of weeks since nutrients wash out of containers fast.
Bigger is safer than smaller if you have the choice. A tipped over plant in July is the most common bucket failure.
How big does the container actually need to be?
University of Maryland Extension sets the floor at 2 gallons for cherry tomatoes and 5 gallons for standard varieties. The same guidance adds that yield keeps climbing as container size increases beyond that minimum.
There’s a sharper line worth drawing, though. Five gallons works for determinate, or bush, varieties. Indeterminate varieties keep growing all season, so the root system needs more room to match all that extra vine.
The UC Master Gardener Program of Contra Costa County recommends 18 to 24 inches of depth for the best results. Some varieties are fine at five gallons, while others need more than double that soil volume. One experienced grower on a Houzz forum thread put it bluntly: determinate types only in a 5 gallon bucket, or the plant gets top heavy and tips.
Grow bags vs buckets: what actually differs
A plastic bucket holds water and air exactly where you put them. A fabric grow bag does not, since the material itself breathes.
That has one proven, physical consequence. Grow bags dry out faster than a sealed bucket. They need more frequent watering, especially in wind or full sun.
Fabric bags also get credit for encouraging air pruning. That is a root growth pattern where roots stop circling and branch out instead when they hit open air at the fabric wall. The claim comes from an extension source, so it is worth taking seriously.
A head to head yield trial comparing bags and buckets specifically for tomatoes is still hard to find, though. Treat bigger harvest promises from grow bag sellers with some skepticism until better data exists.
Drainage: buckets need holes, and placement matters
Every container needs drainage, full stop. A bucket with no holes drilled is a slow motion root rot waiting to happen.
For small buckets, drill several holes in the bottom. A different trick works for larger containers. Place some drainage holes a few inches up the sides instead of only at the bottom, which creates a small water reservoir the roots can still reach.
That reservoir trick is close to the idea behind self watering buckets, just simplified. A fuller version of the same idea uses a wicking basket suspended in an inner bucket, with a PVC pipe reservoir and a drainage hole positioned to prevent overflow.
Soil: skip the garden dirt
Garden soil compacts hard in a container and drains poorly once it does. Every extension source reviewed for this guide says the same thing: use a soilless potting mix instead.
The UC Master Gardener Program notes that quality potting mixes often include coir specifically to hold moisture while still draining well. A specific tip for calcium: mix in roughly one cup of garden lime per 5 gallon container.
Calcium availability affects blossom end rot risk in containers just as it does in the ground. That one cup of lime is a small step against a common problem.
Watering: the real time commitment
Containers dry out faster than garden soil, and that is the tradeoff for the convenience. The UC Master Gardener Program warns that a full sun container may need water once a day. Heat waves or wind can push that to twice a day.
Skip the fixed schedule and use a simple test. Push a finger into the soil, and water again only once it no longer feels moist.
A self watering bucket setup exists specifically to reduce this burden. One experienced Houzz forum grower recommended exactly that approach to avoid watering twice a day through late July.
Feeding: containers need more, not less
Potting mix runs out of nutrients faster than garden soil, since every watering flushes some away. Light fertilizing every two weeks suits long season crops like tomatoes. That keeps a continuous harvest going.
A gardener who documented a full season of grow bag results on Garden.org found this out the hard way. Heavy nitrogen inputs early in the season, without balanced potassium and phosphorus later, led to lush plants. Those plants underperformed on actual fruit.
What actually goes wrong
Overcrowding is the most common mistake in the same forum account. Packing too many plants into a shared trough or bag competes for the same limited root volume and starves everyone.
Tipping is the second most common problem, especially with taller indeterminate varieties in a narrow 5 gallon bucket. A sturdy stake driven through the drainage layer before filling with soil heads off most of that risk.
Uneven feeding rounds out the list. Rich soil early and a bloom formula switched too late in the season shorted one grower’s plants. The nutrients fruit needs to size up simply arrived too late.
Frequently asked questions
Is a 5 gallon bucket big enough for a tomato plant?
Yes for a determinate, or bush, variety. Indeterminate varieties generally perform better in something larger, since their root systems keep expanding all season alongside the vine.
Do grow bags need more water than buckets?
Yes. Fabric breathes and dries out faster than a sealed plastic bucket. Grow bags typically need more frequent watering, especially in wind or hot sun.
What soil should I use in a bucket or grow bag?
A soilless potting mix, not garden soil. Garden soil compacts in containers and drains poorly, while potting mixes are formulated to hold moisture and still drain well.
How often should I water tomatoes in containers?
Often daily in full sun, and possibly twice a day during heat waves. A simple finger test, watering once the top inch no longer feels moist, works better than a fixed schedule.
Why did my bucket tomato tip over?
Usually a mix of a tall indeterminate variety and a narrow container. Stake the plant early, and consider a bigger container or a determinate variety next season if tipping is a recurring problem.
The bottom line: growing tomatoes in 5 gallon buckets works reliably for determinate varieties with the right soil, drainage, and watering routine. Indeterminate types generally need more room. See our how to grow tomatoes in pots guide for the broader container growing guide, and our how to fertilize tomatoes guide for a full feeding schedule once the plant is in.
SOURCES
University of Maryland Extension: Growing Vegetables in Containers and Salad Tables. https://extension.umd.edu/resource/growing-vegetables-containers-and-salad-tables
University of Wisconsin Extension, Marinette County: Growing a Tomato Plant in a Container. https://marinette.extension.wisc.edu/files/2018/01/tomato-in-a-container_sr.pdf
University of California Agriculture and Natural Resources, UC Master Gardener Program of Contra Costa County: Growing Tomatoes in Containers. https://ucanr.edu/site/uc-master-gardener-program-contra-costa-county/article/growing-tomatoes-containers
University of Florida IFAS Extension, Leon County and FAMU Cooperative Extension: Self Watering Bucket Instructions. https://sfyl.ifas.ufl.edu/media/sfylifasufledu/leon/UF-IFAS-Leon-County-and-FAMU-Cooperative-Extension-Self-Watering-Bucket-Instructions.pdf