What Size Grow Bag For Tomatoes?

Last updated: 9/11/2020

Are you worried about finding the right size grow bag for your tomatoes?

I found myself in that situation a few days ago when I wanted to put every space in my small garden into best use. I decided to grow tomatoes in bags. 

I didn’t know too much about growing tomatoes, which got me worried about what size grow bag for tomatoes to use.

My situation provoked me to find tomato growers in my neighborhood. 

With additional in-depth research, I learned more than I expected. 

I used a 5-gallon bag for miniature tomatoes. Most tomato varieties will grow well in 5 to 10-gallon bags.

If you are planning to grow tomatoes in bags, you found the right place. 

Without further ado, let’s di​g in.

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Why Use Grow Bags For Growing Tomatoes

If you are a casual gardener or a serious greenhouse grower, you will want to use the best bag for your tomato growing. This is why you need grow bags.

Grow Bags Encourage Excellent Airflow

They allow more contact between soil and air. 

This encourages better aeration, preventing compaction. 

As a result, your plants will easily absorb nutrients from the soil.

Stronger Root Systems

Grow bags allow the root-pruning of your tomatoes. 

This means, when the roots grow to the edge of your bag, they don’t circle up. Instead, they stop growing farther. 

Then, your tomatoes sprout newer roots along the tap. 

This makes your tomato roots grow healthier and more robust in the grow bags.

They Are Convenient

You can use grow bags to grow tomatoes quickly. 

Most of them come with handles, making it easier to move them to different locations. 

It is also easier to fix your handles if they don’t come with any.

Additionally, you can use the handles, with a rope or chain, to hang your grow bag for indoor or outdoor use.

Grow Bags Are Affordable Compared To Commercial Grow Containers

Most people who opt for containers think more about decorating their backyard or doing gardening as a hobby.

grow bag for tomatoes

Still, you can use grow bags for the best results from your efforts. 

Grow bags come in a variety of elegant colors and at affordable prices compared to containers.

They Allow Better Drainage

Grow bags are the best when it comes to watering your tomatoes. You don’t need to worry about over watering. 

Together, with the drainage holes, their porous nature will allow excess water to flow out of the grow bag.

Grow bags also allow more contact between soil and air. This encourages water to escape into the atmosphere by evaporation.

Can Be Used Anywhere With The Right Soil

You can easily carry a grow bag to any location you want. 

You can also use these bags for growing your potatoes in a limited space, such as your rented home.

Grow bags also put you in a better position for your gardening ambitions. 

You can prepare your best soil, pack it into grow bags, and use them in any place, including those with poor soils.

You Can Make Your Own Custom Grow Bag

Grow bags do not limit DIY enthusiasts. 

If you also enjoy DIY, you can easily make your custom grow bag from plastic or fabric. Fabric is more breathable than the former.

Grow Bags Vs. Traditional Containers Or Pots

Healthier Roots With Grow Bags

Roots never stop growing in pots.  

When they reach the container’s edge, they continue growing in search of more water and nutrients. This leads to the roots encircling in the pot. 

As a result, the roots become constricted, making them take in less water and nutrients. 

Additionally, the stem becomes compressed, eventually damaging your plant structure.

On the other hand, grow bags prevent this issue by encouraging root-pruning. 

When the roots reach the edge of the grow bag, they sense drier soil. 

Instead of continuing to grow, they stop and instead, newer roots emerge from another point of the taproot.

The more fibrous root system in tomatoes grown in grow bags, means more water and nutrient intake.

Grow Bags Are Easier To Store

You can store grow bags more easily than traditional containers. This might be a great advantage during the off-season if you use grow bags

Traditional pots will require a lot of space if you have to store them. 

With the grow bags, you will only need to empty them, they fold easily, and keep them, even in a limited space.

Traditional Pots Require Careful Watering

Some planters may complain of excess water demand by the grow bags, compared to pots, when it comes to watering. 

best size for grow bag

If this is the case, check on the type of soil you are using. 

The best soil for grow bags will demand relatively more water than containers.  

On top of that, you can easily over water when using pots. 

Unlike the porous grow bags, pots depend on the holes you make to let out excess moisture. 

These holes can be less than enough, leading to excess water in the pots. 

This may cause your pants to drown, and eventually cause mold and fungus build-up.

Grow Bags Are Versatile

You might find working with grow bags fun. 

They are lightweight and most come with handles, which make it easy to move them to any location you want.

With their biodegradable nature, you can plant your grow bags directly in the ground. 

That means you can take advantage of their biodegradable nature and start your plants early in the season. 

This can be a wise decision, especially if you live in a climate having a short growing season.

​How can you do that?

You can use the bags to start your seedlings indoors during the winter.  

Use grow lights to provide enough light for the young plants. 

When the planting season comes, you can transplant your plants with the grow bags outdoors.  

Best Soil For Grow Bags

You can use the ordinary soil used for most containers, but you can opt to prepare the soil yourself using various mixtures for the best results. 

You might find this mix of soil the best, especially if you use a fabric grow bag.

Get moss, compost mixture such as mushroom, and vermiculite to prepare your soil mix. 

Ensure to add one-third of each of these components in every bag.

Alternatively, you can obtain or order the best soil for your grow bag from a credible gardening store. 

Here you can find soil specifically mixed for growing tomatoes. 

Most of these mixtures contain soil, perlite, moss, peat, and natural compost.

Tips For Growing Tomatoes In Grow Bags

Intense preparation eases your work. 

As if the information I have given you is not enough, I will take you through some tips to help you get the best out of your efforts in tomato growing.


Proper watering is a vital exercise when growing tomatoes in grow bags. 

With a few people complaining about using excess water when using grow bags, here is a solution.

  • Use the correct soil mixture for your grow bag. We previously looked at this in detail. The vermiculite in the soil mixture helps in holding water.
  • Use a growing ring. Push the ring into your compost before you plant the tomatoes. Add more peat-free compost to the grow ring then plant your tomato plant.
  • Mulch. Mulching slows down evaporation keeping the water in the soil for your plants.

Tips For Proper Watering

1. Water Slowly

Tomatoes are fragile. Use water under low-pressure when watering. 

The best method you can apply here is the drip irrigation method. 

Use your drip hose to water your tomato plants slowly. 

This ensures water uniformly and deeply penetrates the roots without breaking the stalk or disturbing the soil texture.

2. Concentrate On The Roots

Watering from above is usually discouraged in most crops to avoid wasting water. 

When it comes to tomatoes, they carry more weight. It is recommended to water directly at the base of the stock. 

This kind of watering will discourage the attack of disease and pests.

3. Water Regularly

There is no rule to how often you should water your tomato plants. You need to be careful about the weather and if your plants are actively growing. 

If your plants are indoors, remember they will entirely depend on your watering. This will require more watering than those grown outdoors.

More water will be required during the growing stage. 

When they begin producing fruits, you should slightly reduce watering. 

This will make the plant concentrate on producing more fruits and ripening them, rather than producing new foliage. 

Too much water in the fruition period also makes the fruits watery and tasteless.

Other factors to consider in watering your tomatoes include: 

  • The size of the plant 
  • The type of soil
  • Prevailing temperatures and humidity
  • Amount of fruits
  • State of the fruits
watering tomato plants

Improper watering

Although your chances of over watering in grow bags are minimal, problems may arise from improper watering. 

How will you know if you are doing it the wrong way? 

Below are pointers to help you check on your watering habits:

  • Stunted growth
  • Blossom end rot
  • Low quality fruit
  • Root rot which causes root loss
  • Reduced fruit production
  • Leaf roll
  • Your plants become susceptible to pests


Enough fertilizer is essential for faster growth, quantity and quality of fruits. Tomatoes in grow bags require regular watering. 

This leaches nutrients out of your grow bags. If you are not vigilant enough to include fertilizer in the grow bags, your plants will be deprived.

Tips For Fertilizing Tomatoes In Grow Bags

1. Before Planting

If you want to plant tomato seeds, you may not need to apply fertilizer at the planting stage. 

When you are sure you have the right soil with good nutrient composition, the seed’s nutrients are enough to germinate.

However, you can mix the soil with organic fertilizer. 

When inorganic fertilizers come into contact with the seeds, they may burn out the seeds,

2. Seedling Stage

If you opt to use seedlings for your grow bags, you will have to remember to fertilize them.

Your tomatoes need enough fertilizer to speed up growing dense foliage and strengthen the stalk at this stage.

The most appropriate nutrients required at this stage include

  • Nitrogen, which helps in the continuous growth of leaves and branches.
  • Potassium, to aid photosynthesis and continuous growth of your plants. Potassium also strengthens the plant making it less susceptible to some common diseases.
  • Calcium, which is essential for root growth. It also helps in leaf growth and producing firm tomato fruits.

3. Full-Grown Plants

This stage requires careful examination of your plants to know the most appropriate fertilizer to apply. 

Not every fertilizer will be useful. Some may also do your plant more harm than good.

These are the most appropriate fertilizer nutrients required at this stage:

  • Phosphorous, the primary nutrient your tomatoes will require at this stage. This nutrient is excellent in aiding fruit development. Your plants will also utilize these nutrients in fighting stress.
  • Nitrogen – Another nutrient fantastic for your plants at this stage is nitrogen. Nitrogen helps in the growth of foliage. Remember to apply this nutrient in small amounts, as too much may lessen fruit production.
  • Magnesium. When you realize your tomatoes are about to start producing flowers, apply fertilizer rich in this nutrient. Magnesium is good for keeping your tomato plants green, improving flowering as well as the fruit quality.
  • Boron and zinc are micronutrients essential for the last stage of your tomato development. They help in the flowering and ripening of tomato fruits.

Best Tomato Fertilizers

We have already talked about the macro-nutrients and micro-nutrients necessary for each stage of your tomato growth. 

Here are some of the best fertilizers with these nutrients.

Natural Fertilizer

  • Compost is the best pure organic fertilizer you can use. It is rich in macro-nutrients and micro-nutrients, which are released gradually throughout the growing season.
  • Fish emulsion.This is mainly rich in nitrogen, phosphorus, potassium, calcium, sulfur, and magnesium.
  • Organic cottonseed meal. This contains nitrogen, phosphorus, and potassium in a ratio of about 6:2:1.Organic cottonseed meal also contains calcium, magnesium, copper.

Artificial Fertilizers With NPK Ratios

  • Jobe’s Organics 9026 Fertilizer. 2-5-3
  • Miracle-Gro Water soluble. 18-18-21
  • Dr. Earth Organic 5tomato, Vegetable, and Herb Fertilizer. 4-6-3
  • Tomato-Tone Organic Fertilizer. 3-4-6
  • Greenway Biotech Water Soluble Tomato Fertilizer. 4-18-38

Disease And Pest Prevention

Disease and pests bring the most challenging test for any tomato planter. Most people who fail the test miss out on a few prevention tips. 

Otherwise, everyone could be smiling every season. This is an opportunity for you to take measures to prevent pests and diseases. 

Tips For Pest And Disease Prevention

  1. Determine the common pest and disease pressures in your area. Then select the resistant varieties.
  2. Choose to grow varieties adapted to a grow bag environment.
  3. Adapt best cultural practices such as proper watering, avoid working on your tomatoes when the leaves are wet, and maintain good hygiene to create a healthy environment for your tomatoes.
  4.   Scout your tomatoes routinely. Pinch off any leaves that show signs of disease and dispose of them immediately.
  5. Get rid of dead tomato plant debris.
  6. Practice mulching.
  7. Disinfect tomato grow bags before using them.

To be aware of pests and diseases to control, check out these categories below.

Tomato Disease

  • Foliar tomato diseases – These diseases affect the leaves and the fruits. They include: a bacterial speck, early blight, late blight, gray leaf spot, and powdery mildew.
  • Seed borne diseases – You can prevent these diseases by planting well-treated seeds. Insist on getting your tomato seeds from a reputable source. These diseases include: bacterial spot and bacterial canker
  • Stem diseases – Affects not only the stem but also the leaves and even the fruits. They include Alternaria stem canker and Damping off.
  • Soil-borne disease of tomato – These diseases affect the plant through the roots. Most cases happen when you repeat planting tomatoes on the same soil in different seasons. They include: bacterial wilt, root rot, Fusarium wilt, and cocky root rot.
  • Tomato viruses – For these viruses to spread, they need a carrier. Proper hygiene in handling your tomatoes and grow bags is necessary. These viral diseases include: tomato apex necrosis virus, tomato yellow leaf curl virus, Pepino mosaic virus, and tomato spotted wilt virus.

Tomato pests

These pests include:

  • ​Aphids
  • Hornworms 
  • Whiteflies 
  • Tomato psyllids 
  • Thrips
  • Tomato fruit worms​ 
  • Potato flea beetles
  • Nematodes such as the root-knot nematodes
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Final Thoughts

With much having been said about grow bags for your tomatoes, it is time to try it out practically. 

Get the most appropriate tomato variety in your place, the best grow bag size (you can go for the 5-gallon grow bag), the best soil for the grow bag, and get started.  

Don’t be troubled about the right size grow bag for tomatoes as I did!

Related Questions

1. Do Tomatoes Grow Better In Pots Or In The Ground?

Growing tomatoes in pots is more manageable. 

Pots or grow bags give you a chance to start your tomatoes early. This way, your tomatoes can escape some diseases and pests. 

You can also tell what kind of nutrients your plants need at a particular stage of growth.

Although growing tomatoes in pots require close attention, it is easy to manage your plants’ overall health.

2. Can You Plant Tomatoes In A 5-Gallon Bucket?

The size of the bucket depends on the variety of your tomatoes. Wider tomato varieties will require a bigger sized bucket. 

Nevertheless, a 5-gallon bucket is perfect for most tomato varieties.

 If you are not sure about the sizes, use a single 5-gallon bucket for every tomato plant.

Green Thumb Gardener
grow bags for tomatoes
Jeremy Starke

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