Grow Bag Size vs Number of Plants: A Simple Guide

Two different sized grow bags with handles for easy carrying.

In recent years, fabric grow bags have become popular alternatives to traditional garden beds. They’re sturdy, portable, and made from breathable material suited for growing different types of plants.

Grow bags also come in various sizes. Which, on the one hand, gives you a lot of options. On the other, it presents a problem… 

Which grow bag size is best suited for your plants?

Picking the wrong size can lead to overcrowding. And overcrowding can lead to pests, disease, and unhealthy plants.  

So, I’ve written this guide to help you choose the correct grow bag for your plants. 

Here you’ll find information on,

  • Different grow bag sizes
  • Helpful tips for size selection
  • Grow bag size and plant comparison charts

Because the last I want to see is you spending money on a grow bag that won’t fit your gardening needs.

Guide to Grow Bag Size vs the Number of Plants 

Grow bags are an excellent option for container gardening. 

Like traditional pots, they range in size. And it’s important you select the size appropriate for the number and type of plants you’re growing. 

Choosing the right size will help ensure your plants have enough space to grow properly.

So, let’s look at the sizes and how you can pick one to meet your gardening needs. By the way, if you want to learn about gardening with containers, check out my guide on the subject. You’ll find it helpful.

What Are the Different Grow Bag Sizes

Three grow bags of various sizes.

Grow bag sizes can range from 1 gallon up to 200 gallons. Most people, though, find the 1 – 20 gallon range is sufficient.

For smaller plants such as herbs, a smaller-sized bag will do the trick. 

Larger plants, though, such as peppers or tomatoes, need medium or larger-sized grow bags. The bigger bags will provide more room for these plants to expand and flourish.

But volume isn’t the only feature to consider. Different bags can have different dimensions. Some bags are deeper, while others are wider. 

In general, wide, shallow bags are better for shallow roots, whereas deeper bags are better for plants with larger roots.

And don’t be tempted to simply opt for a large bag. The larger the bag, the more costly it is to fill and the more difficult it is to move around.  

Overall, whether choosing a small, medium, or large grow bag, pick one that provides your plants with enough room to fully grow, but isn’t so large it becomes costly or burdensome.

11 Tips for Choosing Your Grow Bag Size

As a rule of thumb, if you can plant it in a container, you can plant it in a grow bag – assuming the grow bag is the right size.  Here are a few handy tips when picking your grow bag.

1. Take into account the number of plants you’re growing per bag and the root depth of each plant. 

2. Check the seed packet or research the plant, to find out the root depth.

3. Grow bags need to be large enough to accommodate fully grown roots.

4. Check the bag’s dimensions. A grow bag may be wide enough to fit your plant, yet still not be deep enough to accommodate the roots.

5. With most veggies, aim for 5 gallons or larger. Smaller grow bags may not give your plant enough room to grow, especially if you’re growing more than one plant per bag. 

6. Limit smaller bags to one or two small plants, such as small herbs.

7. Shallow-rooted plants like green onions, garlic, or lettuce can be grown in wide, shallow grow bags.

8. Deeper-rooted plants such as carrots, parsnips, or Brussels sprouts require taller bags.

9. Large plants like tomatoes and potatoes, need large, 10 – 20 gallon bags, and only plant one plant per bag.

10. For 20-gallon or larger grow bags, consider planting one large plant in the middle and smaller plants like onions around the edges. Make sure the plants are compatible.

11. If unsure, it’s better to opt for a larger bag than a smaller one. This way you know there will be enough soil and water available for your plants.

If you have further questions about grow bags, take a look at my article that answers the most common grow bag questions

Grow Bag Size and the Number of Plants

Below are two general guides outlining,

  • spacing needs for common vegetables.
  • grow bag sizes vs the number of plants each size can accommodate based on the spacing needs of the plant. 

Remember to check your vegetable’s root depth. The bag may be wide enough for your veggie, but too shallow for its roots.

Spacing NeedsVegetable
2 – 3 inches apartcarrots, garlic, green onion, peas, radishes
4 – 6 inches apartbens, leaf lettuce, beets, kohlrabi, onions, parsnips, spinach
8 – 12 inches apartcabbage, cucumber, collards, head lettuce, swiss chard, peppers
12 – 18 inches apartbroccoli, cauliflower, Brussel sprouts, eggplant, tomatoes, potatoes, kale
Grow Bag
# Of Plants
2″ – 3″ Apart
# Of Plants
4″ – 6″ Apart
# Of Plants
8″ – 12″ Apart
# Of Plants
12″ – 15″ Apart
5 gallon
12″ x 10″
9 vegetables2 vegetables1 vegetableNone
10 gallon
16″ x 12″
16-25 vegetables3-4 vegetables2 vegetables1 vegetable
15 gallon
17.5″ x 15″
25 vegetables4-6 vegetables2 vegetables1 vegetable
20 gallon
20.5″ x 14.5″
36-40 vegetables8-9 vegetables2 vegetables1 vegetable

In the end, picking the right sized grow bag comes down to the plant you’re growing, the space needed between each plant, and the extent of the plant’s root system.

Final Thoughts

  • Grow bags are a great alternative to traditional containers.
  • Grow bags come in various sizes ranging from 1 gallon up to 200 gallons.
  • Grow bags can also have different dimensions.
  • The size of the grow bag should be large enough to accommodate the size of the plant or plants.
  • When choosing a grow bag, consider root depth as well as spacing needs and the width of the plant.

If you enjoyed this article on grow bags vs the number of plants and found it helpful, feel free to share it.


Hi! My name is Angela Carr. I started this site to share my love for plants and gardening. My aim is to provide my readers with easy tips and tricks on plant care, fun facts, and encouragement for the new plant owner or anyone questioning the colour of their thumb!

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