How to use a growbag properly

How To Use A Growbag Properly!

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One of my readers asked for some help with their growbags and if I could write an article on how to use them correctly, so here it is! If you have anything specific you need help with, then just let me know, and I will help you out.


A lot of growbags often have printed squares on the front showing you where to cut out. These Growmoor tomato planters don’t, but I have drawn them on, so you can get an idea of what I mean below.

They often have squares marked on to cut out
They often have squares marked on to cut out.

These squares are to show you where to cut out. They are only guidelines, you can cut out your holes however you like.

On a large, deep growbag like this, I usually go for three tomato plants. On smaller bags, you are better off sticking to two plants.

Cut out squares in the plastic
Cut out squares in the plastic.

Cutting holes in the plastic is simple enough. It’s only thin, so any sharp object will do. As I often seem to forget to take my gardening knife to the allotment, I seem to end up using my secateurs more than anything.

The Plant Pot Method

Now you could plant directly into this hole, which will work fine. But there is a straightforward thing you can do to improve your grow bag.

That is, using a pot on top of the growbag to increase the depth. This is great for plants like tomatoes that love having their roots nice and deep.

It also helps increase water retention, meaning you don’t need to water your plants just as often.

Get A Plastic Pot
Get A Plastic Pot

Take a large plastic plant pot and cut the bottom out of it so it is more of a sleeve. I had to use my secateurs again so it looks like a bit of a dog’s dinner, but it will still work!

Cut The Bottom Out
Cut The Bottom Out

Then fill the pot up with compost and you now have a really nice, deep area in which to plant your tomatoes into.

Put In The Cutout And Fill With Compost
Put In The Cutout And Fill it With Compost

The Half And Half Method

Another common way people use their grow bags is to cut them in half. You made one cut right in the middle just through the top of the bag.

Cut in half down the middle
Cut in half down the middle.

you can then stand the bag up as below.

Stood up half grow bag
Stood up half grow bag

This allows you to have two really deep planters to grow in. The downside is that this limits you to two plants whereas you can get three in a large grow bag using the pots method.

How to use a growbag properly
How to use a growbag properly

Which Is Best?

It’s hard to say, really, which is why I’m going to test it out this year. I will grow tomatoes in both of these growbags this year.

Three plants using the pot method and then two in the half and half method. I will measure the production and see whether two plants with lots of soil to grow into actually end up more productive than three squashed together.

So sign up for my newsletter to keep up to date with this project as well as lots of other tests I am running this year!

Growbag Collars

There is also a product that exists called a growbag collar. This does a lot of the same things as the plant pot does, but with a nice extra feature.

Less Watering Needed!
Pack of 6 Tomato and Vegetable Growbag Pots
  • Specially designed pot for growing in growbags
  • Set of 6, measuring 26 centimetres across, so three fit neatly on a growbag
  • The inner and outer watering troughs make feeding and watering easy
We earn a commission from any items purchased through this link at no charge to yourself. This helps fund what we do here!
03/01/2024 10:14 pm GMT

The extra feature is the outer ring of these collars works as a water reservoir. It holds water and slowly releases it into the soil. Meaning you need to water even less often.

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  1. Personally I feel there is not enough room for 3 Tom plants in 1 growbag, as for cutting holes, I heat an empty tin can and burn a hole . This hole easily takes a plant in a 3” pot, the lessor hole size prevents water evaporating.
    If you want to split a bag in half as suggested, lay the bag over a broom handle, cut thru the plastic and about half way thru the compost( as it gets compacted). Lift the broom stick and the contents should divide nicely.

  2. There is another way! I knew tomatoes like to spread their roots deep for several reasons so I turned the deep full grow bag on it’s side, squished it a little to stop it from falling over and I will be able to get three tomato plants in with lovely deep roots.

  3. Yes got plenty pots lying around so might as well use them. I tend overspill the water in grow bags.

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