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What To Do With Used Grow Bags?

If your growing season is drawing to a close and you have some old used up grow bags then you may be wondering what you can do with them. Read on for my top tips and advice on how to recycle used grow bags.

What to do with used grow bags
What to do with used grow bags

Why You Shouldn’t Reuse Grow Bags

There are two main reasons for only using grow bags for a single season.

  1. All of the nutrients will have been used up, making for poor growing conditions.
  2. Growing the same crops in the same spot two years in a row increases the chances of fungus and diseases building in the soil.

No Nutrients

Grow bags don’t have a massive volume of soil in them, so the nutrients are used up quickly, usually after a single season they will be pretty depleted.

You then couple that with the fact that most plants grown in grow bags, cucumbers, tomatoes, peppers etc are heavy feeders and you just speed up the depletion of nutrients in the soil.

Grow bags also usually come with fertiliser already in to help speed up the growth and promote heavier crops of your favourite fruit and veg. This works really well but again means you use up more nutrients because of the sheer size of the plants that end up in there.

Fungus and Disease Build Up

Specific fungi and diseases can start to crop up in the soil when it is repeatedly used for the same crop. This is one of the main reasons that good crop rotation is so important.

This can affect some plants more than others but it is still important to regularly chance what crop grows in what soil.

Because of this, I wouldn’t recommend using a grow bag again, especially for the same plant or family of plants.

So, What To Do With Used Grow Bags?

If you cant use them to grow in again what can you do with your old grow bags? Well, I might sound a bit contradictory here but one thing you can do is grow in them again…

Grow winter salads

You can get another crop out of your grow bags in the greenhouse before following through with one of the other steps below.

Winter salads like lettuce don’t need much nutrition to grow well and will also grow better in the greenhouse.

You can usually get away with growing them in spent grow bags to add some extra value to the cost of buying a bag. Sometimes it may be necessary to add a little extra fertiliser to the grow bags before you plant your salad crops.

You can use organic fertilisers like chicken manure or nettle teas to just reinvigorate the soil a little bit. You will also need to give the grow bag some TLC with a hand fork to loosen the soil up a little bit.

You will probably find that the compost has become a tangled mass of roots which need breaking and removing before anything else can grow in there.

Throw them on the compost heap

The easiest option and the one I tend to take at the end of the growing season is to simply empty the contents of my grow bags onto my compost heap.

This way they will help bulk out the compost heap and the soil will be renewed with nutrients and ready to be used again in a year or two.

Use as a mulch

You can use the old compost as a mulch around plants in your allotment or garden. This will help to keep moisture in the soil in dry conditions and can also work as a weed suppressant.

Use as a soil improver

If you have really sandy dry soil or claggy wet clay soil then using the compost from an old grow bag as a soil improver is a great idea.

Just add the compost to the soil and mix it in to improve the soil.

With dry sandy soils, the compost will help to retain moisture and in clay soils that hold too much water it will help to improve drainage, so you really can’t go wrong here.

Seed Compost

You could also use the spent compost as seed compost. This is because seed composts usually have poor soil by design.

Starting your seeds off in amazing compost is a bad idea as this can actually promote overgrowth and lead to weak, leggy seedlings.

Just make sure that if you do this you pot the seedlings on when they start to develop otherwise you can stunt their growth due to the lack of nutrients in the soil.

You will also want to make sure you remove as many roots as possible from the grow bag compost, otherwise your little seedlings might struggle to fight their way through the roots to the surface.

Use the bags as a weed liner

So you have some options for the compost from a grow bag. But what about the plastic liner, after all, we all know that the plastic isn’t going anywhere anytime soon so is there any use for it in the garden.

As it turns out, there is. the thick black plastic that makes up a grow bag actually makes for a really good weed suppressing fabric.

Use it as a liner under paths to stop weeds from coming up. You can cover it with bark or gravel and it will save you from having to buy a weed liner. Even better is you are using up some old plastic rather than buying even more.

You can also use it as a liner on the inside of raised beds or behind sleeper walls to help prolong their life span. They do this by helping to keep some of the moisture from a raised bed away from the wood making it last longer.

Use the bag as a soil warmer

Because of the fact that the inside of these grow bags tends to be black plastic you can actually use them as a soil warmer in early spring. If you place the bags black side up on the surface of your soil and hold them in place with some bricks then they will both keep weeds away and help to warm the soil.

This will allow you to then get started with some earlier sowings as the soil temperature can be substantially raised from what it would normally be, and the soil should also be relatively weed free, for now at least.