I always use grow bags for my greenhouse cucumbers. In particular, I like to use the Tomatorite giant deep fill bags. You can find them on Amazon here, although I will say you will find them much cheaper in a garden centre or, like me, Homebase.
So why would you use a grow bag for cucumbers, well they are perfect if you have a hard floor greenhouse, like me, where there is no soil. They also provide all the nutrients that your cucumbers could ever need in one growing season.
How many cucumbers per grow bag
This may be controversial with some growers as most suggest two plants per bag but I have always grown three plants per bag. This way you are maximising your yield per bag and therefore getting more cucumbers for the same price. I can’t say I have ever had any problems with growing three plants per bag and I have no plans to change!
Now if you are growing cucumbers in bags then they will obviously need some sort of support structure. I go into more detail on this in my how to train cucumbers article but the premise is simple. One can for each plant to grow up with a support bar running along the top to tie it all together.
I will then also tie this into the roof structure to add even more support. You can see this in the photo below.
Well with a grow bag you get a compost full of nutrients that your cucumbers need to grow. These bags are designed for growing tomatoes and indeed I do have some at the other side of my greenhouse doing just that but they work just as well for cucumbers.
I find with just these grow bags I don’t need to add any extra fertiliser. I already end up with gluts of cucumbers where I end up giving them away to anyone and everyone so why would I need more?
Grow bags are also really useful for water retention in the greenhouse. Because the water has nowhere to drain it stays in the bottom of the bag. While this may sound like a problem at first it is actually ideal for thirsty plants like cucumbers.
In a hot greenhouse the soil can dry out really fast, so this extra water retention just gives you a little more leeway between watering. Just made sure you don’t drown the plants in standing water and you will be just fine.
Always go for a deep fill bag where available. The deep fill adds extra room for root growth and also water. So your cucumbers will grow bigger and you won’t have to water them as often, a definite win-win.