Too many.... again
I am turning my greenhouse into a sea of growbags. Having grown too many tomatoes – again – but not having the strength to decide which to get rid of – again - I’m on my 17th growbag so far. I’m not entirely sure I couldn’t squeeze in a few more if I budged things up a bit. It is getting to be an expensive habit, but I’m hooked.
Super-versatile, space-saving, easy to use, growbags are a brilliant invention for gardeners – especially those who have to shoe-horn their veg into small spaces.
However half the battle with them is figuring out which tricks you have to use to get them performing at their best. You see, you can’t just chuck them down on the floor and expect to plant straight into them.
Well – you can: but the problem is that growbags are notoriously stingy, containing just 30-40 litres of compost (half an average bag of multi-purpose) and about two inches thick. Imagine growing a mature beefsteak tomato in a pot 5cm deep. Exactly.
So the first thing to do is to tackle that depth problem.
Fluffing up helps: your growbag has probably spent much of its career to date underneath several hundred other growbags, and that adds up to a lot of weight. This means the compost inside has been systematically flattened and all the air driven out of it – one of the reasons it’s only 5cm thick.
Pick it up like a pillow and plump it up, massaging it back into life and breaking up lumps and hard edges. You’ll find it magically transforms into something less like a paving slab and more like a soft, welcoming bed into which you’d happily put a plant.
That done, it’ll go from 5cm to … ooh…. 8cm or so. This is fine for smaller plants: aubergines, peppers and chillies will be quite happy. But it’s still not big enough for your average eight-foot tomato. To get around this, you can try one of three tricks: all have their advantages and drawbacks, and I’m trying all of them somewhere in the greenhouse. We’ll see which gets the best results later in the season.
| 1. The Double Growbag Method |
 Before...  ...and after |
This is probably the simplest way to sort out the thickness: just stack the growbags on top of each other (two is usually enough).
Advantages: plenty of depth to hold water and roots; you can grow three tomatoes in this reasonably well |
| 2. The Two-Plant Growbag Method |
 Before...  ...and after |
A friend of mine told me about this one: amazingly simple way of getting the most out of a single growbag.
Advantages: more than enough compost in each pocket to sustain even the largest of tomato plants, and you only use one growbag |
| 3. The Sideways Method |
 Before...  ...and after |
For this you’ll need a gadget. I’m trying out the Growbag Frame, made of recycled steel and, as I’ve found, quite sturdy. It’s a little bit fiddly to set up (there’s a lot of inserting and then re-inserting poles to do) but nothing I couldn’t handle; other than that, so far, so promising.
Advantages: uses just one growbag, yet allows room for three plants |
So which is best? Well: I don’t know. Not yet. But I’m expecting good results from all three methods: and they’ve got to be an improvement on the lone-growbag-on-the-floor model. I’ll report back later in the season and let you know how I got on.
Great post…Im interested to see your results. I have one of those grow bag frames too and I am hoping for lots of yummy toms.
What at lot of faffing about! Why not just buy 20 lt (ish) plant pots, and use ordinary multipupose compost in them? Or buy 60 lt bags of multipurpose, pour half into an empty compost sack, and use each of these stood on their ends with the sides folded down (effectively 30 lt grow bags) as a pot?
Thanks MS: so far I’m quite impressed by the growbag frame, mainly because it’s so obviously going to put up with quite a bit of wear and tear. Fingers crossed it lives up to first impressions!
Nick: actually I was going to go on about how you can use ordinary compost sacks as growbags but ran out of space (I may mention it in a later Growbag Chronicle!) You are quite right: you can just buy a sack of compost, make holes in it just like a growbag (or fill half a sack) and grow up to twice as many plants in it. It’s no cheaper, just a little less plastic involved.
Re the plant pots: there I disagree. The plants simply can’t stretch their roots out as well in a pot. I find if plants can spread ‘sideways’, even if there are other plants in the way, they thrive far better.
On the other hand – faffing about just about describes what I was thinking as I fiddled around setting this lot up! Hopefully the end result will be worth it…
Hmmm, roots spreading sideways better than those going round and round in a pot?
Intuitively I’d have thought the volume of compost/water/nutrients would be what matters, and that the route the roots take was pretty marginal…but maybe not!?
That’s an experiment you can set up next year!
How did your trial of the divide and conquer grow bags go? It wasn’t a great year for tomatoes (according to Monty Don) but interesting to know how you got on with the frame as opposed to the other methods. I’ve been using the frame this year and thought it was brilliant especially as you can move it around out of the wind and into the sun. You’re right about it lasting a long time – galvanised steel should outlast me!
Hello Digby, I agree with Monty – not a great year for tomatoes. They suffered in the spring drought then refused to ripen in the gloom. However, catching up fast now and have a greenhouse dripping with so many red tomatoes I’m starting to cook them up to freeze – always a good sign when you can’t eat them fast enough!
I like the frame very much to use – like you say, it’s sturdy and you can move it around. However – I really think a single growbag, even on its edge, is never enough to produce good plants. The only two sets of middling to poor plants I’ve had this year have been the ones grown in single growbags. The ones in double-stacked ones, and particularly the ones planted two to a growbag cut in half, have done fine (still not as good as in the ground, mind you).
So if they find a way of adding a second growbag to that frame I’d recommend it unreservedly!
In conclusion: method 2 (cutting growbags in half and planting two plants to a bag) worked by far the best. Method 1 (double growbags) was reasonably good; the frame was the worst but only because of the single growbag issue. As supports they were excellent