If you have grown potatoes before you will know the feeling of disappointment when you harvest your potatoes and what you have in front of you is a poor specimen of potato.
Why not switch to planting one tuber per 8 litre potato growing bag, and not only will you be stunned by the yields, you won’t believe how easy it is to achieve them.
The method, hit upon during technical trials at our HQ, opens up potato growing to everyone – even those without a garden. The small but durable bags will sit happily by the front door or on a deep window ledge. More than 80 tubers were harvested from just one of these bags, nearly treble the number harvested from each tuber in the larger sacks. The results came from our new Potato Jazzy – an exclusive new generation first early, bred for maximum yield and flavour.
How to grow potatoes in bags
- Simply fill the sturdy potato bags by one third with good quality multipurpose compost, and place your ‘chitted’ seed potato on top of the compost. Add another layer of compost to fill the rest of the bag.
- Now all you need to do is water it, place the potato bag in a bright, frost free position and wait for it to grow.
- Feed potato plants every other week with potato fertiliser and water the bags when the compost begins to dry out.
How to harvest potatoes
- Harvest times will vary depending on the growing season and the size of tuber you want.
- Start to harvest first earlies as ‘new potatoes’ when the plants begin to flower, approximately 10 weeks from planting. It’s worth having a gentle dig below the surface to check the potato sizes – if they’re too small simply leave them for another week or so, otherwise lift them and enjoy!
- Maincrop varieties are usually left for at least two weeks after the leaves and haulms (stems) have withered, to allow the skins to set. Cut down the stems with secateurs to just above soil level as the leaves wither and yellow, or if they show signs of blight.
- Second cropping tubers are often called Christmas potatoes. These winter potatoes can be harvested as required from November, or left in the soil until Christmas. Cut down the foliage as the leaves wither and yellow, and protect them from frost by covering the potato growing bags with a thick layer of straw or moving them into the shed or greenhouse.
For more information view our full how to grow potatoes guide.
Sue’s (Very Unscientific) Potato Trials
Harvesting potatoes is my second favourite garden task, beaten only by lifting parsnips! You can feel your excitement building as you lift each tuber from the ground, gently rub it clean of soil, and watch your hoard of spuds grow minute by minute. In my small town garden I tend to opt for potato bags that can be easily moved to give them sufficient space – particularly as the top growth starts to get a bit wild. The other advantage is that you can just turn the bags out and harvest your crop without the need for all that digging!
Annie, potato trial supervisor extraordinaire
Once a fortnight I run a horticultural Q&A session on Thompson & Morgan’s Facebook page and every spring I receive a heap of questions about growing potatoes. So this spring I decided to conduct a few experiments – just for my own curiosity really, but I think the results are worth sharing.
Growing potatoes in bags – the traditional method
The trials were pretty simple really; a comparison of yields to answer the following burning questions:
- Do larger tubers produce more potatoes than smaller tubers?
- Will I get more spuds if I plant more/ less tubers in a potato bag?
- Does the old wartime method of cutting tubers in half really work? (The theory is that so long as both halves have decent chits then they should grow as two separate plants, thereby making your seed potatoes go a bit further. Once cut, they need to be left so that the cut surfaces can dry out a bit before planting.)
- How does the ‘Lasagne’ method compare to the traditional ‘earthing up’ technique?
Growing potatoes in bags – the lasagne method
Now, I realise that this requires some explaining. Up until last year we always recommended that potato bags should be filled by one third, a layer of potatoes placed on top, and then more compost added so that the bag is two thirds full. Some weeks later, when the foliage has appeared above the soil, the bags would be topped up to cover the stems and mimic the normal earthing up process used by gardeners for many years. However one of our directors had tried a different technique; the ‘lasagne’ method! Basically the tubers are planted in layers and the bags filled up all in one go, with no earthing up to be done later.
More vs less tubers
By mid April the seed potatoes were chitted and ready to plant. I chose a second early variety, ‘Charlotte’, just because they were on a special offer – I love a bargain! On a damp, grey spring morning I planted up the following bags:
Control/ Earthed up: 3 medium sized seed potatoes, earthing up method (no experiment is complete without a ‘control’ test to compare the others tests to)
Lasagne Method: 3 medium sized seed potatoes, ‘lasagne’ method
Large tubers: 3 large seed potatoes, earthing up method
Small tubers: 3 small seed potatoes, earthing up method
Less tubers: 2 seed potatoes, earthing up method
More tubers: 4 seed potatoes, earthing up method
Halved tubers: 1 seed potato cut into 2 halves, earthing up method
Large vs small tubers
The results are in!!
Now I must admit that this year I didn’t have the time or energy to give my garden the attention it deserves, so the trials received a splash of water now and again when I remembered. Not that they went short of water – this summer was one of the wettest I can remember. In fact, I was fully expecting blight to ruin the crop, but by some miracle they were spared. Nonetheless, from chatting with other gardeners it seems that this year was not the year of the spud! In fact, this year yields were shockingly poor, although what I harvest have was of very good quality.
So… excuses made, here are the results:
Large tuber results
Small tuber results
Large tubers vs. Small tubers: It didn’t seem to make any difference at all. In fact, the smaller seed potatoes produced one or two more tubers than the larger ones!
Conclusion: Who said ‘Size matters’? The results show that it doesn’t
More tubers results
Less tubers results
More tubers vs. Less tubers: Once again, there was very little difference. Actually, the potatoes from the ‘Less’ bag seemed slightly larger so maybe it’s better to use fewer seed potatoes per bag and spread them across more bags for maximum yields.
Conclusion: Give your seed potatoes some space. Sometimes less is more!
Halved tuber results
Halved tubers: Now this bag was a surprise. Call me a sceptic but I really didn’t hold out great hopes as it only contained one seed potato (2 halves) in total. Whilst the potatoes harvested were not the biggest, the yield was still comparable to that harvested from the other bags.
Conclusion: Larger seed potatoes can be cut in half to maximise yields, so long as both halves have eyes.
Control/Earthed up results
Lasagne method results
Control/Earthed up vs. ‘Lasagne’ method: The big success story of my trials. I wasn’t expecting this, but the lasagne method was the only bag that outperformed the control bag quite significantly!
Conclusion: In future I will be using this method. It’s much quicker and easier to plant the bags up, and the yields speak for themselves.