Discover the best growing method for producing high potato yields
Image: Potato ‘Swift’ from Thompson & Morgan
Our very own horticultural expert, Sue Sanderson, recently set up a series of informal potato trials to see which growing method produced the best yield. Using seed potatoes, Sue experimented with different sized tubers, found out what happened when she cut some in half, and compared the modern ‘lasagne method’ with traditional ‘earthing up’. While not conducted under strict scientific conditions, Sue’s trials produced some clear winners. Here’s how our resident expert recommends growing potatoes…
Frequently asked questions about growing potatoes
The ‘Kestrel’ variety is an easy to grow and delicious potato variety
Image: Potato ‘Kestrel’ from Thompson & Morgan/©Alamy Stock Photo
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 by the minute.
In my small town garden I tend to opt for potato growing bags that can be easily moved around. The other advantage is that I can just turn the bags out and harvest the crop without the need for any digging! Over the years I’ve been asked for lots of advice about growing potatoes this way. Here are the most frequently asked questions that I set out to test:
- Do larger tubers produce more potatoes than smaller tubers?
- Will I get more spuds if I plant more or 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 (sprouts) 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 before planting.)
- How does the ‘lasagne’ method compare to the traditional ‘earthing up’ technique?
The potato trial variables
The potato plants in the trial received plenty of water
Image: Peter is Shaw 1991/Shutterstock
By mid April, the trial seed potatoes were chitted and ready to plant. I chose a second early variety, ‘Charlotte’ and on a damp, grey spring morning I planted up the following seven 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
The potato trial results
It’s important to note that this trial happened during a very wet summer, and so isn’t applicable to everyone’s growing conditions. Here are the surprising results:
Large tubers vs. small tubers
Large tuber results
Image: Sue Sanderson
Small tuber results
Image: Sue Sanderson
The size of the initial seed potato doesn’t seem to make any difference at all to the yield. 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 the size of the seed potato doesn’t influence yield.
More tubers vs. less tubers
More tubers results
Image: Sue Sanderson
Less tubers results
Image: Sue Sanderson
One bag was planted up with two seed potatoes while another was planted up with four. There was very little difference in overall yield, however the potatoes from the ‘Less’ bag seemed slightly larger, so maybe it’s better to use fewer seed potatoes and spread them across more bags if you prefer larger potatoes.
Conclusion: Give your seed potatoes more space to get larger potatoes from your bag.
Halved tubers
Halved tuber results
Image: Sue Sanderson
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.
‘Earthed up’ planting vs.‘lasagne’ method
Lasagne method results
Image: Sue Sanderson
I wasn’t expecting this, but the lasagne method was the only bag that outperformed the earthed up control bag quite significantly!
The lasagne method describes planting the seed potatoes in layers in your bag, like a lasagne, with all the compost added in one go. Up until recently, we always recommended that potato bags should be ‘earthed up’. This means filling the bag by a third, placing the seed potatoes on top, and then adding more compost until the bag is two thirds full. Some weeks later, when the foliage appears above the soil, the bags would be topped up with compost to cover the stems and mimic the normal earthing up process used by gardeners outdoors.
Conclusion: In future I will be using the lasagna method. It’s much quicker and easier to plant the bags up, and the yields speak for themselves.
We’d love to know if your trials match Sue’s results. Please share your potato growing stories over on our social channels. For more information and advice about growing your own spuds, visit our hub page.
Plants and gardens have always been a big part of my life. I can remember helping my Dad to prick out seedlings, even before I could see over the top of the potting bench. As an adult, I trained at Writtle College where I received my degree, BSc. (Hons) Horticulture. After working in a specialist plantsman’s nursery, and later, as a consulting arboriculturalist, I joined Thompson & Morgan in 2008. Initially looking after the grounds and coordinating the plant trials, I now support the web team offering horticultural advice online. I have a keen interest in drought resistant plants and a passion for perennials, particularly hardy Geraniums. I previously stood as regional secretary for the International Plant Propagation Society which gave me lots of opportunities to see what other horticulturalists were up to in their nurseries and gardens.
Henry the Poacher, 28th March 2016
When I was at school during the 1950s my Dad always cut the larger tubers in half with chits on both ends. This was to make them go further (we were a low income family). Instead of drying the cut surfaces, as you have suggested, he just used to dip the cut face in soot or wood ash “to keep the slugs away”. I don’t think it often failed. I’ve been growing my own veg for most of the past 40 years, and have used this method where required. I simply keep the largest tubers with lots of chits to the end of the last row, in case I’ve miscalculated and don’t have enough, then cut the final two or three to make up enough to complete the row if required. I’ve found it usually works OK, and there is no difference in the yield, each half producing the same number of spuds as if it were a whole tuber.
I haven’t tried the lasagne method in a bag or tub, but I would definitely say that you will NOT get a higher yield per tuber by packing more into a given space, as each tuber needs a specific volume of soil to produce its best. If they have to fight for space, the overall production will suffer. I have found this to be the case when I have grown early earlies in plastic tubs to avoid frosts.
I hope this may help.
Henry
Thank you for all these interesting facts about potatoe growing. I would like to try the lasagne method in open ground, and wonder if this could be successful ? I welcome your thoughts !
With best wishes,
Helen.
That’s an interesting idea for a small vegetable plot. I’ve never even thought about growing them in this way in open ground. It would certainly be interesting to try.Perhaps you could do your own potato trial with one row of lasagne method and one row of single tubers. I’d be fascinated to hear how you get on.
Thanks for a really informative blog. I am going to have a go this year with the lasagne method, but I’m going to use all 5 tubers. I will let you all know the result
Give my love to Annie!
Good luck Yvonne, let us know how you get on!
Interesting thank you Sue. I have used the lasagne method for several years and always been pleased with the results.
Yes Steve, it certainly seems to be more successful than the traditional method… and a lot simpler too!
Thanks for all this very straightforward advice, I think I am going to try growing some this year, and have ordered Charlotte potatoes, one of my favourite varieties from the greengrocer: I hope the homegrown version will be even better!
A friend has bought himself some seed potatoes too, so I am sending him a copy of your instructions plus a few grow bags. We will have a contest to see whose crops produce the most!
Thanks for a very practical, easy to follow guide.
Sincerely yours, Eunice.
It’s great to hear that you are going to give it a try. Best of luck. Let me know how you get on and which of you wins the potato growing contest!
Thanks to all who have tested and tried different potato growing methods. This 2013 year has been my first to have a go at spuds in a bag. The earth up method was used and won a few lovely tasting potatoes. Next year will be the lasagne method. The reason for this post is to encourage others to have a go. The taste of newly lifted spuds is unbelievable.
Great blog! I see that the advice that T&M are giving is for 5 tubers in a bag, lasagne style (love that term!), so i’d be interested to try that along with your 3 tuber per bag to see if the yield differs. I’d also be interested in how different types of growing matter affect things. I can’t re-use my tomato growing bags, obviously, and it’s not very cost effective to buy in bags of compost each year for the potato planters. I’m also left with an excess of blight-infected Solanum family compost that is more than I need to grow anything else. Finally got hold of an allotment this year so i’ll have more space to grow things and can therefore rotate properly. I’m also hoping to grow the Sarpo collection, if it comes back into stock, and hopefully avoid blight altogether.
Hi Nyck, thanks for your comment. Do let me know how your 5 vs 3 tuber test goes – I’d be very interested to hear how you get on.
Hi Julie. I used two tubers at the bottom and one further up for the lasagne method. I think that giving them a bit more space certainly does seem to help and this seemed to be backed up by the results of the ‘more vs. less’ experiment.
In the Lasagne method, I see that you used three tubers. How did you layer them? Two at the bottom and one further up, or each one on a separate level? Do you think that giving each tuber a bit of extra ‘elbow room” using this method was what increased the yield?