Friday, 22 April 2016

"Earthing-up". Is it worth doing?

For many years now I have grown potatoes in containers. I have described in an earlier post the method I use, so I'm not planning to reiterate that. What I want to discuss today is the idea that the "earthing-up" procedure (aka "hilling") that I and most other gardeners have been using all these years is unnecessary. Let's see what you think...


Traditionally, one puts the seed tubers into a pot which has only a shallow layer of compost in it.




Then as the potato plants grow, you add more compost - probably on at least two occasions - gradually burying the shoots, until the top of the pot is reached.




Allegedly, earthing-up potatoes will increase the length of the underground stems that will bear the new tubers. Researching this, I found the following statement on a website called Wikihow: "Earthing-up potatoes is an important part of the growing process. It involves drawing mounds of soil up around the plant to prevent new tubers from growing and turning green and poisonous. Also many times more potatoes will form from the buried stems. It also helps to prevent blight infection." I'm not sure I agree with all that!


The Royal Horticultural Society (RHS) says this: "Small crops of potatoes can also be grown in large, deep containers, and this is a good way of getting an early batch of new potatoes. Line the bottom 15cm (6in) of the container with potting compost and plant the seed potato just below this. As the new stems start growing, keep adding compost until the container is full. Earthing-up protects newly emerging foliage from frost damage . It also protects developing new potatoes from light. Light turns tubers green and green potatoes are poisonous."


I have seen a few articles recently suggesting that this procedure is in any case just too laborious to bother with. Apparently "studies show" that yields are just as good if you simply bury the seed tubers to a depth of 5 or 6 inches in a pot that is already full of compost - just like planting a bulb. I accept that this is indeed simpler and therefore easier, but I haven't seen any real evidence about yields. When sowing seeds or planting bulbs we are always told not to plant them too deep, because if a seed / bulb has a long journey to make its way to the surface it may use too much of its stored energy, and thus produce a weaker plant.

I am the ultimate sceptic when it comes to challenging tried-and-tested gardening techniques (I know - you'll be saying "Oh, he's just an old dinosaur, set in his ways..."), and I can't help noticing that this new advice comes mostly from Seed Merchants who have a vested interest in selling more potato tubers. Could it be that they are aiming to de-mystify the whole issue, trying to get new gardeners, often youngsters who are cash-rich but time-poor, to try growing potatoes for themselves? Maybe they are. And maybe they're not. I reckon it's worth carrying out a comparative trial. I can't do it this year, because I have already planted all of my potatoes, but I plan to give it a go next year.




What does anyone else think? Is anyone going to do a comparative trial THIS year?

13 comments:

  1. I've grown spuds in pots using both methods and never found enough of difference between them to say which is 'best' although I know which is the simpler and least work intensive. However, I have found that the length of time between planting and harvesting is by far and away the biggest factor in determining crop size.

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    1. When you grow First Earlies and even Second Earlies, it is not size of yield that is the major factor, it is taste and texture - and getting an early crop! (Well, it is for me, anyway). I think if I had an allotment I would probably grow Maincrops too, and that's where the size of yield would be key.

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    2. Yes, I understand that it's all about taste with 1st and 2nds and as I said, no difference with either the fill or top up methods......

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  2. The only benefit I've found in hilling a ROW of potatoes is that it keeps them from falling over early in the season and creating a jumbled mess. I've had no difference in yield between years when I hilled and years when I let things go.
    Containers, in general have better yield probably because the exposed pots collect more heat than the earth does. When using containers I start half full and add the second half of the soil when the stems reach the rim.

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  3. I haven't planted all my potatoes yet so I could trial this, though I'm of the opinion that if it ain't broke don't fix it. I don't mind earthing up as they grow, there isn't that much work involved but I might just have a go at planting up one container with compost to the top at the beginning just to see what happens.

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    1. Jo, if you do try it, please let us know the results.

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  4. Like you I grow early potatoes for taste and texture, I only use containers now but have grown maincrop as well in the soil. I would always earth up just to stop the tubers from greening. My sister grew some under 6" of soil and a layer of thick black plastic and had a wonderful crop.

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  5. How incredibly timely this post is! I was thinking the exact same thing when I planted my potatoes last weekend. Last year, I placed them deeply in the bed and then hilled the soil around the plants as they grew. What I noticed when I dug up the potatoes was that there were no tubers in the top portion of the bed that had been hilled...they were all at the bottom of the bed. I was just about to do the same thing this year, but thought better of it after I remembered that. The day after I planted the potatoes, I filled them in. This would be a fascinating experiment - I for one would much rather plonk the potatoes in and not worry about hilling up the soil - a bit of a difficult task when you are dealing with a raised bed. Perhaps I'll give this experiment a try next year as well using containers.

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  6. Mark I only grow potatoes in tubs & have tried both methods. To my mind neither method gives a better harvest than the other. This year mine have & are being plonked in & filled with compost from the outset. As long as they receive sufficient watering & a bit of feeding later on I get a good harvest. In reply to your bean pole post - they were marketed in the same way. We went for the 8ft canes for beans & the 6ft one for tomato support possibly. We might be returning to the shop tomorrow so will have a look to see if they have any in stock. I shall take a photo of the label for you. We've had ours for 2-3 years now.

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    1. Thanks Jo. I've contacted Gardman, who tell me that their Willow is imported from China! (Groan...)

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  7. How fascinating Mark. As a none digger I have not earthed up my early potatoes but always thought several green potatoes has been the penalty for the omission. I wonder if deep planting really avoids poisonous green potatoes. ( in the past I have just shoved the green ones back in for next year!)
    I also googled do farmers earth up? I did not find a conclusive answer!.i don't mean cover up high when they plant, this is little different from deep planting. How could I live so long and not know the answer?

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  8. I've used both methods and have never noticed a difference with the crop. Earthing up is a nice ritual and feels like you're actively helping the spuds along, but non-earthing methods save a lot of time!

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