"Earthing-up". Is it worth doing?

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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?

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