Another Potato question

[cityandthemountains]

I have my potatoes in, early, mid, and mains. Planted them in a good one foot trench and raked up the soil over the top leaving mounded rows.

The foliage started coming up a couple of weeks ago and they are now quite tall. I've heard on 'the grapevine', not this one, that once the foliage appears you should rake up the mud to cover them again. I did this to a few rows last night, but I'm not sure it's the right thing, it seemed a bit rough.

Could anyone clear up the basics of how the spuds are formed. Do they form from the roots downwards or do they follow the foliage upwards?

Any help appreciated.

[Flummery]

Definitely earth them up. It does seem mean, when they've struggled up to the light, to cover them up again, but you will get more roots like this and the tubers form on the ends of these, so the more you get, the higher the yeild. It also protects them while there is still a possibility of frost.

[cityandthemountains]

So would I just dump soil on top of the foliage to cover them completely? I don't have a lot of loose earth near them so I would have to shovel some on?

Do they not need the energy from the foliage to produce the potatoes?

Thanks for the help!

[Kristen]

Make a ridge, with the peak along the row where the spuds are growing, and the "valley" between each row.

Spuds form on "roots" growing off the stem, so earthing up means that the stem can product the "side roots" that will create the Spuds.

Also, spuds must not see daylight, otherwise they go green (green spuds are poisonous), so earthing up stops spuds forming near the surface and thus going green

Earthing up also keeps the frost off them (frost will kill the any tops that are showing)

Yes, they need leaves & daylight to make energy, but they have a huge power-house from the original seed potato, so the easily overcome having their leaves covered up.

My personal view is to let them grow a bit, and then earth them up, so that they replenish some energy before being covered up. I earth-up when frost is forecast, as I think that when they are in the light they grow quite compact, but when they are underground they race up to the surface, so my reckoning is that by only earthing up when frost is forecast I have more chance of them not being too tall to be able to earth up.

But the subject has been debated to death over the years, and there is clearly no "right" method, and none of the earthing-up methods has been found to be detrimental - including earthing up fully when you plant them, so that the spud has to force its way through all that soil to get to day light.

You may want to also cover them with grass clipping [don't use any clipping if the lawn has had Weed and Feed on it] (or straw) once they are fully earthed up. Some spuds wills till form close to the surface and thus go green, and a covering of grass clippings will prevent that. It needs to be quite deep though, its got to last 6 weeks, or more, from last-earth-up to until harvest, and the grass clipping will compact down a lot in that time interval