Earthing-up means that more of the stem of the plant is underground, which normally leads to the production of more roots and therefore more tubers.
This year I am again growing my potatoes in a mixture heavy with composted stable manure, because that's what I used last year and it produced a good crop of very clean potatoes.
I was away from home from Sunday afternoon until Wednesday evening. When I got home I was amazed to see how much the potatoes had grown in the three days I had been away. This is the same pot as the one in my first photo.
They need earthing-up again already!
My other First Early potato variety is "Winston", and the plants seem to be growing much slower than "Annabelle", which is probably a good thing because it means they won't all mature at the same time.
"Winston"
Meanwhile, Second Earlies "Charlotte", in their smart new tubs, are not far behind.
"Charlotte"