[Broadhaven]

I have earthed up my Lady Cristl potatoes once but have not managed to do it again and the leaf are about 1ft now. Does it matter if I don't earth up again?

[aelf]

If you can't earth up again, I would cover the sides of the rows with mulch (grass clippings, chopped weeds etc) to ensure that any spuds that are swelling near the surface are well covered and don't go green. The mulch also helps to keep moisture in the soil.

[Stevens706]

Keep a lookout for the developing potatoes poking out the soil and cover them up with soil or as aelf suggests

[Spana]

Last year I tried earthing up with grass clippings as suggested above on a short row of first earlies, Premiere.
I left the soil flat after planting and didn't pull any soil  around them at all.  The grass clippings were put on in layers as they grew. 
It worked so well  that i've done the whole lot this way this year. 

So if you have mowings from a lawn use them round your Lady Cristl. It worked better than soil for me :happy: