I don't wash our potatoes until we are preparing them for a meal. I was taught that they store better, lasting longer in storage if you don't wash them. I will brush off excess soil when I dig them....but very carefully because it is easy to damage them. My grandfather stored his freshly-dug potatoes directly on the ground piled in a cool, dark corner of a little lean-to with a dirt floor that he built behind his garage and his potatoes lasted for many months stored that way. I guess I learned not to wash them prior to storage just from watching him.

I think a lot depends on how big a crop is as well as how long someone plans to store them. With a small crop that will be eaten up in just a couple of months, I doubt it hurts too much if you wash them right after picking them.

It is, of course, recommended that potatoes be stored without washing them in order to prolong the amount of time they last in storage. The same is true with onions. I've always cured potatoes (and onions) for a week or two in a dry, shady spot, unwashed, for a couple of weeks before putting them in storage and they last a long time in storage. I tried washing them right after harvest one year to see if it made a discernable difference and found that started sprouting much more quickly when I did that, so I never have done it since then.

I have never washed potatoes of any kind, I often let them lay in the sun for a few hours to let the soil dry and then brush then with a paint brush. I did however wash my ornamental sweet potatoes last year because I had run out of storage room and had to just put them in the bedroom floor. They stored very well and one is already blooming this year. These are not really good potatoes, they are too dry and unsweet

I normally don't wash mine, but the ground was so wet this year when I dug mine that I had mud sticking to them so I did wash off the mud. If you do it too soon, or with too much water pressure, it will take the peel off, so I would rather not wash at all.