It does sound a bit early. Are they protected, i.e. under cover, because that would bring them on quicker. You may end up with some surprise 'earlies'!

thank you worthy1, i do not have them under cover, but found a mushy stem on one of the plants two days ago. investigating further i found 3 out of 24 with mushy stems on the all blues, i also have kennobec's. i have to destroy all 32 plants, but of course i checked to see what was underneath. each all blue had ten or more well formed potatoes... so they were early for whatever reason. most of the kennobec had 30 to 35 potatoes each. i don't know if the stem problem brought on early production, but i doubt it. we had a lot of rain and the mulch around the potato stem may have been a contributing factor for bacteria. lesson learned, hard one though.