I don’t think of looking at the Fingerling potatoes I have in paper bag in pantry until you mention potatoes. I just looked and the growth from the eyes is about 1/8 inch. How much should they be grown out before I plant them? I’m planting the whole potato because they are small - I have 10 of them. Going to plant them in the tallest Mega Garden bag.
Sprouts should be about an inch. If a little more than that, it’s not problem. You can get them to sprout faster if you bring them out into a room with medium light. Keep the temps around 60 to 70 degrees. Regular humidity in Texas this time of the year should be ok in the bathroom or kitchen.
It’ll just take about 1 - 3 weeks, and they should be ready to plant. Remember you want 2 or three sprouted eyes per plant. I am not that familiar with fingerlings, but regular potatoes are cut to about the size of 1/2 a large chicken egg.