Lots of questions:
First, potatoes are mostly propagated vegetively. (splng) In other words they are cloned. The genetic makeup is all the same. Seed potatoes are certified disease free. Nothing more. Yes, your returns will diminish if you get a disease. If your lot is free from disease and you never put any grocery store potatoes, nor peelings on it, you can most likely propagate your own stock for many years with no problems.
Green potatoes are OK to plant.
How small is too small? I like to cut potatoes with two eyes on a piece. I like the pieces to be about as big as a walnut or a little bigger. So it takes a potato around 2 to 3 inches to do that. The reason I don't like to plant a whole potato is because each eye will send up a vine, there are a dozen or so eyes on a spud, and the vines are then too crowded, so you will get 25 to 50 small potatoes (marble size), where if you plant a set with only two eyes you are likely to get from 4 to six nice tubers.
OK, potato growers secret. As you dig a hole to put your sets, put a tablespoon of ammonium nitrate in the hole with the set.
Potato seed: Yes, you can propagate potatoes from seed. Keep your eyes open for what look like little green tomatoes on the potato vines. This is the fruit. Extract the seed the same as you would tomato seed. Now you will have a genetic variation and you can pick the best tubers to propagate vegetively. You may find some better adapted to your plot.
I have some photos to illustrate what I mean about the marble sized tubers. I will have to find them.
Storage: How deep does the frost go in the ground there? What I do is dig a pit about 18 to 24 inches deep and put the potatoes in there and cover it up. I then put some straw or leaves on top to add some insulation. The potatoes will keep until March just fine.
Last edited by jal_ut
on Fri Sep 23, 2011 4:15 am, edited 1 time in total.
Gardening at 5000 feet elevation, zone 4/5 Northern Utah, Frost free from May 25 to September 8 +/-