Seed potato the size of a hen's egg may be planted whole. Larger potatoes should be cut. Use a clean, sharp knife each piece should have 2 strong eyes and plenty of flesh around those eyes. The plant will utilize this stored food during the first 2 or 3 weeks of growth. The more eyes then the greater your yield.
You may be plant immediately after cutting if you have good control of soil moisture (not too wet for a long period of time) or you may dry the pieces in a cool and dark location.
There are many rules of thumb about planting time. The tradition of planting on Good Friday did not originate in the northern regions. That is a little early. Some will plant when the dandelions are in bloom and others wait 2 weeks before average last frost. If you plant by soil temperature then 50 F is the ideal temperature for potatoes to go into the ground. The month of May is fine. Just make sure that you provide three months of growing time.
Planting: Dig a shallow trench, 8 to 12 inches is good. Plant your seed potatoes about 12 inches apart. Cover
with 4 inches of soil. Reserve the remainder of soil for later ‘hilling’.
On average, in approximately two weeks, green leaves will emerge. When the plants have grown to about 8 inches, gently hill with soil, leaving 4 inches of the plant exposed. Hilling both cools the soil and creates space for tuber development. Formation of potato tubers will be at the same depth of the seed piece and higher. Another hilling is beneficial once the plants have grown to 8 inches. If you see potatoes poking out of the hills, add more soil to cover them. Hilling is crucial to establishing your crop. You are building the site for your potatoes to develop as you hill the soil.
A final mulch of shredded leaves will help maintain soil temperature, moisture and will protect the potatoes from the greening affect of sunlight.