Sow at a depth of approx.
5.85 inches (15.0 cm) and aim for a distance of at least
11.7 inches (30.0 cm) between Potato plants.
By our calculations, you should look at sowing Russett Norkotah about 14 days before your last frost date.
As Russett Norkotah is tender, ensure temperatures are mild enough to plant out - wait until after your last frost date to be on the safe side.