Selected from a cross between Richter Jubel x USDA S44537. Released in 1946 by USDA and Cornell. Ontario is a very late maturing variety with high yields of medium specific gravity tubers. It is grown primarily in Maine, Wisconsin and Michigan.
Plants are medium to large, erect and spreading.
Stems are medium size and slightly angled. Leaves are long and broad, scantly pubescent and have a green midrib. Calyx lobe tips are long, slender and very slightly pigmented. Corolla is small, pale lilac, or pale lobelia violet in center of each petal and white at edges. Anthers are empire yellow with pollen medium to poor.