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ORIGIN: Selected from a cross between Richter Jubel x USDA S44537. Released in 1946 by USDA and Cornell.

CHARACTERISTICS: 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. Nodes are slightly swollen and green; internodes slightly pigmented and wings are straight and green. 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.

Tubers are oblong with a creamy buff smooth skin. Eyes are shallow except at apical end which is sometimes sunken. Flesh color is white.

STRENGTHS & WEAKNESSES: Ontario is highly scab resistant and has some resistance to late blight and Fusarium wilt. It has some tolerance to harvest bruising.

It sets and sizes tubers late and maturity may be too late for regions with a short growing season. Vines are difficult to top kill. Tubers are susceptible to after-cooking darkening, particularly with late storage. The variety tends to produce tubers in chains when subjected to heat and moisture stress.