Butternut or White Walnut (Juglans cinerea)
Is a species of walnut native to the eastern United States and southeast Canada.They are very much frost hardy down to zone 3 .
It is a deciduous tree growing to 20 m tall, and 40–80 cm trunk diameter, with light grey bark.
Butternut flowers from April to June, depending upon location. The species is monoecious. Male flowers are slender catkins that develop from auxiliary buds and female flowers are short terminal spikes home on current year's shoots. Flowers of both sexes do not usually mature simultaneously on any individual tree, so 2 or more are required for good pollination.