Juglans cinerea - Butternut

Butternut (Juglans cinerea) is a beautiful fruit tree native to North America. It is a cousin of our common walnut. Like the latter, it bears deciduous compound leaves and produces flavourful walnuts. With its broad silhouette and sturdy trunk, it finds its place in large gardens. Appreciated both for its generous shade and its oil-rich nuts, this walnut tree also offers light-coloured wood prized in carpentry. Hardy down to -30 °C, it is an excellent ally for biodiversity, particularly for squirrels and birds.

Butternut (Juglans cinerea), sometimes called white walnut or oilnut, belongs to the Juglandaceae family, like other walnut trees. Native to eastern North America, its range extends from southern Quebec and New Brunswick in Canada to northern Alabama and Arkansas in the United States, including regions such as Minnesota and Missouri. It prefers rich, moist, well-drained soils, often near watercourses. This species is typically found in mixed deciduous forests.

Juglans cinerea is a medium-sized deciduous tree, reaching 12 to 18 m in height, with a trunk diameter of up to 40 to 80 cm. Its bark is light grey, smooth in young specimens, becoming fissured with age. The compound and odd-pinnate leaves measure between 40 and 70 cm in length and consist of 11 to 17 oblong lanceolate leaflets, each measuring 5 to 10 cm in length and 3 to 5 cm in width. The foliage is downy, its yellowish-green hue is brighter than that of many other trees. In autumn, before falling, it turns a decorative golden yellow.

The butternut flowers in spring, usually in May or June. The tree is monoecious, bearing separate male and female flowers on the same individual. The male flowers appear as pendulous, cylindrical, yellowish catkins, between 5 and 10 centimetres in length, while the smaller female flowers appear in small clusters at the tips of the current year's shoots. The fruits are oblong walnuts, measuring 5 to 10 cm in length, encased in a sticky, downy green husk. When ripe, the husk splits to release the walnut, whose thick, grooved shell contains an edible seed with a rich, oily flavour.

Butternut exhibits rather rapid growth, but its lifespan is short, rarely exceeding 80 years. Its habit is spreading, with an open, rounded crown. The branches are sturdy and widely spreading, giving the tree a majestic silhouette. This species is currently threatened by butternut canker, a fungal disease that has decimated many populations within its natural range.

The harvest: the walnuts are typically harvested in mid-September, when the ripe fruits fall naturally to the ground. The trees begin producing walnuts around 20 years of age, reaching peak production between 30 and 60 years. After harvesting, it is best to dry the walnuts with their husks (the outer covering) for about two months, until the husk turns black and can be easily rubbed off. Once the husk is removed, the walnuts can be eaten as they are or used in cooking; they impart a mild, slightly sweet flavour to dishes.

Storage: to preserve the walnuts, store them in an airtight container at a temperature between 0 and 5 °C, with a relative humidity of 80 to 90%. Under these conditions, the walnuts can be stored for at least two years.