The Walnut Family
What are they?
This is a family consisting mostly of medium to large trees with compound leaves, with species found throughout much of the world. The male and female flowers are carried in separate clusters but on the same tree; in the walnuts, the male flowers form catkins while the female flowers are carried in small clusters of typically 1-3. In the wingnuts, both the male and the female flowers form long catkins, those of the female flowers developing into very long, pendulous clusters. This family contains a number of species that have important commercial value for their nuts and wood.
Where are they found?
There are no native members of the walnut family in the UK, but one or two species are occasionally planted as ornamentals in amenity areas, cemeteries or on roadsides.
Identification
The combination of pendulous catkins coupled with compound leaves helps to define members of this family. Within the family, a combination of flower and leaf detail should identify the species, while the presence of fruits can help too.
White Walnut Juglans regia
Introduced from south-east Europe or Central Asia and long in cultivation for its fruits and wood. Most records are of old, mature specimens on former garden sites, hedgerows and large estates, but nuts burried by squirrels often also produce seedlings on roadsides and rough ground. Flowers June. A deciduous tree to over 20m in height. Leaves glossy with 5-9, rounded leaflets. Nuts contained in fleshy green cases that have smooth and shiny surfaces. Bark smooth, often with shallow, vertical lines.
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Black Walnut Juglans nigra
Introduced from North America for its fruits and wood. Uncommon, but planted in a few forestry lots and rarely as an ornamental in cemeteries and amenity areas. Flowers April-May. A deciduous tree to over 30m in height but often much less. Leaves large, with 9-23, long-tapered leaflets, the end leaflet often reduced to little more than a spike-like extension of the mid-vein. Nuts contained in fleshy green cases that have rough surfaces. Bark rough, strongly ridged and fissured. Leaves have a distinctly lemony smell if crushed.
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Caucasian Wingnut Pterocarya fraxinifolia
Introduced from Central Asia as an ornamental and occasionally recorded from amenity areas, cemeteries and similar places. Flowers April to May. A deciduous tree to over 30m in height. Leaves large, with 7-27, leaflets. Winter buds highly distinctive, having the developing young leaflets exposed, covered in brown, scaly down and not protected by bud scales. The long, seed-bearing trusses hanging from the trees in late summer are distinctive and eye-catching.
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