Black walnut is a valuable timber tree and a notable neighbour: it releases a chemical that suppresses some other plants.
Identifying walnut
Scientific name: Juglans
How to recognise black walnut
- Alternate, pinnate leaves with 15 to 23 leaflets, often without a leaflet at the tip.
- Round, green husks about the size of a tennis ball, each holding one very hard nut.
- Dark bark in deep diamond-patterned ridges.
- Twigs with chambered pith.
The husk
The green husk of the fruit contains a dye that stains skin and clothes brown. Handle the green husks with gloves. Inside is a hard, ridged nut with a sweet but strongly flavoured kernel.
Juglone
Black walnut produces a chemical called juglone that can stunt or kill some plants growing close by, including tomatoes, apples and many ornamentals. Gardeners avoid planting those species under walnut. Many plants tolerate it, so check a list before choosing.
Butternut and other walnuts
Butternut (Juglans cinerea) has 11 to 17 leaflets, sticky hairy twigs and an oblong nut. It has been devastated by butternut canker, a fungal disease. English (Persian) walnut, the walnut of the shops, has 5 to 9 leaflets and smooth, pale grey bark.
Uses
Black walnut wood is dark and valued for furniture and gunstocks. The nuts are used in baking.