Walnut (Juglans regia)

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Walnut is a deciduous broadleaf tree native to south-east Europe to south-west China.

Common name: walnut

Scientific name: Juglans regia
Family: Juglandaceae

UK provenance: non-native

Interesting fact: the best wood is at the base of the tree, so walnuts are often dug up for timber, rather than felled.

What does walnut look like? 

Overview: can grow to 35m. They typically have a short trunk and broad crown, though can be narrower if grown in a woodland situation. The bark is smooth and olive-brown when young, developing fissures and fading to silver-grey with age. Twigs are stout, green and curving.

Leaves: shiny and pinnate (feather-like), with 5-9 paired oval leaflets and one 'terminal' leaflet at the end.

Flowers: male flowers are drooping yellow-green catkins 5–10 cm long, and the female flowers appear in clusters of 2-5.

Fruits: pollinated by wind, female flowers develop into a fruit with a green, fleshy husk and a  brown, wrinkled walnut.

Look out for: crushed leaves smell like polish.

Could be confused with: black walnut (Juglans nigra). Common walnut has fewer leaflets than black walnut. Common walnut leaflets are also more oval in shape and have smooth, untoothed edges.

Identified in winter by: the inside pith, or spongy centre, of the twig is not segmented. Buds have horseshoe shaped leaf scars, or marks, left by fallen leaves, at their base.

Where to find walnut

Found throughout the UK, short winters and more sunshine provide the perfect growing and fruiting conditions for walnut. Walnut prefers well-drained, fertile and alkaline loam soils (a soil that is not very clayey or sandy). It is often found in large gardens and parks. 

Value to wildlife

The leaves are the food plant for caterpillars of a number of micro moths, and the nuts are eaten by mammals, including mice and squirrels.

Mythology and symbolism

The walnut's botanical name, Juglans, originates in Roman mythology. According to an ancient myth, Jupiter, who was also known as Jove, lived on walnuts when he lived on earth. Therefore Romans called walnuts Jovis glans, meaning 'the glans of Jupiter.' The botanical name of the English walnut, Juglans regia, means the 'royal nut of Jupiter'.

How we use walnut

Walnut was originally grown for its nuts and was introduced by the Romans for that purpose. Later it was grown for its timber, which is fine with a decorative, wavy grain.

Threats

The English walnut is susceptible to fungal diseases, as well as walnut blight, which causes small black spots on the leaflets and can lead to dieback of new shoots and damaged fruit. Walnut leaf blotch can cause leaves to fall prematurely but doesn't cause lasting damage to the tree.

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