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Walnut (Juglans regia) non-native

Explanation of Latin name: The tree produces chemicals called “juglones” that stop other plants from growing underneath them. “Regia” means royal.

Description: deciduous.

  • Shape: is a widely spreading tree with many twisting branches, a big broad trunk and a loose open crown with heavy branches.
  • Leaves: The leaves are made up of small leaflets, similar to ash but without black buds in winter; usually about seven arranged alternately on each side of a slightly yellow stalk. They are not shiny, but have a matt surface and are dark greeny yellow. They are leathery and when crushed smell of shoe polish. They first unfold orange/brown then by mid June they turn green.
  • Flowers: Flowers open just before the leaves. Each tree has male and female flowers.  The male flowers are greeny yellow catkins that are 6 -13 centimetres long and hang from last year’s twigs. The female flowers are 2-5 little clusters of slightly hairy yellow bulbs with red or white styles sticking out from each centre and hang from the current year’s growth.
  • Fruit: The fruit are oval and 4 -5 centimetres across. The outer slightly, soft coat, which is called a husk or shuck, is shiny and green at first.  It changes to dark brown when it is ripe. Inside this is one seed, the walnut, which has a white kernel when it is fresh.
  • Bark: The bark is grey and smooth between wide and deep cracks (similar to ash).
  • Height: 20 to 30 metres tall
  • Spread: Up to 3 metres wide.

Where found: Walnuts are native to south-east Europe, and south-west and central Asia.Walnuts are most commonly grown in the south and  south-west of England. They can grow well in lowlands and mountains but rarely above 800 metres. They grow best in mild climates and prefer deep, well-drained and chalky soil.  They have deep roots and need plenty of water and light. They can easily be damaged by winter and late frosts. Saplings can often be found far from their parent trees as they have grown from nuts that have been carried off and buried by crows and squirrels.

Phenology:

Flowers Leaves Fruit Ripen Fall
May May/June September October October

In May the flowers appear and shortly afterwards the yellow leaves that turn green by mid June. Mid September the nuts can be harvested with their husks still on.  By October the husks fall off and the hard shelled nuts can be gathered.

Uses past & present: Walnuts have a high calorie content, 650 calories per 100 grams, so have been used since Greek times as food. They are also a source of fats, protein, phosphorus and vitamins B and D. They are used now in cakes and pastries, salads, meat, poultry, fish and pasta dishes and as “pickled walnuts” considered a delicacy.  They can be an important part of a vegetarian diet. The oil is delicious on salads and pasta.  A liqueur is made in France from the husks and nut-flavoured wines can be found in several countries.

The leaves and outer green husks are deadly poisons for fish and most animals.

The outer husks have been used to make a dark brown natural dye.

The timber is a fine grained and dark wood that has been used for centuries for making fine furniture and gunstocks. The nuts provide food for many woodland mammals, birds and insects.

Similar species: easily confused with ash.  Leaves and bark may appear similar but the walnut fruits are very different from ash “keys”. The strong, distinctive “shoe polish” smell of the walnut leaf is also a useful distinguishing feature.

Folklore & History of this species: Shelled walnuts look very much like the two halves of a brain.  It is for this reason that the ancient Greeks and Romans believed that walnuts cured headaches.  There was also a Roman belief that sleeping in the shade of a walnut tree caused headaches and uneasiness. This may be because the trees produce chemicals called ‘juglones’ ………..that stop other plants from growing underneath them and some people still believe such lying under such trees makes them feel unwell.

The first walnut trees are believed to have been grown by the shores of the Caspian Sea and north India. The Greeks were the first to value the oil as food. It was the Romans who grew them in many other parts of Europe, from the fourth century in France and England where they died out in the Dark Ages ( AD 410 – 700 ) Then they  were occasionally grown in gardens but  were not seen in the wild again until mid eighteenth century. 

Propagation and growth: Natural distribution by airborne seed. Should not be planted near buildings or drains. Seed quickly loose there vigour but fresh seed germinate quickly. Unlike Black poplar and hybrids not easy to grow from sets.