The Common walnut is believed to be native to the south-east of Europe to the south-west of China. The reason there is no precise native origin is due to the many years of cultivation. The Romans introduced the Common walnut to the UK during their occupancy. It is now widely planted and has naturalised across pockets of the UK. The hoarding nature of the Grey squirrel is thought to have been a major cause of the natural spread of the Common walnut. It is also often found in parks, green spaces and large private gardens.
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Videos
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Photos
It is a deciduous tree and capable of growing to heights of up to 35m. The growth habit is a single stem / trunk and typically upright with a short trunk and broad crown. It is shade intolrerant and requires full sun to thrive. A allelopathic compound called juglone is found in most parts of the tree - particularly the roots. This can stop or slow down the groth of other plants nearby - making it a sort of defence mechanisim so that the nearby ground is more available for sapling Common walnuts. Horses that eat walnut leaves may develop a condition called laminitis (hoof ailment).
ENTIRE TREE
BARK & TRUNK
The bark is smooth and olive-brown on younger trees and silvery-grey with fissures on older trees. The base of the trunk on older trees tends to look a bit stripey - a bit like Snake bark maple.
CANOPY
CROWN
The leaves are pinnate and can have anything from 5–9 paired oval leaflets and one 'terminal' leaflet at the end. They are alternately arranged and are 25–40 cm in length typically. The largest leaflets are the three at the apex and the the basal pair of leaflets are much smaller, this can really help with identification when the tree is in leaf. The leaves are shed from October to November and are a dull yellow colour often accompanied with several black spots. Due to the large size of the leaves the amount of leaf litter is very high.
BRANCHES & TWIGS
LEAVES
Much like the Black walnut the twigs are very chunky and the leaf scars are very distinct being a horseshoe shape. The buds are covered in small sikly greyish hairs and are fuzzy to the touch. The terminal buds are larger than the lateral buds.
FLOWERS
FRUIT
The flowering time for Common walnut is May to June but due to climate change they may flower in April. It is monoecious in nature meaning each tree has both male and female flowers growing on the same tree but different parts. The male flowers (catkins) are very showy and easy to spot whereas the female flowers are quite hidden. The male flowers are green catkins which start off quite rigid and as they begin to release pollen become more relaxed and droop.  They are soon shed by the tree and the ground is covered in thousands of male flowers. After successful pollination by the wind the female flowers will develop into round fruit the size of golf balls.
BUDS
GROUND LITTER
The fruit is shed by the tree in October time and can very quickly cover the ground. Grey squirrels will happily chew through the solid shell to get to the nut inside. The fruit often grows in pairs but can sometimes be in groups of three. Between November and April the tree is fairly dormant and there are very few visible changes to be seen. The most interesting time to study the tree is when both the male and female flowers are present which is usually a good 3 weeks or so around May time.
OTHER USEFUL DATA
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Zelimir Borzan, University of Zagreb, Bugwood.org
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The Biodiversity Heritage Library
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The Biodiversity Heritage Library
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Photographied by Krzysztof Golik, Public domain, via Wikimedia Commons
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Franz Eugen Köhler, Köhler's Medizinal-Pflanzen, Public domain, via Wikimedia Commons
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Amédée Masclef, Public domain, via Wikimedia Commons
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H.M. Dixon, Public domain, via Wikimedia Commons
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Will's cigarettes tree card - credit to cigcardpix via Flickr
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Will's cigarettes tree card - credit to cigcardpix via Flickr
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Lambert & Butler's cigarettes tree card - credit to cigcardpix via Flickr
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Gallaher's cigarettes tree card - credit to cigcardpix via Flickr
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Typhoo tea (scanned from personal collection)
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Rington's tea (scanned from personal collection)
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Carbon performance certificate by Treeconomics for Barcham Pro Tree
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Carbon capture data by Treeconomics for Barcham Pro Trees
OTHER USEFUL RESOURCES
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www.barcham.co.uk
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www.tree-guide.com
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www.chewvalleytrees.co.uk
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www.treesandshrubsonline.org
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https://powo.science.kew.org
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www.woodlandtrust.org.uk
QUICK FACTS
  • ​The Common walnut is believed to be native to the south-east of Europe to the south-west of China.
  • The reason there is no precise native origin is due to the many years of cultivation.
  • The Romans introduced the Common walnut to the UK during their occupancy.
  • It is now widely planted and has naturalised across pockets of the UK.
  • The hoarding nature of the Grey squirrel is thought to have been a major cause of the natural spread of the Common walnut.
  • It is often found in parks, green spaces and large private gardens..
  • It is a deciduous tree and capable of growing to heights of up to 35m.
  • The growth habit is a single stem / trunk and typically upright with a short trunk and broad crown.
  • It is shade intolrerant and requires full sun to thrive.
  • A allelopathic compound called juglone is found in most parts of the tree - particularly the roots.
  • Juglone can stop or slow down the groth of other plants nearby - making it a sort of defence mechanisim.
  • Horses that eat walnut leaves may develop a condition called laminitis (hoof ailment).
  • ​The bark is smooth and olive-brown on younger trees and silvery-grey with fissures on older trees.
  • The base of the trunk on older trees tends to look a bit stripey - a bit like Snake bark maple.
  • The leaves are pinnate and can have anything from 5–9 paired oval leaflets and one 'terminal' leaflet at the end.
  • They are alternately arranged and are 25–40 cm in length typically.
  • The largest leaflets are the three at the apex and the the basal pair of leaflets are much smaller.
  • The leaves are shed from October to November and are a dull yellow colour often accompanied with several black spots.
  • Due to the large size of the leaves the amount of leaf litter is very high.
  • Much like the Black walnut the twigs are very chunky and the leaf scars are very distinct being a horseshoe shape.
  • The buds are covered in small sikly greyish hairs and are fuzzy to the touch.
  • The terminal buds are larger than the lateral buds.
  • The flowering time for Common walnut is May to June but due to climate change they may flower in April.
  • It is monoecious in nature meaning each tree has both male and female flowers growing on the same tree but different parts.
  • The male flowers (catkins) are very showy and easy to spot whereas the female flowers are quite hidden.
  • After successful pollination by the wind the female flowers will develop into round fruit the size of golf balls.
  • The crushed leaves that smell like polish.
  • The botanical name of the English walnut, Juglans regia, means the 'royal nut of Jupiter'.
  • The preferred soil type is sandy - loamy to loamy.
  • The preferred PH is slightly acidic to alkaline.
  •  It can withstand very low temperatures.
  • It is often planted at terraces because it is reputed that it deters mosquitoes.
  • Walnut Frost Crack, Walnut Gallmite and Walnut Leaf Spot are common problems for walnut trees.
  • The leaves are the foodplant for caterpillars of a number of micro moths.
  • The nuts are eaten by mammals, including mice and squirrels.
  • The leaves are used in the treatment of conditions, including swelling of the skin, acne, ulcers, diarrhoea and excess sweating.
  • The leaf is also used in tanning agents and hair dyes.
  • The nuts are reported to help reduce cholesterol, while the shell is used in the treatment of blood poisoning.
  • In 2019 the world production of shelled walnuts was 4.5 million tonnes - over 50% of this was China.
  • The three top countries for walnut production are China, America and Iran.
  • The wood is used for high-end flooring, guitars, furniture, veneers, knobs and handles as well as gunstocks.
  • The lifespan of a Common walnut tree is typically 200 years.
  • The oldest walnut tree on record is located in Spain and is about 530 years old.
  • Other names are Persian walnut, English walnut, Carpathian walnut and Madeira walnut.
PLEASE LEAF ME ANY FEEDBACK / COMMENTS
If there is anything out of place or wrong please contact me. Equally if there is anything you wish to add please let me know. The more information we have about Common walnut the better. Many thanks!