Walnut (Black)

The Black walnut tree is native to North Amercia and was introduced into the UK before 1656. In the UK it is typically planted in parks and green spaces as an ornamental tree. In America it is widely planted and used for timber as well as food (edible nuts).

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It is a deciduous tree and capable of growing to heights of up to 40m. The growth habit is a single stem / trunk and typically upright with fewer lower branches. In it's native range it is classed a pioneer species so can spread and colonise open land fairly quickly. It is shade intolrerant and requires full sun. 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 availavble for sapling Black walnut trees.

ENTIRE TREE

BARK & TRUNK

The bark is grey-black and has many deep ridges which often cross cross. On mature trees the bark can resemble diamond shapes. The Sunburst lichen seems to be the most common lichen on the bark. In an open area the trunk is quite short and the crown is fairly broad.

CANOPY

CROWN

During the summer when the tree is in full leaf the canopy is very stunning and allows a fair amount of sunlight onto the ground. In parks and green spaces it is often used as a shade tree. The leaves are pinnate and can have anything from 10 to 23 leaflets. Typically there are 15 leaflets on each stem and they are alternately arranged. Each leaflet is irregularly toothed and around 7 - 10cm long.

BRANCHES & TWIGS

LEAVES

The twigs are quite chunky and the leaf scars are very distinct being a horseshoe shape. The buds are covered in small sikly white hairs and are fuzzy to the tough. The terminal buds are larger than the lateral buds.

FLOWERS

FRUIT

The flowering time for Black walnut is May to June. 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 which look a bit like green ping pong 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. During the Autumn time the leaf colour will change to a warm yellow and against the dark bark it really stands out. Between November and April the tree is fairly dormant and there are very few visible changes to be seen.

OTHER USEFUL DATA

The Biodiversity Heritage Library

François André Michaux (book author), Augustus Lucas Hillhouse (translator), Pierre-Joseph Redouté (illustrator), Bessin (engraver), Public domain, via Wikimedia Commons

Brooke Bond tea (scanned from personal collection)

Carbon performance certificate by Treeconomics for Barcham Pro Trees

Carbon capture data by Treeconomics for Barcham Pro Trees

OTHER USEFUL RESOURCES

www.barcham.co.uk

www.tree-guide.com

www.chewvalleytrees.co.uk

www.treesandshrubsonline.org

https://powo.science.kew.org

www.vdberk.co.uk/trees

QUICK FACTS

The Black walnut tree is native to North Amercia and was introduced into the UK before 1656
In America it is widely planted and used for timber as well as food (edible nuts)
In the UK it is typically planted as a park tree
It is a deciduous tree and capable of growing to heights of up to 40m
The growth habit is a single stem / trunk and typically upright with fewer lower branches
In it's native range it is classed a pioneer species so can spread and colonise open land fairly quickly
It is shade intolrerant and requires full sun.
A allelopathic compound called juglone is found in most parts of the tree - particularly the roots
The bark is grey-black and has many deep ridges which often cross cross
On mature trees the bark can resemble diamond shapes
The Sunburst lichen seems to be the most common lichen on the bark
In an open area the trunk is quite short and the crown is fairly broad
During the summer when the tree is in full leaf the canopy is very stunning and allows a fair amount of sunlight onto the ground
In parks and green spaces it is often used as a shade tree
The twigs are quite chunky and the leaf scars are very distinct being a horseshoe shape
The buds are covered in small sikly white hairs and are fuzzy to the tough
The terminal buds are larger than the lateral buds
The leaves are pinnate and can have anything from 10 to 23 leaflets
Typically there are 15 leaflets on each stem and they are alternately arranged
Each leaflet is irregularly toothed and around 7 - 10cm long
The flowering time for Black walnut is May to June
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
After successful pollination by the wind the female flowers will develop into round fruit which look a bit like green ping pong balls
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
During the Autumn time the leaf colour will change to a warm yellow and against the dark bark it really stands out
Between November and April the tree is fairly dormant and there are very few visible changes to be seen
The seeds have been used in crafts as they produce a dark-coloured dye
The timer is valuable as well as attractive and it is also very durable
The heartwood has a mottled effect
The taproots of Black walnut in saplings are strong and fast growing making transplanting more difficult
Black walnut is more resistant to frost than the Common walnut
About 65% of the annual wild harvest comes from the U.S. state of Missouri
The tree can be tapped to make drinkable sap - just like in Sugar maples
Black walnut has been used for many medicinal purposes including mosquito repellent and a dermatological aid

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 Black walnut the better. Many thanks!

BLACK WALNUT

JUGLANS NIGRA