Black locust trees are a native species of America and in the past it was heavily used for construction as the timber is very strong. It is now widely planted around the world both as an utilitarian and ornamental tree. It was introduced into the UK in 1636. In Exeter they are only planted as a ornamental tree and are found in many parks and green spaces. They are a fast growing species of tree and usually live between 60 - 100 years in planted areas. In their natural habitat they can happily live for up to 300 years. In some areas it is also know as the false acacia tree because it looks very similar to the Honey locust tree. The younger shoots, branches and suckers can be covered in spines which can easily tear clothes - so be careful!
Black Locust usually reach heights of 12–30 meters but there have been some that have reaches heights of over 50 metres! They are usually fairly straight and upright trees and older trees tend to have a more untidy crown. It is a shade-intolerant species so will only establish itself in disturbed areas with plenty of open space or young woodlands. Outside of America it is often considered a weed species due to the fast growth rate and the the intense root suckers it can send out. If the tree is damaged (land-mowers for example) or removed completely then it will send out hundreds of root suckers which if left unchecked will grow into small trees.
The bark is deeply furrowed and reddish, black and grey and tinged with red or orange in the grooves. The ridges that run up and down the trunk sometimes form diamond shapes or criss-cross patterns. The branches are zig-zagged and when young covered in a silvery down which soon disappears. The spines can pose a problem as they can easily snag or tear clothing. No two trees are alike so one Black locust can be covered with spines and another have next to none at all. The roots are nitrogen fixing which helps improve the soil quality.
The fruit (pods) remain on the tree for a long time and are easily seen during the winter time
The white flowers bloom during May / June and are a favourite of bees
The leaves are arranged alternatively and are 15–36 cm in length and usually contact 9-19 leaflets. The leaflets are slightly rounded and pointed towards the tip. During the Spring and Summer the leaves are a dull green and during the Autumn they turn light yellow. The leaves appear relatively late in the Spring.
During May - June the tree will be in flower, however the flowers only last a short time. They tree is transformed when in full flower and really stands out, The flowers are arranged in loose drooping clumps called racemes and are a favourite of bees as they produce a lot of nectar. The flowers are creamy white with yellow blotches and rely on insects to pollinate them. The flowers are perfect so each one has both male and female parts contained within each flower. The fruit is a flat and smooth pea-like pod around 5 to 10 cm in length. Inside the pod there are usually 4 to 8 seeds. All parts of the tree are considered toxic except for the flowers. The flowers are fragrant and used to sweeten dishes. In America the flowers are used to make a type of fritter.
OTHER USEFUL LINKS
- Black locust was introduced into the UK in 1636
- It can live between 60 - 100 years in parks and green spaces but up to 300 in it's natural habitat
- It is native to the eastern part of America - outside of this it is usually considered an invasive species
- In America they are used for both construction and also ornamental purposes
- In the UK they are typically planted in parks and green spaces
- Due to the intense root suckering they do not make good street trees
- They are a fast growing species and in some cases can grow up to 1 metre per year
- Most Black locust trees will have spines to help protect against browsing herbivores
- The spines can get quite big and easily snag and tear clothes
- The wood is very strong and rot resistant which is why it is was so heavily used in America for construction
- The leaves are arranged alternatively and are 15–36 cm in length and usually contact 9-19 leaflets.
- The flowers are insect pollinated and a favourite of bees
- The flowers are creamy white with yellow blotches and are also fragant
- The flowers are perfect so each one has both male and female parts contained within each flower
- The fruit is a flat and smooth pea-like pod around 5 to 10 cm in length.
- Inside the pod there are usually 4 to 8 seeds
- All parts of the tree are considered toxic except for the flowers
- The flowers are edible and very sweet. A popular dish is 'Black locust fritters'
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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 Locust the better. Many thanks!