Common names: Sweet Chestnut (also called Spanish Chestnut) 

Irish name: Castán 

Latin name: Castanea sativa 

Family: Fagaceae 

Origin: non - native 

Tree type: Deciduous broadleaf tree

How it looks

Shape, bark, twigs 

Castanea sativa is a large, fast growing deciduous tree which belongs to the same family as Oaks and Beeches. Its mature height can be up to 35 metres and trees can live for up to 700 years. Its bark is smooth and purplish grey in colour when young, brown and furrowed when mature.

Buds

The buds are alternate and present as red-brown and oval in shape. The lenticles are swollen below the buds.

Leaves 

It has a long, slender, glossy leaf with serrated or jagged, deeply toothed edges which turns golden yellow before falling in Autumn.  

Flowers 

In late June - July, there are catkins/flowers up to 20cm in length which bear the male flowers at the tip and female flowers at the base. When Autumn comes, the female flowers develop into the chestnuts. It develops spikey yellow flowers/catkins in summer.

Fruits 

Reddish brown nuts which occur in clusters are found in a prickly case in the Autumn, before dropping to the ground as they ripen. These nuts are edible and are associated with Christmas. These are not to be confused with conkers, which are the inedible fruits of the horse chestnut, Aesculus hippocastanum tree.

Where to find it

Sweet chestnut is native to southern Europe, western Asia and North Africa.  It has been widely planted in Ireland. It was introduced here in the 17th century and has therefore become very well established.  It can be found in parks, large gardens and estate woodlands.

Cultural importance

There is evidence to suggest that sweet chestnut was being cultivated in Greece over 4000 years ago. Based on the writings of the naturalist Pliny the Elder, it has been proposed that the tree was introduced to Greece from Asia Minor as early as 5000 BC. However, the spread of the sweet chestnut throughout Europe is attributed to the Romans, amongst whom the tree and its nuts were popular. Ancient texts indicate that the Romans first cultivated the sweet chestnut for its timber, but sweet chestnut flour is thought to have been a staple of the Roman army.  

As it spread throughout Europe, the sweet chestnut became a popular source of food, so much so that in certain regions such as southern Switzerland, it earned the title, ‘bread of the poor’. 

Sweet chestnut was introduced as a food source to the British Isles by the Romans. For many years it was believed that the Romans were the first to cultivate sweet chestnut in Britain. However, recent palaeobotanical research from Britain indicates that while the nuts of the tree may have been brought to Britain during the Roman period, the sweet chestnut was not grown there before c. 650 AD. Indeed, the oldest surviving sweet chestnut in Britain dates to c. 1640 AD. Accounts suggest that the sweet chestnut was also introduced to Ireland around this time.  

The robustness of the sweet chestnut tree has led to the preservation of numerous ancient specimens across Europe. Among them, the ‘Hundred Horse Chestnut’, situated just 5 miles from Mount Etna's crater in Sicily, stands as the largest and oldest known chestnut tree globally. With a circumference nearly 60 meters wide, it is estimated to be between 2,000 and 4,000 years old. According to legend, during a fierce thunderstorm, Joan of Aragon, Queen of Naples, and her retinue of 100 mounted knights sought refuge under this tree, hence its name ‘hundred horse’.  

Some beautiful examples of veteran sweet chestnuts in Ireland can be found at Cranmore in Belfast, Muckross House in Killarney and Woodstock Gardens Inistioge, Kilkenny. The sweet chestnut at Rossanagh, County Wicklow is another good example. In 1733 it was pronounced to be largest tree in Ireland. Furthermore, it is thought to be one of the oldest trees in Wicklow, under which the Methodist preacher, John Wesley, gave a sermon in 1789. 

Myth, Legend and Folklore 

Due to its value as a food source throughout history, the sweet chestnut has come to symbolize abundance, fertility and longevity. Similarly, in some cultures, it was believed to help women conceive. In ancient Greece, the sweet chestnut was associated with the God, Zeus.  

Literature 

In the Charlotte Brontë novel, Jane Austen, the motif of the sweet chestnut is used to symbolize strength and stability. 

Value to wildlife

The sweet chestnut is very good for biodiversity. The flowers offer a crucial supply of nectar and pollen for bees and various insects, whereas red squirrels rely on the nuts as a food source. Additionally, numerous micro-moths consume the leaves and nuts as part of their diet.

Threats

Chestnut weevil can cause damage to the fruit. There are two major threats to the sweet chestnuts: the oriental chestnut gall wasp (OCGW) and a fungus, chestnut blight. The OCGW lays its eggs inside a tree’s buds, which causes galls – abnormal growths – to appear, and reduces its ability to produce nuts. The fungal disease chestnut blight can eventually kill a tree, causing cankers on its bark. Both are quickly spreading across Europe.

Uses

It is a versatile species offering both timber and sustenance. The nut or chestnut can be ground to make a flour, similar to polenta. It is traditionally roasted and used at Christmas time. The wood of the sweet chestnut is very durable, hard and strong and because of the tree’s natural resistance towards decay, the wood of the sweet chestnut is particularly suitable for external use. Uses include barrel making, furniture production, fencing, posts and stakes.

References

Dublin Garden Trail. 2024. The Dower House, Dublin Garden Trail Website. Dower House | Dublin Garden Trail (dublingardengroup.com) 

Current Archaeology. 2019. That old chestnut: how sweet chestnuts came to Britain, Current Archaeology Magazine. That old chestnut: how sweet chestnuts came to Britain - Current Archaeology 

Forbes, A.C. 1932. Tree planting in Ireland during four centuries. Proceedings of the Royal Irish Academy. Section C: Archaeology, Celtic Studies, History, Linguistics, Literature, 41, pp.168-199. 

Jarman, R., Mattioni, C., Russell, K., Chambers, F.M., Bartlett, D., Martin, M.A., Cherubini, M., Villani, F. and Webb, J. 2019. DNA analysis of Castanea sativa (sweet chestnut) in Britain and Ireland: Elucidating European origins and genepool diversity. PLoS One, 14(9), p.e0222936. 

Mabbett, T. 2020. Sweet chestnut: The host of pests and diseases that threaten the species today, Forestry Journal: Essential ARB. Sweet chestnut: The host of pests and diseases that threaten the species today | Forestry Journal 

Magner, D. 2017. Sweet chestnut – an underrated species, Irish Farmers Journal.  Sweet chestnut – an underrated species - Premium (farmersjournal.ie) 

Monumental Trees. N.d. Sweet Chestnuts (Castanea sativa) in Ireland, Monumental Trees, Sweet Chestnuts (Castanea sativa) in Ireland (monumentaltrees.com) 

Rankel, K. 2024. Symbolism and Benefits of the Sweet Chestnut, Greg Website. Symbolism and Benefits of the Sweet Chestnut (greg.app) 

The Heart of England Forest. N.d. Sweet Chestnut, The Heart of England Forest. Sweet chestnut | Heart of England Forest 

Woodland Trust. N.d. Chestnut, Sweet (Castanea sativa), Woodland Trust Website. Sweet Chestnut (Castanea sativa) - Woodland Trust