Sweet chestnut - a tree for grower and gourmet

By Donal Magnier

Sweet chestnut has adapted well to Irish conditions over the centuries. It grows to a massive size given the right conditions: the greatest girthed broadleaved tree in Ireland is the John Wesley Tree, a chestnut near Ashford, Co Wicklow which has a girth of 35 ft (10.6 m). It can also achieve excellent height growth: a sweet chestnut in the Queen's Drive, Muckross, Killarney is over 30m.

Nobody is sure when it arrived in Ireland. It is likely that the Romans introduced it to Britain sometime during the period 100BC to 450AD and some believe that it was introduced to Ireland by the Normans.

We know that it was certainly growing in Ireland in the 17th century as the records show that it was well established as early as 1625 according to the writings of O'Sullivan Beare. Also known as Spanish chestnut, it is a Mediterranean species and a number of places lay claim to its Latin name - Castanea sativa - including the ancient city of Kastanaia in Asia Minor (modern Turkey) and the towns of Castanea and Castana in Greece.

Establishment

It grows well in a variety of sites in Ireland but it is well to avoid exposed or frosty sites. It doesn't like extremes - very wet and very dry soils. It needs shelter and while it won't thrive on nutrient poor soils it will do well on moderately fertile light soils. It should be planted at 2.0 x 1.5m spacing or a stocking of 3,500 per hectare. It is relatively easy to establish as it grows fast during the first few years. It responds well to chemical weed control and it is unlikely to require fertilizer application if planted on moderately fertile soils although phosphate application may be necessary.

Maintenance

On sheltered sites it should require very little formative shaping or pruning. However, the grower should aim to have at least 400 good stems per hectare as straight knot-free sweet timber has a wide variety of high quality end uses.

Planted on the right site, sweet chestnut is windfirm and is relatively disease free although the threat of chestnut blight - currently causing damage in southern Europe - cannot be ruled out.

Rotation and end uses

Sweet chestnut has a long life. There are plenty of examples of trees that are well over 200 years old in Ireland. However, as it grows old, it develops spiral grain and a condition known as shake, which manifests itself as cracks in the timber. The grower can opt to have fine specimen trees such as the John Wesley tree but if the objective is to produce good quality sawable wood, then a rotation not greater than 80 years is recommended.

The wood is excellent resembling oak in a number of respects; not quite as strong but easier to work. It is used for furniture and flooring and clean knot free lengths are used for veneer.

It makes excellent fencing posts and providing the wood is dried properly, it will last for 25 years without preservation. If the logs are ponded or immersed in water they can last up to 40 years.

Culinary chestnut

The tree has been valued on the continent as much for its edible nuts as its wood. Our gourmets have largely ignored the fruit and while our climate is not always obliging in producing good crops, there have been excellent seed years. The nuts can be boiled or roasted and also used in savoury and sweet dishes.

I remember a forest worker in Piltown, Co Kilkenny - the late Billy Breen - used to collect the nuts in the Mountain Grove, which his mother used for a variety of dishes from stuffing to stews. In the list of Champion Trees produced by the Tree Register of Ireland it appears as a fine specimen tree not only in the aforementioned Ashford and Muckross, but right around the country.

Champion trees are located in places as diverse as Scarva, Co Down, Johnstown Castle (29m in height), Bunratty, Ballinasloe, Lough Key, the Malone Road, Belfast, Borris, Cappoquin, and Williamstown, Co Meath. Sweet chestnut is now an honorary native species in Britain and while it is unlikely to achieve that status here, it deserves a more prominent place in Irish forestry.