Fruit and Nut
The edible chestnut - Castanea sativa - usually referred to as the Spanish or Sweet Chestnut, is a native of mountainous regions of Western Asia, North Africa and Southern Europe. The earliest record of chestnut cultivation is in Theophrastus' Enquiry into Plants, written in the 3rd century BC. However, pollen analysis from Insubria, the lakes area on the modern day Swiss-Italian border, shows Castanea sativa to be present from 10,000 ago onwards. During Roman times, chestnut cultivation took place in Insubria. The Romans are thought to have introduced the chestnut to Northern Europe, including Britain.
Chestnut cultivation became common in many European countries during late Roman times and the Middle Ages. For a while, part of the Italian-Swiss Alps became known as the chestnut civilisation. Across Europe, many individual cultivars were developed, some specific to one or two small valleys. In mountainous areas unsuited to tillage, chestnuts provided a viable alternative to grain and became a staple part of the diet. Chestnut cultivation in Northern Europe was often carried out by religious communities and monastic orders.
Globally, a number of close relatives of Castanea sativa are cultivated for nut production. These include, C. crenata (Japanese chestnut), and C. mollissima (Chinese chestnut). The main European producers of the chestnut are Italy, Spain, Portugal and France. However, the chestnut is also grown in many other European countries including Germany, Austria, Switzerland and Poland. Reported yields are 1-5 tonnes per hectare. A good individual tree may yield up to 25 kg per year. Chestnuts are more tolerant of high rainfall than walnuts and can be found thriving in many parts of the Alps and northwest Spain, where annual precipitation often exceeds 1000mm.
Chestnuts are a major food crop in regions where they are grown. The nuts are normally not eaten raw but used baked, boiled, roasted or in confectionary. Chestnuts have also been used to make flour and for animal feed. Compared to other nuts chestnuts are low in protein and especially low in fat. Carbohydrate content is relatively high at 32 percent. Water comprises 40 percent.
Chestnuts contain a wide range of vitamins and minerals. Average content per 100g is as follows:
Vitamin C 26 mg (considerably more than in most apples)
Named varieties of the Spanish Chestnut (Castanea sativa) are suitable for growing in the south, midlands and east of Ireland, and in favourable locations elsewhere. Viable nuts recently found under mature trees growing near Westport, Co. Mayo, confirms that Spanish chestnuts have the potential to do well in the west of Ireland, as well as in the drier south and east.
The named varieties - the products of hundreds of years of careful selection by growers - perform significantly better than either Castanea sativa grown from chestnuts or unnamed varieties of Castanea sativa obtained through conventional tree nurseries, and will begin cropping at a young age. Although Castanea sativa grown from seed will grow into a fine tree in Ireland, flowering does not usually commence for 15-20 years. Trees grown from randomly selected seed are unlikely to set fruit in Ireland on a regular basis.
All the varieties offered here begin cropping at a young age and have been chosen for their earliness of ripening and good performance in the west of France (the chestnut-growing region most similar to Ireland). Two or more varieties are normally essential for good pollination.
Chestnuts prefer a deep, well drained, loamy but slightly acid soil. They are intolerant of poor drainage, heavy clay and alkaline soils. Cold or wet weather at flowering time (mid June to mid July) can lead to very poor pollination. However, the presence of plentiful bees and other insects will improve the outcome. For this reason, it is recommended that chestnuts are underplanted with flowering plants - clovers or other legumes for example - known to attract bees.
Mycorrhizal fungi are special fungi that have a symbiotic relationship with the roots of a plant. The very large surface area and specialised cell membrane chemistry of the fungi mycelium allow the colonised plant to access water and soil nutrients much more efficiently, leading to stronger growth and greater resistance to disease. Mycorrhizal fungi are found on the roots of trees in almost any mature woodland , but are usually absent on the roots of young trees raised in nursery conditions. Chestnut trees innoculated with mycorrhizal fungi have been shown to have much greater resistance to Ink Disease (Phytophthora cinnamomi and P.cambivora), a debilitating fungal infection responsible for the demise of some chestnut orchards. Proprietary root-dipping gels containing mycorrhizal fungi can be purchased from specialist horticultural suppliers. Alternatively, a small amount of leaf litter can be collected from broadleaved woodlands where wild mushrooms - Gyroporus castaneus and Boletus edulis for example - are known to be common, and sprinked around the bare tree roots during planting. For more information on mycorrhizas, refer to the Agroforestry Research Trust booklet on chestnuts.