The sweet chestnut (Castanea sativa) is a species that originated from South Europe and Asia Minor. The sweet chestnut can be used for decorative purposes, or for its wooden mass. Over the course of last years, the interest of growing the sweet chestnut as a crop has increased because of the sweet chestnuts’ nutritional content. Their properties are similar to those of the wheat seeds. The sweet chestnuts contain starch, vegetal fibers, protein, fats, potassium, phosphorus, magnesium, sulfur, calcium and vitamins (A, B1, B2, E, C).
Growth and fruition requirements
The sweet chestnut can grow as a vigorous tree, 15-25 m high. The trunk is vigorous and slightly bended and the tree grows wide, pyramidal, globose crowns. The tree’s structure branches are vigorous and well garnished with twigs. It grows vegetative or mixed buds. These are solitary placed on the branches. The leaves are serrated and elongated (lanceolate) and can reach a length of 28-cm. The sweet chestnut is a unisexual – monoecious species. The same tree grows both male and female flowers. The female flowers are 2-3 per involucre, and as the flowers mature, their appearance resembles the one of a hedgehog. The male flowers can grow more stamen types, but the most productive species are the ones that have longer stamen filaments. The sweet chestnut can also grow aments, that are bisexual flowers. Their length is around 30-cm. The female flowers are grouped in inflorescences and located on the lower part (base) and the male flowers are located on the upper part. The fruit is an achene. Its color is a reddish brown and it can contain one or two seeds.
Climate and soil requirements
The temperature is a restricting factor for the edible sweet chestnut crop. It can only grow and normally develop in areas where the average annual temperatures exceed 9 degrees Celsius. It prefers long and warm autumns, it is sensitive to sudden frosts. During the vegetative rest period it can tolerate temperatures as low as -25 degrees Celsius. The light is not an important factor for this species. It can also grow well in semi-shady spots. It needs around 700 mm of rainfall per year, evenly spread across the vegetation period. On the other hand, it doesn’t tolerate the excess soil humidity and the ground water must be at least 4-m deep into de ground. It prefers fertile, deep soils, that have a high air-water regime and an acid pH (4.8 – 6.5).
Choosing and preparing the soil
The parcels where the sweet chestnut plantation will be started need to be chosen depending on the climate and soil requirements of each species. The most favorable areas for growing this species are the hills, or any other areas where the chestnuts naturally grow. The soil preparation procedures are similar to those of any orchard species. The parcel must be cleaned of the previous crop and of all vegetal residues (including the underground ones). After this procedure, the soil must be levelled and base fertilizers can be applied (organic compost, 40 tons per hectare). The fertilizing process can be supplemented using 100 kg/ha of phosphorus, active substance and 80 kg/ha of potassium, active substance. The fertilizers must be incorporated into the soil using a deep plough, 30-35-cm deep and thn the disk cultivator must be run over the parcel twice.
The optimum planting period is during the autumn season, when the trees have entered their vegetative rest period. The following planting schemes are recommended: 9-m distance between the rows and 8-m distance between the plants on each row. After establishing the planting scheme, the parcel must be marked. The operation consists of placing a stake into the soil where each plant should be. Use 2-3 sweet chestnut species to have an optimum pollination. The following processes to be done are: the digging of the holes and the actual planting. The holes can be manually dug, or using the drilling tractor. The dimensions on the holes must be: 40 x 40 x 40 cm.
Before planting, the roots must be cleaned up. The purpose of this process is to remove the wounded parts of the roots and to smooth the existing roots. This process will also rejuvenate the root system. The dead roots must be removed and the living ones must be shortened and left at a 20-22-cm length. After cleaning the roots, these must be mulched. Mulching the roots represents placing them inside a mixture of yellow soil, cattle organic compost and water. The mulching layer will help the trees better adapt to the new environmental conditions. It is recommended that the mulching mixture has a sour-cream like consistency. The most common edible sweet chestnut species are: Romval, Casval, Tismana, Precoce Migoule, Maraval, Marsol, Iza, Mara, Hobita, Polovraci, Gureni, Prigoria.
The distance between the tree rows must be planted with grass. The Lolium perenne species is recommended, but seeds must be sowed once every 4 years. The grass must be mowed once it has reached a length of 5-10-cm and it must be put back on the soil to act as a mulching layer. The distance between the rows must be kept clean by repeatedly ploughing, or by applying herbicides. The following products can be used: Frontier Forte EC, Stomp Aqua, Roundup Clasic Pro, Taifun 360 SL, Dual Gold EC.
Supplementary fertilizing is necessary for the commercial plantations. To correctly establish the needed fertilizer dosage, agricultural and technical analysis must be performed on the soil and plant. The general practice is to annually apply 60kg/ha of active nitrogen and 80 kg/ha of active potassium. The fertilizers also increase the plant’s resilience to diseases and pests, to the environmental conditions and prolong the plant’s life. Besides fertilizing, another method which provides important production increases is the irrigation. The crop must be irrigated when the annual rainfall does not come up to 700 mm per year. The most efficient irrigation system that can be used are the micro-sprinklers and the drip irrigation.
Preventing diseases and pests
This is a necessary step for the sweet chestnut crop. For more information about the diseases and pests that can affect this crop, as well as the proper prevention means, please search for the relevant article on our website.
Another important maintenance operation that can be performed is to periodically cut the trees. The sweet chestnut tree doesn’t need vigorous cuts as it naturally grows a well aired crown. One thing we should all consider is the placement of the fruit-bearing sprouts. When it comes to planting the edible sweet chestnut in Europe, bear in mind that these sprouts are located on the superior sides of the branches. This way, the sprouts will not fall down annually as cuts will have to be applied only against old branches. This is how the tree will grow new branches. You must also take out the greedy, dried or frost affected branches, as well as the suckers. When doing this, keep in mind that that crown must be aired and the branches must be evenly spread.
The optimum harvesting period is visible as this is when the fruits will fall from the tree. By looking at the calendar, this period is between the 20th of September and the 15th of October. Harvesting the sweet chestnut is a difficult technological operation as the fruit are closed inside an involucre and after harvesting, this shield must be removed. The harvesting step can be done by manually of mechanically shaking the trees. The harvesting cost represents 40% of the annual crop cost.