There are significant differences among the various chestnut tree species’ growth rates: there are species with strong, medium, or weak growth rates, affecting the shape of the crown. At a young age - before they become mature - trees with a strong growth rate have an upward shooting crown, but their shapes can significantly change as the trees age. For instance, a crown that is cone-shaped at a young age can turn into a sphere or spread-out mushroom shape. At the more serious plantations, professional shaping and pruning can significantly alter the height and shape of the crown in a way that is characteristic of that particular species of chestnut tree. During pruning, however, the trees’ basic characteristics must be taken into account. These considerations especially apply to the trees’ tendency to develop thick foliage.
The shooting of the chestnut tree occurs relatively late, between
mid-April and early May with as many as 20-25 days of delay among the different species. In order to avoid spring frost damage, it is expedient to plant later-shooting species in low-lying, frost-risk areas.
Chestnut trees bloom in late June and early July, well after the period frosts are most damaging. Blooming time is the most significant difference among the different-sex flowers, i.e. to what extent pollen dispersion coincides with the blooming of the tree’s own female flowers.
Time of ripening
The ripening time of certain chestnut species lasts from the end of September to the beginning of November. Chestnut species, which ripen early, are more valuable due to their high prices at the pre-season market; at the same time, those which ripen late can also be valuable due to their easy storage. The very late species, however, can be unprofitable because of their uncertain ripening; hence, it is
not expedient to plant these species in frost-risk, low-lying areas.
Means of ripening
There are also significant differences in their means of ripening. There are certain species, of which hulls open up evenly during ripening, with all the perfectly ripe nuts falling out of the hulls at the same time. At the other exreme, the hulls do not even open up but fall off the tree, and need to be opened during harvest. There are all sorts of combinations between these two extremes. The most efficient species is the one of which hulls open up evenly, because their harvest is the easiest. Nevertheless, the species with the closed but ripe hulls can also be split open with simple tools, and their storage can be very efficient.
Process of ripening
From a profit perspective, the process of ripening can also be significant; that is, how long it takes for all the fruits to ripen. Depending on the species, this usally takes place
between 10-30 days. With regards to harvest coordination, the most profitable species are those that have the shortest ripening process.
Regarding life-span, coloration, and defoliage during the fall season are important characteristics. These features are connected to the growth time of the species, and there are great differences in it among the species. The foliage of those species with a short growth time becomes yellow in early spring and falls down, while those species with a long growth time become dark brown when the early morning frosts arrive in the fall, but they only fall to the ground when the strong winds arrive in early winter. With regards to ripening, the fast-ripening, evenly colored, and deciduous trees are the most profitable. These characteristics can be considerably affected by diseases and the variations in fall wheather each year.
A characteristic that most influences
productivity is the number of nuts in a cupule. This can vary between one and seven, and there is a strong relationship between this feature and the size of the fruit. In case of certain better species, there are one to three nuts in a cupule. However, in a three-nut cupule, the size of the middle nut is not adequate, because both of its sides are flattened. Another characteristic influencing productivity is the grouping of the fruits; that is, how many cupules are on one fruit-producing twig, and how frequent they are.
With regards to productivity, the most important feature of the chestnut tree is the percentage of shoots that actually hold fruits. The productivity of the species is connected to this characteristic.
Productivity changes with age. In this respect, there is also a difference between artificially fertilized trees and saplings grown from seeds.
Chestnut trees, grown from seeds, reach their age of productivity
within 12 to 20 years. In contrast, graftings are already at a physiologically mature age, and can even produce fruits within a year of being planted; their yields increase simultaneously with crown expansion.
Seedlings, which produce about three kilograms of fruits at the age of 8-15, should not be considered mature yet; certain trees in mixed stands show their first fruits earlier.