The chestnut tree

Castanea sativa Miller is the scientific name of the chestnut tree. It is a majestic, long-lived tree that can reach up to 40 metres in height and 15 metres in circumference. As it does not tolerate calcium and its salts, in particular carbonates (limestone), it is found on acidic soils; this explains why it is not evenly distributed in Valais.

The leaves are large (up to 30 cm long and 10 cm wide) and deeply serrated. Like all monoecious species, male and female flowers are separate but borne on the same plant. The male flowers consist of long, pale yellow catkins grouped in clusters at the ends of the branches. The female flowers are much more discreet, small and rounded, and located at the base of the male catkins; after fertilisation, they develop into spiny burrs enclosing the chestnuts. At full bloom, in June–July, chestnut trees resemble a fragrant and spectacular firework display.

The chestnut tree is pollinated mainly by wind; however, bees, attracted by the very strong scent of the flowers, actively collect its pollen (yellow-green in colour), which is of high value due to its rich content of proteins and essential amino acids.

The chestnut tree produces abundant nectar with a high sugar content, as well as honeydew. In Ticino, it represents the main summer honey flow and provides—when not mixed with linden, which flowers at the same time—a monofloral honey with a strong, slightly bitter and very characteristic taste. This dark-coloured honey remains liquid for a very long time.

Because the anthers (the pollen-producing and pollen-releasing parts of the male floral organ) directly overhang the nectaries, chestnut nectar contains a large amount of pollen, which is therefore overrepresented in the honey. This pollen, easily transported by wind, complicates pollen analysis of other honeys, as a honey may contain up to 95 % chestnut pollen without actually being a chestnut honey.

In the past, chestnut wood also had an application related to beekeeping: its trunks were used to make hives, known for example as “bugni” in Ticino and “bruscs” in the Cévennes region of France (Isabella Moretti).

Sources

Silberfeld, C.; Reeb, Les plantes mellifères, 2016

Agroscope, Important sources of pollen and nectar for honey bees in Switzerland, 2020

Piquée, Les plantes mellifères mois par mois, 2014

Bieri, S.; Bogdanov, L’apiculture – une fascination, Vol. 4: Hive products, 2014

Bieri, Pollen analysis of the BIP (Biologisches Institut für Pollenanalyse), 2016

Swiss monofloral honeys, Alp Forum 2005, No. 23f (reprint 2008)

Sofia, Le voci – Castagna, Extract from the Dictionary of the Dialects of Italian-speaking Switzerland, 2001

Various authors, Le traité Rustica de l’apiculture, 2002