The black locust or false acacia

The black locust or false acacia, known by its scientific name Robinia pseudoacacia, is an exotic plant that was introduced from North America in the 17th century. This tree, which can reach up to 25 metres in height and live for as long as 300 years, has spread easily throughout Switzerland, as it adapts to all types of soil and is resistant to pollution, to the point of sometimes being considered invasive; however, it is not found above 800 metres in altitude.

The leaves have up to ten pairs of leaflets and two large thorns at their base. The white flowers are arranged in beautiful, pendulous clusters and are highly fragrant.

It is a very nectar-rich tree that flowers at the end of May or at the beginning of June. Although it is very hardy in terms of establishment, its flowering is nevertheless capricious and depends on specific climatic conditions: absence of late frosts, thunderstorms and cold winds; moist soil; warmth; high atmospheric humidity.

The black locust gives rise to a very mild honey, most often marketed under the name “acacia honey”, although it should more correctly be called “black locust honey”. Thanks to its high fructose content, it remains liquid for a very long time; when it is pure, that is, not “contaminated” by other nectars, it is almost transparent.

In Switzerland, it is mainly in Ticino that a mono-floral black locust honey can be obtained; even though it represents the most important spring nectar flow there, it is very rarely completely pure, as it is most often mixed with other plant species flowering at the same period.

The pollen is greenish in colour and is highly appreciated by bees. However, black locust produces only small amounts of pollen, which means that it is under-represented in honey, that is, only small quantities are found even in pure honey: a proportion of just 10% black locust pollen in honey is already sufficient to classify it as mono-floral honey of this species!

Sources

Silberfeld, C. Reeb, Melliferous plants, 2016

Agroscope, Important sources of pollen and nectar for honey bees in Switzerland, 202

Piquée, Melliferous plants month by month, 2014

Various authors, The Rustica beekeeping handbook, 2002

Various authors, Beekeeping, a fascination, Vol. 4, Beekeeping products and apitherapy, 2014