1Robinia

Robinias are deciduous trees with rounded crowns that can reach heights between 20 and 30 meters, depending on whether they are solitary or in groups. Robinias have a thick, gray-brown and deeply furrowed bark. They are hardy and do not become green until late spring.

The trees owe the name false acacia or pseudacacia to their shape. The bark, which looks as if it has been plaited, along with the pinnate leaves and thorns are reminiscent of acacias, to which, however, the robinia is not related. The name robinia comes from Carl von Linné, who first described the genus. He named it after Jean Robin, the French pharmacist, botanist and court gardener who introduced robinias from Virginia in 1601 because of their inflorescences. Between May and June, the trees display white stalked flowers. One to two dozen of these form pendulous inflorescences about 10-25 cm long on young twigs that smell of bergamot.

In 1670, the robinia was first cultivated as an ornamental tree in Germany, in the Berlin Lustgarten. Nowadays it also grows wild in Germany. It has low soil requirements. As a legume, it even fertilizes itself by carrying nodule bacteria on its roots that bind atmospheric nitrogen. It is therefore also cultivated to reforest forests that have been destroyed by overuse. In addition, it can also reproduce vegetatively through root sprouts. On top of that, its fruits are special. The pulses, about five to ten centimeters long, bear about four to twelve seeds each. They are ripe in September, but remain on the tree during winter and all the way until spring in some cases. The seeds are still capable of germinating after up to 30 years. These characteristics make robinias prone to go wild, as seen in Germany. Here, after World War II, it spread widely in rubble fields, on land that was destroyed and not maintained.

Today, the robinia has a permanent place in beekeeping. Its flowers provide abundant nectar, whose high sugar content attracts many insects. Most of the acacia honey sold in Germany actually comes from robinia. It is popular because of its liquid consistency. Because it contains a lot of fructose and little glucose, it does not tend to crystallize. In Brandenburg, this accounts for up to 60 percent of the honey harvest.

The flowers can be processed into jam or syrup or used in teas and drinks. On top of that, they contain substances that are said to have health-promoting effects. Flavonoids such as acaciin are interesting for Alzheimer's therapy because of their possible neuroprotective effects. Farnesol has an antibacterial effect and is being discussed for potential uses in cancer therapy.

The bark and fruits, on the other hand, are highly toxic. They contain toxic proteins like robin and phasin, and glycosides like syringin and tannins. Robin and phasin cause the blood to clump (agglutinate). Poisoning is manifested by nausea, abdominal pain, vomiting, and elevated body temperature. Dizziness, fatigue, and sleepiness are accompanied by dilated pupils, visual disturbances, and convulsive twitching. Circulatory problems, collapse and death are possible.

In 2020, the robinia was Tree of the Year in Germany.