Almond Tree Blossoms
Almond Tree BlossomsJonathan Cardy

The beautifully-blossomed almond tree which features prominently in Israeli celebrations of Tu b'Shevat has a dark side. Nectar of almond flowers contains 4-10 milligrams per liter of amygdalin, which yields the potent poison cyanide.

While sweet almonds are safe for eating (though causing an allergic reaction in some people), wild bitter almonds also contain amounts of amygdalin and could be toxic, especially for young children.

A group of researchers at the Department of Environmental and Evolutionary Biology and the Department of Science Education at the University of Haifa-Oranim set out to investigate why the almond tree produces poison, especially when the purpose of flower nectar is to attract bees, which will pollinate them.

They discovered that the lethal substance is actually there to give the lushly-flowered tree an advantage over nearby competitors.

Bees like the toxin

Professors Ido Izhaki, Gidi Ne'eman, Moshe Inbar, Dr. Natarajan Singaravelan and their team exposed honey bees to plates of nectar that had varying concentrations of the toxin and a plate of nectar without the toxin. The team first monitored four different amygdalin concentrations in the range of the natural levels of toxin typically found in almond tree nectar. A second experiment monitored levels much higher than those found in the natural form.. In all cases, the bees preferred nectar containing amygdalin over the amygdalin-free variety.

It turns out, according to Professor Izhaki, that while amygdalin is poisonous for mammals, it is not poisonous for insects, such as the honey bee. In fact, it may act as a stimulant which attracts them.

Another theory is that "expert" bees – ones who have been pollinating for some time – will have built up a tolerance to amygdalin, resulting in the arrival of only the most seasoned pollinators at the almond tree.

The research team is also examining the possibility that the nectar toxin prevents bacteria from harming the nectar and threatening the pollination of the tree.

The almond in the Tanach (Bible)

The relationship between the Jewish people and the tasty almond is traced back to the Torah.  Almonds were among the produce of the Land of Israel presented by Jacob to the Egyptian Pharoah via his sons in Genesis 43, when they went down to Egypt to buy food during the famine in Canaan.

When leadership roles were being clarified, the staff of Aaron sprouted almond buds to show that he was chosen by G-d in Numbers 17. Jeremiah also was shown an almond branch by G-d in his first prohpetic vision (Jeremiah 1).