Almonds are supposed to bloom on Tu Bashvet, which falls at the end of January/beginning of February, but in recent years they have been doing it as early as October. The pollinating bees did not have time to prepare at all, and this lack of coordination harms not only the trees and the bees but also us
Inbar Stutman, Angle - Science and Environment News Agency
Almond blossoms (early)
January 25, 2016
In the middle of winter, around the month of February, comes one of the most favorite days of the children of Israel - Tu Beshvat. They leave the gardens and schools and plant trees in the areas outside the city, all the way looking for flowers that hint at the spring that will come soon.
The tree associated with Tu in the tribe is a common almond, which is common in the Mediterranean basin. The almond has abundant and dense pinkish-white blossoms, and the Jewish tradition attributed a special role to it in the holiday of the New Year due to its relatively early blossoming compared to other fruit trees.
The almond blossom appears in the months of February-March and remains on the tree for only a month and a half, but in recent years you can see trees full of flowers as early as October. So although the almond blossoms, the sun does not rise at all because winter is just beginning. What is the cause of this phenomenon and how problematic is it?
leaves a bitter taste
The reproduction of flowering plants usually depends on the distribution of the pollen produced in the stamens by a foreign agent such as wind, birds or insects. These are attracted to the flower because they feed on the pollen or nectar it produces. That foreign agent collects what it needs, and in the process distributes to other flowers the pollen that has stuck to its body (spreading the plant's male DNA), thereby ensuring the continuity of the species.
Prof. Dan Izikovitz, an almond pollination expert from the Faculty of Life Sciences at Tel Aviv University, explains that the one responsible for the fertilization of the almond is the honey bee because, unlike other bee species, it does not hibernate. The reproductive organs of the almond flower are inside it and the structure of the flower is one that requires a bee, so the cooperation benefits both parties.
The wild almond trees that grow in Israel are cultural refugees, explains Prof. Izikowitz, that is, trees that were cultivated in the past and spread back into the wild, and are characterized by the bitterness of the nectar and the fruit. The source of the bitter taste is cyanide - a toxic compound found in some citrus fruits, such as apricots and apples, and it probably protects against pests. "The cyanide also affects the functioning of the main pollinator of the almond, the honey bee," says Prof. Izikovitz. "Since the nectar is bitter and contains the poison, the bee takes very little of it each time and therefore has to visit a lot of flowers to meet its collection quota."
The Israeli winter is characterized by relatively favorable weather conditions, and at a temperature of about 14 degrees Celsius the bees can work to obtain the nectar they need. Since the beginning of winter is not a flowering season and few plants bloom during this period, the almond has a competitive advantage in attracting pollinators.
"The blooming of the almond is possible as a result of the accumulation of cold doses, and if it has not accumulated a minimum of these, or if there were too many, disruptions are caused in the time of flowering and its quality," says Prof. Izikowitz. Early flowering is very problematic for bees because they are not active in the rain, and if it rains for one week during the flowering period which is not long anyway, the pollination is not effective enough.
Not only the cold affects the blooming dates of the almonds but also the development of stress due to lack of rain. Prof. Marcelo Sternberg, an ecologist who specializes in climate change and its effect on plants, says: "Usually plants in a state of stress precede flowering. When the plant is in distress, what is affected is the amount of flowers it can produce, the fertility and the quality of their nectar."
Hot in the world, hot in the hive
In recent years, there have been increasing reports of early flowering in tree species growing in mountainous areas, including almonds, at unusual times. This trend is most likely the result of various weather phenomena that cause certain plant species to become confused and bloom in the months of October-November, explains botanist Prof. Avi Shamid from the Hebrew University. Disruptions in the flowering times, adds Prof. Sternberg, "may lead to a lack of synchronization in the ecosystem and damage to the mutual relations between the pollinators and the plants."
The flowering timing of different plants is affected, and then there is a mismatch between this time and the time when the pollinating insects reach them. Photo: Izhar Laufer, Flickr
The flowering timing of different plants is affected, and then there is a mismatch between this time and the time when the pollinating insects reach them. Photo: Izhar Laufer, Flickr
Global climate change is reflected in an increase in temperature that affects the level of sea water and causes extreme weather phenomena, and also brings a change in the flowering times of plants and the activity of creatures whose role is pollination, such as bees.
"The increase in temperature leads to flowering disturbances of more than one species of plants. "Not only almonds wake up early, but also annual plants from the cruciferous family - such as mustard, cauliflower and broccoli - whose flowering time is usually in the March-April region," says Prof. Izikowitz. "However, when optimal conditions exist for early flowering, the overlap between the flowering times of almonds and crucifers increases. So the pollinating bees abandon the bitter almonds in favor of plants that have sweeter nectar." In almond orchards in the US, he says, it is customary to harvest the wild flowers and thus ensure that the bees will pollinate the almond trees and that the crop will grow.
Since bees are the main pollinator of almonds, the flowering disruptions lead to them eating and pollinating less. The weakening of the bees makes them more sensitive to external influences and diseases, and the size of the population can decrease from 50,000 individuals to only 20,000.
The significance of the decrease in the number of bees is economic: they do not pollinate the plants and therefore the crops are small. However, this damage is much broader and in recent years there has been an increase in reports of beehives that have been emptied of their inhabitants (Colony Collapse Disorder, CCD). The hypotheses on the cause of this range from the use of pesticides, rising temperatures and damage to the biodiversity of wild plants. What is clear is that if the trees bloom too early and there are not enough bees to pollinate them there is a serious problem that we will all suffer from.
