When bees make propolis they mix their saliva, wax produced by special glands on worker bees' abdomens, and plant resins collected from poplar trees, Clusia minor/rosea flowers, and plants in the Asteraceae family.
It's the bees living in temperate zones that typically use resins from poplar trees in order to make propolis. Therefore, the purpose of this article is to provide more information about poplar plants, since the majority of bees in the world live in these climates*.
The poplar species
Populus (poplar) is a genus contained within the Salicaceae family (also known as the Willow family). According to the Encyclopaedia Britannica, there are 55 genera in the Salicaceae family and 1,000 species of "deciduous or evergreen shrubs and trees" within that.
Poplars are the main temperate genus of the Salicaceae family and these are split into five subgenera:
- Leuce: e.g. aspens and white poplars
- Tacamahaca: e.g. balsam trees
- Aegirus: e.g. black poplars
- Leucoides: e.g. necklace poplars or bigleaf poplars
- Turanga: e.g. subtropical poplars
- Abaso: e.g. Mexican poplars
Within these five divisions, there are at least 35 species of tree, as well as some natural hybrids.
Poplars are widely distributed throughout the world but largely found in northern temperate regions including North America, Eurasia, and northern Africa. There are even some species which live beyond the Arctic Circle.
The trees in this genus grow very quickly – from one to three meters every year – depending on geographical climate, weather and species. In comparison, many trees grow just inches annually.
Canadian poplars and propolis
One of the areas in which propolis production occurs is in Canada, where bees use poplar resin gathered from the trees. Around 10% of the world's forests are located here, with 11.6% of the country's trees being poplars. According to the Poplar Council in Canada, there are 45,062,579 acres of natural (non-hybrid) species of the tree in this region.
Plant extracts from a variety of poplar species, such as quaking aspen Populus Tremuloides, bigtooth aspen Populus Balsamifera, and balsam poplar Populus balsamifera end up in Canadian propolis. This is then harvested by apiarists and used in a variety of pharmaceutical and cosmetic products, usually as preservatives in natural products to avoid the use of parabens.
Other uses for poplars internationally
The wood that poplar trees produce is relatively soft and, for this reason, is mainly used to make items such as cardboard boxes, crates, paper, and veneer for furniture.
However, these trees are also used to make sawn wood (from which other products can be made), in the carving of wooden shoes (sabots), in shipbuilding, and for making matches.
Further to these many uses, poplars have been well-liked amongst landscape gardeners and city planners for centuries – the Latin name Populus is actually a reference to the fact that these types of trees were often planted near public meeting places by the Romans.
Other related articles
If you would like to learn more about bees or the propolis they produce, the following pages might be of interest to you:
*American entomologist Charles Duncan Michener states in his book The Bees of The World (Volume One) that "Bees appear to attain their greatest abundance, greatest number of species, and probably greatest numbers of genera and subgenera, not in the tropics, but in various warm-temperate, xeric regions of the world".