Honey Bees in the Garden: Propolis aka Bee Glue

Propolis is made from a sticky substance called resin and is produced by some plants when they suffer an injury, such as a broken limb.  It is used by the plant for protection against bacteria, viruses and other threats to the plant's health.  Honey bees collect this resin and mix it with beeswax in order to carry it back to the hive in their pollen basket.  A strong, healthy hive will store up to 1 pound of propolis during a season. 

The composition of propolis varies according to location and the plant it was collected from, but generally it consists of the following components:

Resin 50%

Wax and fatty acids 30%

Essential oils 10%

Pollen 5%

Other components 5%

Propolis is used by the honey bees for the following purposes:

Reinforcing the structural stability of the hive

Reducing vibration

Making the hive more defensible by sealing alternate entrances

Preventing diseases and parasites from entering the hive, and inhibiting bacterial growth

Preventing putrefaction in the hive

Propolis is usually dark brown, but can also be green, red, black or white, depending on the source.

The following medicinal properties are attributed to propolis:

Antimicrobal

Emollient

Immunomodulator

Dental antiplaque agent

Antitumor agent

Commercial uses for propolis are as follows:

Varnish for musical instruments

Chewing gum

Car wax: it converts fats and oils during car wax application

Here is a list of plants honey bees visit to collect resin to make propolis:       

 Cedar

 Poplar

 Fir 

 Juniper

 Pine

 Spruce

 Redwood

 Yew

Larch

Autograph tree

Mayapple

Sweetgum

Creosote bush 

Aspen

Willow 

Birch  

Alder 

Poison oak

Poison ivy

Horse Chestnut

Buckeye

Gardenia 

Quinine 

Coffee 

Morning glory

Parsley

Dill

Fennel

Caraway

Sassaparilla

Ginseng

Rabbitbrush

Balsam root

Sunflower

Tarweed

Tahomuco

Propolis is sticky at warm termperatures but becomes brittle when subjected to cold temperatures. It will return to a sticky state when warmed again.  It acts and feels like chewing gum after you've chewed it to a soft state.

Commercial beekeepers harvest extra propolis by replacing the solid inner cover with one that has a lot of holes in it.  Honey bees do not like having all those extra holes inside the hive so they fill them with propolis.  The beekeeper then takes that inner cover full of propolis out of the hive and freezes it so it will become brittle and easy to pop out of the holes.  They replace the regular inner cover once they have harvested all the propolis for the season. 

Photo credits:

Gardenia courtesy of Jan Swaney (Mekos).  Used with permission.

Sunflower courtesy of Christine (Wildflowers). Used with permission.

Sources:

Propolis

Resins