Bees for Development
Honey is produced from the nectar of plants mainly secreted by glands in flowers. Bees and plants have a long evolutionary relationship with colony development intimately linked with plant flowering periods. The exact composition of honey depends on the plant sources from which it derives and no two honeys are identical. However, in most places the bees will forage on some plant sources that are not attractive or have deleterious effects either on the bees, the honey or the honey consumers. These will vary between countries but frequently nectar sources that are from plants with unpleasant tastes or that are otherwise known to be poisonous may also produce honey with a bad taste or that may be poisonous. This is a rare occurrence but in places where this type of plant is common it may not be possible to keep bees in the area at the time when the plants are flowering.
Examples of undesirable honey have most often been described in developed countries where resources have been available for this kind of research. Ragwort (Senecio jacobea) honey in the UK is an example of a toxic honey while the honeydew deriving from insects sucking the tree Coraria arborea is an example from New Zealand. An historic example, quoted from as far back as 400 BCE, is the common rhododendron (Rhododendron ponticum) where soldiers were tought to have become temporarily drunken and incapable of fighting after eating this honey - so famously lost the battle by trickery. Certain lime tree species can poison the bees themselves but do not affect people. This is because the honeybees lack the enzyme to break down the sugar, mannose, present in the nectar and which paralyses the honeybee.
However, toxicity in honey is very rare so does not need to worry consumers. The plants in question are known and usually avoided by both bees and beekeepers while poisoning of honeybees is far more often caused by the careless use of insecticides by farmers and growers. Improperly applied pesticides, especially those that are systemic, kill many thousands of honeybee colonies each year. Unpleasant tasting honey may be improved after a period of storage. However, honey from an unpleasant tasting plant source should never be included in a larger batch of honey as it can spoil it all.
On the positive side, some poor tasting honeys may have some special medicinal value. Manuka honey from New Zealand is an example of this. Manuka honey derives from the plant Leptospermum scoparium and for a long time had little markey value because of its flavour. However, research showed honey collected from this plant had medicinal properties over and above the normal medicinal value of honey. In other countries bitter or otherwise unpleasant tasting honeys may also be discovered to have additional medicinal qualities. For instance, indigenous beekeepers in Uganda and Kenya will point out a bee tree that is traditionally used as a treatment for malaria. The honey has a bitter taste so is not well liked but there is huge potential for research into possible medicinal properties from a range of melliferous African trees.
List of Articles available on this topic (1):
The use and abuse of introducing honey plants
Eisikowitch D; Dafni A