Beekeeping value of melliferous plants

The number of plant species producing nectar and pollen is very large; in Switzerland, several thousand are recorded. However, they do not all have the same beekeeping value, and only a few hundred are actually visited by bees. Among these, barely around thirty have a truly high beekeeping value, about seventy are considered secondary, and the others are of lesser interest because they are less common or occur only sporadically.

For a plant to be of interest to the bee (and to the beekeeper), certain conditions must be met:

①  The plant must produce nectar that is attractive to bees.

The attractiveness of a plant depends on the sugar content of its nectar, which varies from one floral species to another. If the sugar concentration is low, the nectar does not attract bees: nectar with a sugar content below 20% is poorly attractive and also of low energetic value. A sugar content between 20 and 35% is considered moderate, while a content between 35 and 65% is considered high, the latter being clearly preferred by honey bees.

②  The plant must produce pollen that is attractive to bees.

The attractiveness of pollen depends on its protein and amino acid content. The pollen of many plant species is not collected by bees; this is the case, for example, for the pollen of conifers and, more generally, for the pollen of anemophilous plants (whose pollen is transported by wind; from the Greek anemos = wind). These species, which also include grasses, produce light pollen in very large quantities that is easily carried by the wind and can be found far from the source plant, thus ensuring pollination of nearby plants of the same species. This pollen has low nutritional value, and the plants producing it do not secrete nectar, making them unattractive to bees (these plants do not require insect pollination). Entomophilous pollen, by contrast, is transported by insects (from the Greek entomon = insect); it is much richer, heavier and sticky, allowing it to adhere easily to the hairs of bees, which then transport it efficiently from one plant to another to ensure pollination.

③ The nectar produced by the plant must be accessible to bees.

The nectaries of some flowers are located deep within the flower and can only be reached by insects with a sufficiently long tongue. This is the case, for example, with certain clover varieties whose nectaries are inaccessible to the honey bee.

④  Melliferous plants must be located close to the hives and be present in large quantities.

A foraging radius of 3 km around the hives is often mentioned. In reality, however, bees most often do not forage much beyond 1 km; the greater the distance, the higher the consumption of honey or nectar required for flight, which reduces or completely cancels out the gain upon returning to the hive.

For nectar or honeydew harvests to be abundant, a large flowering area is required. A few lavender plants in a garden or a single fir tree in a meadow contribute very little. In contrast, for pollen, diversity matters more than quantity: even a few scattered flowers of different species are beneficial to bees, which require a wide diversity of pollen sources to meet their nutritional needs.

See also:

• Forage Plants
• How Do Bees Choose Pollen?
• Pollen Consumption and Colony Development
• Wildflower Strips Benefit Bees
• Pollen – The Unknown Worth Knowing